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Battery Basics: A Layman's Guide to Batteries

Battery TutorialIf you have done any research on how batteries work or what you should look for when selecting the best high performance battery, you're probably buried in information, some of which is conflicting. At BatteryStuff, we aim to clear that up a bit.

You've most likely heard the term KISS (Keep It Simple, Stupid). I'm going to attempt to explain how lead acid batteries work and what they need, without burying you with a bunch of needless technical data. I have found that battery data will vary somewhat from manufacturer to manufacturer, so I will do my best to boil that data down. This means I may generalize a bit, while staying true to purpose.

The lead acid battery has been used commercially for over 100 years. The same chemical principle that's being used to store energy is basically the same as our great grandparents used.

A battery is like a piggy bank. If you keep taking out and putting nothing back, you'll have nothing left. Present day vehicle or powersport vehicle battery power requirements are huge considering all the stock electrical devices that must be supplied with power. All these electronics require a reliable source power, and poor battery condition can cause expensive electronic component failure.

Did you know that the average auto has 11 pounds of wire in the electrical system? Look at RVs and boats with all the electrical gadgets that require power. It wasn't long ago when trailers or motor homes had only a single 12-volt house battery. Today recreation vehicles use their rv batteries to power inverters up to 4000 watts.

Average battery life has become shorter as energy requirements have increased. Life span depends on usage and depth of discharge—usually 6 to 48 months—yet only 30% of all batteries actually reach the 48-month mark. If your unable to maintain the battery with an battery charger you can extend your battery life by hooking it up to a solar charger during the off months.

If you can grasp the basics, you'll have fewer battery problems and will gain greater battery performance, reliability and longevity. I suggest you read the entire tutorial; however, I've indexed all the information for easy reference.

A Few Basics

The lead acid battery is made up of plates, lead, and lead oxide (various other elements are used to change density, hardness, porosity, etc.), with a 35% sulfuric acid and 65% water solution. This solution is called electrolyte, which causes a chemical reaction that produces electrons. When you test a battery with a hydrometer, you are measuring the amount of sulfuric acid in the electrolyte. If your reading is low, that means the chemistry that makes electrons is lacking. So where did the sulfur go? It's resting on the battery plates so that when you recharge the battery, the sulfur returns to the electrolyte.


  1. Safety
  2. Battery Application: Deep Cycle vs. Starting
  3. Wet Cell, Gel-Cell and Absorbed Glass Mat (AGM)
  4. Lithium-Ion & LiFePO4
  5. CCA, CA, AH and RC; what's that all about?
  6. Battery Maintenance
  7. Battery Testing
  8. Selecting and Buying a New Battery
  9. Battery Life and Performance
  10. Battery Charging
  11. Battery Do's
  12. Battery Don'ts



You must think safety when you're working around, and with, batteries. Remove all jewelry. (After all, you wouldn't want to melt your watchband while you're wearing it!) The hydrogen gas that batteries make when charging is very explosive. We have seen several instances of batteries blowing up and drenching everything in sulfuric acid. That was no fun, and would have been a good time to use those safety goggles hanging on the wall. Heck, you could even break out your disco outfit. Polyester isn't affected by sulfuric acid, but anything with cotton will be eaten up. If you don't feel the need to make a fashion statement, just wear junk clothes—after all, polyester is still out of style.

When doing electrical work on vehicles, it's best to disconnect the ground cable. Just remember that you're messing with corrosive acid, explosive gases and hundreds of amps of electrical current.


Battery Types: Deep Cycle vs. Starting

Basically, there are two types of lead acid batteries (along with three sub categories). The two main types are starting (cranking), and deep cycle (marine/golf cart). The starting battery (SLI starting lights ignition) is designed to deliver quick bursts of energy (such as starting engines) and therefore has a greater plate count. The plates are thinner and have somewhat different material composition.

What is a deep cycle batteryThe deep cycle battery has less instant energy, but greater long-term energy delivery. Deep cycle batteries have thicker plates and can survive a lot of discharge cycles. Starting batteries should not be used for deep cycle applications because the thinner plates are more prone to warping and pitting when discharged. The so-called Dual Purpose Battery is a compromise between the two types of batteries, though it is better to be more specific if possible.


Lead Acid Battery Types: Wet Cell vs. Gel Cell vs. AGM

The gel cell and the AGM batteries are specialty batteries that typically cost twice as much as a premium wet cell battery. However, they store very well and do not tend to sulfate or degrade as easily as wet cell. Although not impossible there is little chance of a hydrogen gas explosion or corrosion when using these batteries; they are the safest lead acid batteries you can use. Gel cell and some AGM batteries may require a special charging rate. If you want the best and most versatile battery, then consideration should be given to the AGM battery type. AGM batteries are great for applications such as Marine, RV, Solar, Audio, Power Sports and Stand-By Power just to name a few.

If you don't use or operate your equipment daily, AGM batteries will hold their charge better than other types. If you must depend on top-notch battery performance, spend the extra money. Gel Cell batteries still are being sold, but AGM batteries are replacing them in most applications.

There is common confusion regarding AGM batteries because different manufactures call them by different names. Some of the more common names are "sealed regulated valve," "dry cell," "non-spillable," and "valve-regulated lead acid" batteries. In most cases, AGM batteries will give greater life span and greater cycle life than a wet cell battery.

SPECIAL NOTE: It's common for individuals to use the term "gel cell" as a generic term when referring to sealed, maintenance-free batteries, much like one would use Kleenex when referring to facial tissue. As a result, we get lots of requests for a gel replacement battery or gel battery charger when in fact the battery is an AGM. For this reason, we always recommend verifying the battery type when purchasing a replacement or looking for a charger to maintain the battery.

Wet Cell

The wet cell comes in two styles: serviceable and maintenance-free. Both are filled with electrolyte and are basically the same. I prefer one that I can add water to and check the specific gravity of the electrolyte with a hydrometer. Also, the serviceable type tends to last a little longer since you can add distilled water when evaporation occurs and treat the battery with an inhibitor such as Battery Equaliser to prevent sulfation. In contrast, with the maintenance free, you cannot do either of the servicing features.


Scorpion AGM BatteryThe Absorbed Glass Mat construction allows the liquid electrolyte to be suspended in a fiberglass matting. This matting surrounds the plate’s active material and in theory this enhances both the discharge and recharge efficiency. AGMs are commonly manufactured for applications that include high-performance engine starting, power sports equipment, deep cycle, solar and storage battery. The larger Deep Cycle AGM Batteries we sell typically offer great cycle life if recharged before they drop below the 50% discharge rate. When deep cycle AGM batteries are discharged to a rate of no less than 60%, the cycle life will generally increase by 300 plus cycles.

The Scorpion motorcycle batteries we carry are a meet or exceed the specification for the OEM battery. We also carry the Motocross branded batteries for those that have brand loyalty to the OEM battery as they are Yuasa’s aftermarket battery.


The gel cell battery is like the AGM battery in the fact that it is considered non-spillable, but the electrolyte is not a wet liquid. The electrolyte in a gel cell has a silica additive that causes it to set up or stiffen. In most cases the recharge voltage on gel battery is typically lower than a standard flooded wet cell battery or AGM battery, apart from those made by MK Battery where their 12-volt batteries can accept up to 14.6 volts. Most gel batteries can only be charged as high as 14.2 volts per 12-volt battery and are probably the most sensitive battery in terms of adverse reactions to over-voltage charging. Gel Batteries are best used in VERY DEEP cycle application and may last a bit longer in hot weather applications or application where the battery gets excessively discharged. If the incorrect battery charger is used on a gel cell battery, poor performance and premature failure is certain.

Lithium Battery Types: Lithium-Ion vs LiFePO4

The new premium battery on the market is the Lithium battery, often referred to as a Lithium-Ion or LiFePO4 battery. In most cases, they are the same battery as Lithium-Ion is the parent category of the LiFePO4 battery, so some manufacturers use the parent term vs. the specific term.

Deep cycle lithium batteries generally offer up to 3x the cycle life compared to lead acid batteries. Most are designed with a long service life of 10+ years. Lithium also offers a 60% reduction in weight compared to lead-acid batteries.

For comparison, our best lead acid battery is a Lifeline AGM battery that offers about 1000+ cycles at 50% depth of discharge. The BSLBatt Lithium Battery we carry offers over 2000 cycles at a 50% depth of discharge and up to 8500 cycles at a 30% depth of discharge. They were designed for a 15 to 18-year service life, whereas a Lifeline is estimated to have about a six year service life.

This article covers the Lithium topic from the deep cycle battery perspective. If you are looking for a starting battery, we offer plenty of choices for motorcycles, ATVs, and various other powersport applications. You can learn more about lithium batteries for powersport applications via our Lithium Battery Buyers Guide.


CCA, CA, AH and RC Explained

All of these terms are widely used by battery manufacturers. Look under the hood, and you will most likely see a battery rated with one or more of these terms. The first two in the list below are cranking terms, and the second two are capacity terms. Let's break them down!


Cold cranking amps   is a measurement of the number of amps a battery can deliver at 0°F for 30 seconds and not drop below 7.2 volts. So a high CCA battery rating is especially important in starting battery applications, and in cold weather. This measurement is not particularly important in deep cycle batteries, though it is the most commonly "known" battery measurement.


Cranking Amps are measured at 32°F. This rating is also called marine cranking amps (MCA). Hot cranking amps (HCA) is seldom used any longer but is measured at 80°F.


Reserve Capacity is a very important battery rating. This is the number of minutes a fully charged battery at 80°F will discharge under a 25 amp load until the battery drops below 10.5 volts.


An Amp/Hour is a rating usually found on deep cycle batteries and is a capacity rating. The standard rating is a based on how many amps you can pull out of the battery over a 20-hour period. For a 100 AH rated battery this means you can draw from the battery for 20 hours, and it will provide a total of 100-amp hours. That translates to about 5 amps an hour (5 x 20 = 100). However, it's very important to know that the total time of discharge and load applied is not a linear relationship. As your load increases, your realized capacity decreases. This means if you discharged that same 100 AH battery by a 100-amp load, it would not give you one hour of runtime. On the contrary, the perceived capacity of the battery will be that of 64-amp hours.


Battery Maintenance

A properly maintained battery is important for the ultimate in service life. Consider these points on a regular basis:

  • The battery should be cleaned using a baking soda and water solution; a couple of tablespoons to a pint of water.
  • Cable connections need to be cleaned and tightened as battery problems are often caused by dirty and loose connections.
  • A serviceable battery needs to have the fluid level checked. Use only mineral-free water; distilled is best as all impurities have been removed and there is nothing left that could contaminate your cells.
  • Don't overfill battery cells, especially in warmer weather because the natural fluid expansion in hot weather can push excess electrolytes from the battery.
  • To prevent corrosion of cables on top-post batteries, use a small bead of silicone sealer at the base of the post and place a felt battery washer over it. Coat the washer with high temperature grease or petroleum jelly (Vaseline), then place cable on the post and tighten. Coat the exposed cable end with the grease. The gases from the battery condensing on metal parts causes most corrosion.


Battery Testing

This can be done in more than one way. The most accurate method is measurement of specific gravity and battery voltage. To measure specific gravity, buy a temperature-compensating hydrometer. To measure voltage, use a digital D.C. Voltmeter. A quality load tester may be a good purchase if you need to test sealed batteries.

For any of these methods, you must first fully charge the battery and then remove the surface charge. We recommend letting the battery sit for several hours to remove the surface charge (I prefer at least 12 hours). Letting the battery sit gives you the most accurate result on how the battery will normally act. However, if you need to remove the surface charge faster it is possible to discharge the battery for several minutes. For deep cycle batteries you could simply power the device that uses the battery for several minutes. For starting batteries simply powering the headlight using the high beam can work as well. Once the surface charge has been removed you can begin testing.

State of ChargeSpecific GravityVoltage
    12V 6V
100% 1.265 12.7 6.3
75% 1.225 12.4 6.2
50% 1.190 12.2 6.1
25% 1.155 12.0 6.0
Discharged 1.120 11.9 6.0

Load testing is yet another way of testing a battery. A load tester removes amps from a battery much like starting an engine would. Some battery companies label their battery with the amp load for testing. This number is usually half of the CCA rating. For instance, a 500 CCA battery would load test at 250 amps for 15 seconds. However, most load testers will either allow you to input the CCA or in the case of an analog tester it will show you a graph the battery should test at.

A load test should only be performed when the battery is at near or full charge. If you don't own or want to buy a load tester, then simply charge the battery, wait 12 hours, and then take it to an automotive shop for testing. Avoid taking a discharged battery to an automotive shop for testing as the test will only indicate something you already know.

The results of your testing should be as follows:

  • Hydrometer readings should not vary more than .05 differences between cells.
  • Digital volt meters should read as the voltage as shown in this document. The sealed AGM and gel cell battery voltage (fully charged) will be slightly higher in the 12.8 to 12.9 range. If you have voltage readings in the 10.5 volt range on a charged battery, that typically indicates a shorted cell.
  • If you have a maintenance-free wet cell, the only ways to test are volt meter and load test. Any of the maintenance-free batteries that have a built in hydrometer (black/green window) will tell you the condition of 1 cell of 6. You may get a good reading from 1 cell but have a problem with other cells in the battery.
  • When in doubt about battery testing, call the battery manufacturer. Many batteries sold today have a toll-free number to call for help.


Selecting & Buying a New Battery

 When buying a new battery, I suggest you purchase a battery with the greatest reserve capacity or AH rating as possible. Of course, the physical size and terminal type must be a consideration. You may want to consider a gel cell or an absorbed glass mat (AGM) rather than a wet cell if the application is in a harsher environment, or the battery is not going to receive regular maintenance and charging. AGM and Gel cell batteries typically have a lower self-discharge rate so they can last longer when not being maintained.

Be sure to purchase the correct type of battery for the job it must do. Remember that engine starting batteries and deep cycle batteries are different. Freshness of a new battery is very important. The longer a battery sits the more damaging sulfation build up there may be on the plates. Most batteries have a date of manufacture code on them. While the date code isn’t always apparent many manufacturers or dealers will indicate the month with a letter, such as the letter with "A" being January. The letter is then followed by a number such as “4” corresponding with the year 2021. C4 would tell us the battery was manufactured in March 2021. Remember the fresher the better. The letter "I" is not used because it can be confused with the number 1.

Battery Warranties

As with most warranties, they are often favored by battery manufacturers. Suppose you buy a 60-month warranty battery, which lasts 41 months. The warranty is pro-rated, so when taking the months used against the total retail price of the battery, you end up paying about the same money as if you purchased the battery at the sale price. This makes the manufacturer happy.

What makes me happy is to exceed the warranty. As of the writing of this article, we currently carry motorcycle and ATV batteries by Scorpion and Motocross that come with a replacement warranty. For deep cycle batteries, the MK Battery and Universal Battery line currently have a 1-Year Replacement, and some of our higher-end manufacturers we carry offer higher warranty terms depending on their installed applications.


Battery Life and Performance

 The average battery life has become shorter as energy requirements have increased. Two phrases I hear most often are "my battery won't take a charge," and "my battery won't hold a charge." Only 30% of batteries sold today reach the 48-month mark. In fact 80% of all battery failure is related to sulfation build-up. This build-up occurs when the sulfur molecules in the electrolyte (battery acid) become so deeply discharged that they begin to coat the battery's lead plates. Before long the plates become so coated that the battery dies. The causes of sulfation are numerous:

  • Batteries sit too long between charges. There are two states when it comes to batteries: They are either being charged or they are self-discharging.
  • Battery is stored without some type of energy input. Even if you disconnect the battery it will still self-discharge.
  • "Deep cycling" an engine-starting battery. Remember these batteries can't stand deep discharge.
  • Not completing the charge cycle. Undercharging a battery will allow the sulfation buildup that occurred during discharge to harden. When this happens, it reduces the area on the lead plates for the chemical reaction to occur thereby reduces the capacity of the battery.
  • Heat of over 100°F increases internal discharge. As temperatures increase so does internal discharge. A new fully charged battery left sitting 24 hours a day at 110°F for 30 days would most likely not start an engine.
  • Low electrolyte level. Battery plates exposed to air will immediately sulfate.
  • Incorrect charging levels and settings. Most cheap battery chargers can do more harm than good. See the section on battery charging.
  • Cold weather is also hard on the battery. The chemistry does not make the same amount of energy as a warm battery. Also a deeply discharged battery can freeze solid in sub zero weather. We recommend gel batteries by MK Battery for subzero weather as some of their batteries are rated down to -76°F.
  • Parasitic drain is a load put on a battery with the key off. Depending on the parasitic load we have seen batteries discharged in a few days to a few months. We recommend testing your parasitic load so you know what to expect.

Increase Life

There are ways to greatly increase battery life and performance. All the products we sell are targeted to improve performance and battery life.

Battery EqualizerAn example: Let's say you have "toys" such as an ATV, classic car, antique car, boat, Harley, etc. You most likely don't use these toys 365 days a year as you do your car. Many of these toys are seasonal, so they are stored. What happens to the batteries? Most batteries that supply energy to power our toys only last 2 seasons. You must keep these batteries from sulfating or buy new ones. We sell products to prevent and reverse sulfar buildup on batteries. The BatteryMINDer products are patented electronic devices that reverse and prevent sulfation. Also Battery Equaliser, a chemical battery additive, has proven itself very effective in improving battery life and performance. Other devices such as solar trickle chargers are a great option for battery maintenance.

Parasitic drain

Most vehicles have clocks, engine management computers, alarm systems, etc. In the case of a boat, you may have an automatic bilge pump, radio, GPS, etc. These devices may all be operating without the engine running. You may have parasitic loads caused by a short in the electrical system. If you are always having dead battery problems, most likely the parasitic drain is excessive. The constant low or dead battery caused by excessive parasitic energy drain will dramatically shorten battery life. If this is a problem you are having, check out PriorityStart! battery switches to prevent dead batteries before they happen. This special computer switch will turn off your engine start battery before all the starting energy is drained. This technology will prevent you from deep cycling your starting battery.


Battery Charging

Remember, for proper battery maintenance you must put back the energy you use immediately. If you don't, the battery sulfates, which will affect performance and longevity. The alternator is a battery charger. It works well if the battery is not deeply discharged. The alternator tends to overcharge batteries that are very low and the overcharge can damage batteries. In fact, an engine-starting battery on average has only about 10 deep cycles available when recharged by an alternator. Batteries like to be charged in a certain way, especially when they have been deeply discharged. This type of charging is called 3-step regulated charging. Please note that only special smart battery chargers using computer technology can perform 3-step charging techniques. You don't find these types of chargers in parts stores or big box stores.


  1. The first step is bulk charging, where up to 80% of the battery energy capacity is replaced by the charger at the maximum voltage and current amp rating of the charger.
  2. When the battery voltage reaches 14.4 volts this begins the absorption charge step. This is where the voltage is held at a constant 14.4 volts and the current (amps) declines until the battery is 98% charged.
  3. Next comes the Float Step. This is a regulated voltage of not more than 13.4 volts and usually less than 1 amp of current. This in time will bring the battery to 100% charged or close to it. The float charge will not boil or heat batteries, but it will maintain the batteries at 100% readiness and prevent cycling during long term inactivity. Note: Some gel cell and AGM batteries may require special settings or chargers.


Battery Dos

  • Think Safety First.
  • Do read entire tutorial.
  • Do regular inspection and maintenance, especially in hot weather.
  • Do recharge batteries immediately after discharge.
  • Do buy the highest RC reserve capacity or AH amp hour battery that will fit your configuration.


Battery Don'ts

  • Don't forget safety first.
  • Don't add new electrolyte (acid).
  • Don't use unregulated, high-output battery chargers to charge batteries.
  • Don't place your equipment and toys into storage without some type of device to keep the battery charged.
  • Don't disconnect battery cables while the engine is running (your battery acts as a filter).
  • Don't put off recharging batteries.
  • Don't add tap water as it may contain minerals that will contaminate the electrolyte.
  • Don't discharge a battery any deeper than you possibly have to.
  • Don't let a battery get hot to the touch and boil violently when charging.
  • Don't mix size and types of batteries.

While that was a detailed look at battery types and how to maintain them, there's always more to learn.

Choose Your Battery

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351 people commented, TECH, Steven, Joslyn Schicchi, Tech, and 347 others
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  • Steven
    Just trying to understand the AGM batteries behavior. I have 8-6v batteries used for a small solar system of 48v. When charging the batteries get up to 57v, but when discharging they start out at 50v and then slowly discharge. Why does it start discharging at such a low voltage

    Reply  •  Rated article 5  •  January 19, 2023 at 6:42 pm
    • TECH
      While a 48v system may charge in the 59v range and float and maintain in the 56v range, they are still considered 100% fully charged off the charger at 50.92v. So, depending on the load, a voltage reading of 50v would seem perfectly normal. While it is good to know how your battery reacts under load, knowing the recovery voltage and how to interpret the voltage in terms of capacity is also important. In a 48v system, it is considered 50% discharged when the voltage reaches 48.4v in an open circuit reading.

      Reply  •  Rated article 5  •  January 23, 2023 at 1:44 pm
  • Joslyn Schicchi
    I have a 2009 tao tao moped with a TPE Lithium Motorcycle Scooter Battery. im having issues getting it connected again when j do screw thevterminals in therss no power i also did charge after use

    Reply  •  Rated article 5  •  October 13, 2022 at 10:08 pm
    • TECH
      Unfortunately, we do not sell that brand, but it sounds like the battery has been excessively discharged if there is no voltage. I suggest contacting the supplier and talking to them regarding their troubleshooting steps. Typically, you will need a lithium charger with a safe recovery mode, such as the Optimate TM-471 we sell, but I would follow up with them before purchasing anything.

      Reply  •  Rated article 5  •  December 13, 2022 at 12:16 pm
  • Steve Z
    Does a deep cycle lead acid battery discharge faster than it charges? I ask because I am using an 80ah battery to power the small refrigerator in my camper when I’m boondocking. I have a 200w Solar suitcase and a 100 watt panel on the camper. Their controllers are often in a “float” or “full” state when the sun is out and the fridge is on - indicating the battery won’t take any more charge. But the battery monitor shows it is just at 60 or 70 percent capacity. Does this make sense? Thank you!

    Reply  •  Rated article 5  •  July 7, 2022 at 6:53 am
    • BatteryStuff Tech
      Steve, as far as if a battery discharges faster than it charges depends on the amperage being pulled from a battery and the amperage charging the battery. Typically, most smart chargers will taper off the amperage towards the end of the charge to not heat the battery, so that can add about 10 to 20% extra time than the straight math might indicate. However, I think your issue might be a different problem. It sounds as if your controller is shutting down prematurely or is set to go to a float mode after it has been charging for a certain amount of time. I would suggest contacting the manufacturer of the controller to determine why it would be going into float mode when the battery is not full. You may also consider an MPPT controller such as our Victron Controllers as they can be programmed via a smartphone and give you more options to control your charging.

      Reply  •  Rated article 5  •  July 8, 2022 at 1:05 pm
  • Carl Oh
    Hi great article…I have a TT with 2 trojan 6v batteries hooked up to a renogy 30amp controller and a lg 350 solar panel When I hooked them up at the beginning of year the hydrometer reading was 1265. Now the reading is 1225 but the controller says 100% 13.4v. I have been watching and the controller does boost and float and is always at 100%. Why is the hydrometer reading in the recharge area. The whole system is only 1 year old.

    Reply  •  Rated article 5  •  June 29, 2022 at 4:02 am
    • BatteryStuff Tech
      Carl two things maybe happening... The batteries could be sulfated and while the controller is able to bring them full charge the batteries will not hold their after they are disconnected. Or, the controller is simply not charging the batteries correctly. I would suggest charging the batteries with your normal plug in charger and see if it is able to get the batteries to full charge with a good specific gravity reading. If it is then you know the solar charge controller isn't functioning properly. If it isn't then you know your batteries maybe sulfated.

      Reply  •  Rated article 5  •  July 1, 2022 at 7:44 am
  • Albertnok
    Bravo, seems to me, is a remarkable phrase

    Reply  •  Rated article 5  •  November 22, 2021 at 8:36 pm
  • Alex
    Do I need to disconnect battery banks to measure CCA? I have (2 x 12v in serie) x2 of this in parrallel. So basicaly 24v with 4 x 12v batteries.

    Reply  •  Rated article 5  •  November 1, 2021 at 9:40 am
    • BatteryStuff Tech
      In parallel you are going to get double the CCA, so you may want to disconnect the parallel connections to measure your CCA with a tester. Once the parallel connections are removed you can test each battery individually even with the series connections in place as the tester will only see what is in-between the testers positive and negative connection.

      Reply  •  Rated article 5  •  November 1, 2021 at 10:08 am
  • Tim
    I have a flat plate AGM Deep cycle 135aH battery. It's brand new and is sitting at 13 volts. I recently bought a load tester off ebay and when I go to load test the battery it is asking for the CCA. How do I calculate the CCA if the CCA is not displayed on the battery sticker? I assume the CCA is not displayed because this battery is not a cranking battery.

    Reply  •  Rated article 5  •  October 12, 2021 at 7:57 pm
    • BatteryStuff Tech
      The easiest method might be to contact the manufacturer of the load tester as they may have a AH to CCA conversion table for testing deep cycle batteries with their load tester. We sell a PulseTech unit that has such a table, but if your manufacturer doesn't you can simply contact the manufacturer of the battery in question as they often have a CCA specification on file even if it is a deep cycle battery.

      Reply  •  Rated article 5  •  November 1, 2021 at 9:14 am
  • Andy Schouteten
    We have an off gritt solar system that supports a home with 240v electricity for fridge, dishwasher, washing machine and all lighting. We have around 3kw of solar panels and a 2,5 kw inverter. We store electricity in 24 6v 225ah lion batteries. We are thinking of replacing these batteries because they are more than 10 years old. We also would like to reduce the number of batteries but still have the same or better storage capacity. What would be your recommendations

    Reply  •  Rated article 5  •  October 9, 2021 at 9:18 pm
    • BatteryStuff Tech
      Unfortunately, we don't specialize in deep cycle lithium batteries at this time. I would suggest contacting another source if your still looking to stick with lithium.

      Reply  •  Rated article 5  •  November 1, 2021 at 9:29 am
  • Jim Navotney
    And despite all the youtube videos never runn your engine with the car battery dissconnected

    Reply  •  Rated article 4  •  October 5, 2021 at 4:37 pm
  • Eileen McCracken
    This is helpful. For the existing deep cell in our rv we should not use more than 50% of charge. If we upgrade to agm can we use more? Reading the article there are a lot of maintenance and life span advantages but I’m not clear if I can run my fridge longer! Thanks so much

    Reply  •  Rated article 5  •  September 19, 2021 at 9:00 am
    • BatteryStuff Tech
      AGM's can hold under higher amp loads at lower depths of discharge, but they are still considered a lead acid battery and do not like being discharged below 50% as it effects their cycle life. The fridge may be able to run longer when the battery is getting excessively discharged, but the batteries cycle life will still be drastically affected anytime you take the battery below 50%. If you plan on excessively discharging the battery below 50% you may want to consider a gel battery as they withstand excessive discharge better and tend to start with a higher cycle life.

      Reply  •  Rated article 5  •  November 1, 2021 at 11:12 am
  • Dhika R
    I've got a 100 ah battery (i'm told by the ebay seller its gel) that has a maximum voltage of 15v similar to an AGM written on the case. Its still brand new and I wanted to get a second one to wire in series but found out that they are not selling this product anymore. I wonder if I can get away with a 100ah AGM battery as the second unit in series. Also wondering if this battery is actually a gel cell if it has a maximum voltage of 15v. Thanks The battery is an eco-worthy VT12100 (green)

    Reply  •  Rated article 5  •  May 10, 2020 at 6:03 pm
    • BatteryStuff Tech
      We would not recommend putting batteries together unless they are the same type, age, and chemistry. Basically, they should be the same battery from the same batch otherwise they will never be balanced to each other, which can lead to a battery failure.

      Reply  •  Rated article 5  •  May 11, 2020 at 8:47 am
  • Brian Ap
    I use two lead acid batteries of field charging of hobby batteries. I bought a min kota digital precision dual bank charger to charge them. This charger uses what they call a "mild equalization phase" in the bulk charge cycle. I have come back to find the charger stuck in this phase for over 24 hours. Basically it can never get past this part and there is no fault timer to kick it out of this phase. I noticed that the batteries were boiling in this phase so I stuck a voltmeter on to see what it is doing. What they call " mild equalization" is just going up to 14.7 volts for the bulk phase. The charger is obviously looking for something to get past this phase. I can only guess that it wants to see some higher voltage to move on to the float charge. I was very annoyed that it would just go ahead and boil off most of the water with no signs of stopping. When I called tech support they said that I must just have worn out batteries since they don't have a problem with this line of charger. Are my batteries to blame or is the charger wearing them out by bulk charging at 14.7 V? They were 4 yrs old at the time and could indeed be "old".

    Reply  •  Rated article 5  •  May 7, 2020 at 3:12 pm
    • BatteryStuff Tech
      It could be either the charger or the batteries. Most marine smart chargers have built in time limits to prevent chargers from being in operation for extended amounts of time. Unfortunately, it sounds like yours doesn't have that feature, so it might be wise to look at getting an new charger in the end just to prevent this issue from arising. If you would like a recommendation feel free to contact our tech department. Eithew way I would also suggest taking your batteries to a local battery shop to have them tested, so you can determine if it is the charger or the batteries.

      Reply  •  Rated article 5  •  May 11, 2020 at 12:36 pm
  • Jack Martin
    What minimum voltage is acceptable for a 12V AGM (and other lead-acid) batteries upon receiving after shipment? The issue came up when I received a "new" AGM battery that arrived at X volts, and it seemed too low for a proper storage voltage, suggesting the battery may have arrived already a bit damaged.

    Reply  •  Rated article 4  •  March 25, 2020 at 10:29 pm
    • BatteryStuff Tech
      A lot depends on where you are getting the battery. If the battery comes from our store like us, then chances are the battery is going to be load tested prior to it leaving the warehouse to ensure the battery is good. Our 100 Amp load test can take anywhere from 5% to 25% off the battery depending on the battery size. This means the battery may be received by the customer between 12.3 to 12.6 volts. If the battery comes from a big box retailer or online store that's primary focus isn't batteries, then chances are the battery isn't being tested. If the battery arrives discharged from these type of stores it would most likely indicate that it has been sitting on the shelf for awhile, or stock wasn't being rotated correctly. So, the real question is what the voltage is 12 hrs after its been charged? That voltage will give you a good indication on the state of the battery and if it is sulfated. Ideally, any battery with an open circuit voltage of 12.7 volts or higher for a 12v battery is considered 100%. However, very fresh and new batteries will typically have an open circiut voltage of 12.9 to 13.2 volts 12hrs after charge.

      Reply  •  Rated article 5  •  March 27, 2020 at 7:58 am
  • Michael Trivette
    I have a Kangaroo golf cart and it recommends a 12v Deep Cycle Gel with a minimum 31ah. What battery and charger do you recommend. The current one does not hold a charge for an entire 18 holes of golf. Thank you.

    Reply  •  Rated article 5  •  March 21, 2020 at 5:16 pm
    • BatteryStuff Tech
      Michael, it is hard to give a recommendation with the information given... Ideally, you do not want to discharge your battery beyond 50%, otherwise you would be excessively discharging the battery. This means if you want to play 18 holes of golf your battery should be able to withstand that, and still be at least 50% charged when you get back home. The manufacturer of your cart has given you are minimum recommendation, but if you can't even get through a round of golf on that recommendation, then you need to figure out approximately how far you have gone. Let’s say you done 14 holes and your battery has gone dead. This means the golf cart lasted 77% of the course leaving 23% left. In the end you need a battery with 146% higher in capacity than your current battery. Basically, you are doubling your 77%, which is the 100% increase, and you still have 23% more of the course left to play, so 46% is the extra 23% left on the course plus the extra needed not to discharge the battery below 50%.

      Reply  •  Rated article 5  •  March 23, 2020 at 8:52 am
  • DennisoxYpe
    I simply wish to say I am newbie to blog and actually relished you're site . Most likely I'm want to bookmark your website. You certainly come with great posts. Thanks a lot for exposing your blog website.

    Reply  •  Rated article 5  •  February 15, 2020 at 8:55 am
  • CraigDiunk
    Thanks pertaining to delivering this manner of terrific posting.

    Reply  •  Rated article 5  •  July 26, 2019 at 1:29 pm
  • C Joseph
    This article was outstanding the best I've ever read regarding everything you want to know about the various types of batteries, functions, etc. Thank you. Good job!

    Reply  •  Rated article 5  •  December 30, 2018 at 5:09 am
  • JaimeOxync
    Good post! I read your blog often and you always post excellent content. I posted this article on Facebook and my followers like it. Thanks for writing this!

    Reply  •  January 18, 2017 at 8:28 am
  • Jerry
    I have a Ford Transit with a single battery system. I also have a 1000 Watt inverter that I use to keep my phone and laptop charged. I have drained the battery to the point it will not start the Transit so I am trying to add additional power to keep from drawing the battery down for a longer period of time. After reading your article, it sounds like I should avoid drawing the vehicle battery down too low. Would you recommend dual batteries, a deep cycle battery, or…? I would greatly appreciate any ideas. Thank you!

    Reply  •  January 15, 2017 at 4:49 pm
    • BatteryStuff Tech
      If the battery is going to be inside the vehicle we recommend an AGM battery or Gel battery. If you plan to have the vehicles alternator to charge the battery your best bet is to go with an AGM. You would need to isolate the vehicle battery from auxiliary battery using a Battery Isolator. Be aware that if you plan to go this route the chemistry of the vehicle battery, and the auxiliary battery need to be the same, otherwise the isolator may overcharge one battery.

      Reply  •  January 17, 2017 at 10:26 am
  • Nate
    What is your advice on the best battery for a backup sump pump application?
    From 0 to 2 times per year our AC power goes out when it is raining.
    Perhaps once every 5 years it goes out when Niagara Falls is flowing into our sump pit.
    When this occurs is it profoundly essential the backup system work.
    Most backup sump systems appear to be sold with 12V maintenance free deep cycle 75 or 100 AH AGM batteries.
    Does this seem like the best choice?
    Also, the systems are sold with controllers that charge the batteries occasionally. I assume this is important to obtain maximum battery life. Any advice here on ways to ensure periodic charging is occurring?
    Finally, any other overall advice?
    thanks much

    Reply  •  June 24, 2016 at 6:51 pm
    • BatteryStuff Tech
      I find most people with sump pumps have at least a 100 AH battery, but it is best to go with whatever the manufacturer recommendation at a bare minimum. The higher the capacity the longer your pump can run if AC power goes out. As far as the charger is concerned we recommend a power-supply / converter chargers if the battery will be in use while charging. Most sump pumps will come with a charger that has demand sensing technology, so you don’t end up overcharging your battery. However if your charger ever goes out, and you need to replace, be sure to get one that does work as a power-supply / converter charger, otherwise you may overcharge some batteries and learn the lesson the hard way.

      Reply  •  January 18, 2017 at 1:02 pm
  • Mohamed Omer
    This article is very helpful for me. But i have one more qn to ask. I bought a new 12v 200Ah battery.but there is no electrolyte.just empty. I poured distilled water and made to charge.after two days the plates getting coated with some white what shud i do me please.

    Reply  •  Rated article 5  •  June 22, 2016 at 12:48 am
    • BatteryStuff Tech
      Really hard to say what happened, as someone could have already contaminated the battery before you.

      Reply  •  January 18, 2017 at 7:13 am
  • Kwaku
    How can one determine the number of plates in a battery by the batteries amp-hr? Is there a formulae to calculate the number of plates in a battery? Thanks

    Reply  •  June 20, 2016 at 9:07 am
    • BatteryStuff Tech
      There is no correlation between the to for such a calculation. Capacity generally follows the amount of lead in the battery, so the more lead the higher capacity.

      Reply  •  January 17, 2017 at 12:04 pm
  • Dilawar
    Sir i have a sunlight dry battry of 2volt 300amp, it is dead how can i recharg again.

    Reply  •  June 12, 2016 at 1:13 am
    • BatteryStuff Tech
      Generally those batteries are recharged in a battery pack of at least 12v, so you would need more than one battery in order to recharge in most situations.

      Reply  •  January 17, 2017 at 10:18 am
  • Jason M.
    Excellent resource. Great writeup. Thanks for sharing your knowledge with the world.

    Reply  •  Rated article 5  •  May 28, 2016 at 12:04 pm
  • Kevin
    I am installing a 36 volt trolling motor and it calls for 6 gage wire. The boat had a smaller trolling motor installed on it previously and it had 2 , 10 gage wires together for the positive and 2 , 10 gage wires together for the negative . Will 2 10’s be sufficient to carry the amp load of a 6 gage or do I have to replace the 4 10’s with 2 , 6’s . Total lengths is 20 feet , but that should only affect voltage drop

    Reply  •  May 7, 2016 at 9:21 am
    • BatteryStuff Tech
      The amperage your motor pulls may be the reason the manufacturer suggest 6 gauge wire to be the best selection. I know out of experience that our 10 gauge custom cable that is 8ft long only handle up to 30 amps. Given your distance and the amperage the motor pulls you could very well need the 6 gauge cable. If you are looking to substitute with a different gauge i would suggest talking with the manufacturer.

      Reply  •  Rated article 5  •  May 9, 2016 at 8:22 am
  • Derek
    I have a 100ah agm battery in my caravan which has buckled and wont hold a charge.
    I am about to buy a new agm battery but hope you can advise me on the following.
    When I head off on a trip I have the battery fully charged. I have an Anderson plug charging the battery whise we are driving, the question is, can a fully charged agm battery be damaged by overcharging by the charge it receives from the car while I am driving.

    Reply  •  April 25, 2016 at 5:16 pm
    • BatteryStuff Tech
      We recommend that you use a Battery Isolator when charging through the alternator so you don’t overcharge a battery. They are designed to charge not only the caravan’s battery in your case, but an additional battery pack. The key thing you need to know with isolators is that you need to match the chemistry so that it knows how to charge the battery correctly. Another words if you have an AGM battery for your house battery, then you should have an AGM under the hood as well. This will ensure the isolator charges the batteries correctly and doesn’t overcharge the battery. I have heard of isolators that can determine the charge if chemistry doesn’t match, but they are extremely expensive, and I’m not sure how reliable they really are. It is best to just match chemistry in my opinion.

      Reply  •  Rated article 5  •  April 26, 2016 at 8:57 am
  • Dave Brennan
    I built a paddlewheel for my pontoon boat using motors from a power wheelchair. I used the original batteries from the chair.2×12=24v.will I burn out the motors by changing to full size batteries or is 24 volts 24volts ?

    Reply  •  Rated article 5  •  March 18, 2016 at 4:50 pm
  • Dean
    Im a designer/installer and have read literally hundreds of guides and tutorials over the years and none are a patch on this – hats off, you’re brilliant – and crazy helpful to have provided answers to every question posted here individually, for free, despite you having already answered 99% of them in your other excellent articles!

    People, don’t be lazy, sure this guy has a life so read ALL the FREE guides provided for you here before asking. Big respects

    Reply  •  November 20, 2014 at 11:09 am
  • Mike Coshan
    Fantastic article though I admit even the laymans terms seems to go over my head. I live in the UK and have a QUICKIE Jive Midwheel drive wheelchair made by Sunrise Medical which uses 2 × 12volt 70 amp sonneschein GEL Batteries I Have a 8amp Gel battery charger but in the 27 months I have owned the chair I’ve had to have 4 sets of replacement batteries as they fail after 6 months apparently ( according to the manufacturer) because of a faulty Cell. I have followed the manufacturers guidelines with charging the battery, which states as soon as you’ve finished using the chair put it on charge. . Though I often wait about 5 hours to put the chair on charge. I do this and then leave it. So the chair gets between 13 & 18 hours charge even if I have done only 5 miles, which is my about my average daily use. Should I put the chair on charge straight away the leave it alone even If I need it? I have my manual wheelchair to get about in inside my house. Any help to prolong the battery life is greatly appreciated. I have repeatedly asked both Sunrise medical & sonneschein for help over the past 2 years with n how to alleviate this problem but have had no reply.

    Reply  •  Rated article 5  •  November 19, 2014 at 2:16 am
    • BatteryStuff Tech
      I would definitely not leave the batteries sitting in a discharged state, plus it is never recommended to discharge a battery more than 50% so if your 5 mile run does this then that could be affecting the batteries life. If you are not running them below 50% then I would look to the charger, and be sure it is at least a 3 stage charger, anything less is not recommended for those size batteries. Feel free to contact our Tech Department for assistance.

      Reply  •  Rated article 5  •  November 19, 2014 at 2:56 pm
  • BatteryStuff Tech
    The rating reflects how many amps you can pull from that battery over a specific period of time. In general the ratings goes down the quicker you pull a load out of a battery, so a 200AH 10 Hr rated battery will have a higher capacity than a 200AH 20 Hr rated battery.

    Reply  •  Rated article 5  •  November 18, 2014 at 11:30 am
  • Kanzi
    I am in the process of upgrading my solar electricity in my house and need information regarding what electrical appliances 8 AGM batteries will be able to power. I already have a solar panel array in place that is powering a solar water pump very effectively. I suppose I need to tell you the amount of watts the panel produces but do not have that info. at this time. Is it likely that I can replace my propane frig. with an electric refrigerator, run power tools without the generator on, etc.?

    Thank you!


    Reply  •  Rated article 5  •  November 8, 2014 at 9:00 am
    • BatteryStuff Tech
      As solar is basically a math problem I would suggest reading our article Solar Systems The Right Way as a start, or Contact Our TECH Department for further assistance. Please be aware that we are not home solar experts, and it might be best to contact a local home solar expert.

      Reply  •  Rated article 5  •  November 19, 2014 at 11:58 am
  • DaveT
    Great article. However, it seems that no matter how many articles I read on batteries, I can’t seem to grasp a full understanding of how it all works. And I say that because 6 years ago I purchased a highly modified EZ-GO golf cart that I use to get around the woods of southwestern Pa. year round. Our temps run in the high 80’s in the summer to the mid teens in the winter, and at times lower. I have a 48-volt system using 8 six volt T-105’s and a smart charger for the cart, and for my headlights and winch a separate vehicle 12-volt battery. Now, I’ve read that I should not discharge my flooded T-105’s below 50%, but in all honesty, that is at times impossible to do. The woods are not that short in places, and at times…well mud is mud and you can’t predict it. However, I always check my water levels…they seem to remain a constant…and I always clean my terminals monthly, even if they don’t seem to need it. Your suggestions of using grease is great and I will do that on my next cleaning session. Now, I have installed a new Warn winch and I winch my cart on and off my truck. I currently have one 12-V auto battery in the cart, but I am concerned that I may be “out there” and the 12-V simply run out of charge. So, what I have been thinking of is replacing the one 12-V with two 12-volts and wiring them to still have a 12-volt output, but have a longer output “time” if you understand what I’m saying. I have enough room under the cart seat for the average width of a car battery, and about 24” in length. What type of batteries would you suggest would work the best in my situation?

    Reply  •  Rated article 4  •  October 18, 2014 at 10:18 am
  • Earthrealm
    lease, am a little confused. whats the difference between a 200ah 20hr rated battery and a 200ah 10hr rated battery. am trying to buy a deep cycle battery and i see 10hr on one and 20hr on the other. which one is better?

    Reply  •  October 16, 2014 at 2:46 am
  • Stella
    Thank you so much for writing this. I am certainly going to give to my husband to read and for reference. I just purchased a yamaha 36v golf cart that needs new batteries. There are 6 each, 6 volts batteries, which would you suggest?

    thank you !

    Reply  •  October 14, 2014 at 8:09 am
    • BatteryStuff Tech
      We carry some of the best Golf Cart batteries available. Any of the batteries listed in our Golf Cart Section would be recommended.

      Reply  •  Rated article 5  •  November 18, 2014 at 10:39 am
  • Darren
    Hi, I have been getting a headache with all the conflicting advice on my current and planned dual battery setup. I have a 105 Landcruiser with 4.2 diesel and standard 110 amp alternator. I have a dual battery system with a Delkor 27HR-70 Calcium and a brand new Optima Blue Top D27M AGM (replaced the other Delkor which died) as the secondary battery for running utilities (fridge etc). They are parallel connected through a RedArc 100 amp isolator. I also have a RedArc 120W portable solar setup to assist with powering for extended camping etc.

    Firstly, is this current setup likely to damage Optima through lack of charging output. And if so would an in car BC/DC charger resolve the issue.

    Secondly, as I am not sure of the age / condition of the Delkor I am thinking of replacing it with a new Optima Yellow Top D27F. Would this make my current setup sufficient? Or is the standard 110 amp alternator still not up to fully charging the AGM’s?

    Would really appreciate some feedback and guidance



    We would require more information about your situation.  Please contact one of our techs at

    Reply  •  October 3, 2014 at 7:56 pm
  • Suz
    Wow…thankyou for existing. We are beginning to get a solar set up organised for free camping and I have a plethora of questions that hopefully you can answer for me. We intend to run a 12v52 litre fridge and strips of led lights. What do I need to know about these applicances when planning the battery set up. We are looking at a 12v 260 AH AGM battery using a 140W solar panel to charge. Would one battery be enough or should we look at two – the fridge needs to run most of the time but the led lights would be just at night. If we did get two what is the difference between wiring in series and in parallel ….is one way better than the other?? And I need reminding … In paralel is it positive to posiive and neg to neg.. Thank you so much for your time and expertise……cheers Suz from Oz

    Reply  •  September 20, 2014 at 4:12 am
    • TECH
      Suz I would suggest reading our article: Solar Systems the Right Way. This will help you gather the proper information to determine if your panel and battery setup would be sufficient. As far a series vs parallel I suggest looking at our article: Battery Bank Tutorial – Series and Parallel. This article will show you possibilities of creating different type of battery banks, and maybe the possibility of going to two 6 volts batteries for less than two 12 volts batteries would be for the same Amp/Hr capacity.

      Reply  •  September 26, 2014 at 12:44 pm


    Reply  •  September 16, 2014 at 2:22 pm
    • TECH
      If your existing battery is a WET cell then you can use an AGM. However if your original battery was a GEL then you would have to contact BMW to verify that your charging system will charge and AGM as they charge at a higher rate.

      Reply  •  September 25, 2014 at 11:11 am
  • Kyla
    Great article, easy to understand and informative. I have a few questions about my RV battery cables. I was about to replace the 2 12v marine batteries on my RV with 2 6v deep cycles, when I realized the cable situation seems strange and possibly scary.

    - The ends of the cables, for about a foot before the terminal connectors, are all taped up and homemade. Should I be concerned about that? – How do I know if they’re an appropriate size for the battery size? – There is a thin black ground wire coming from the taped up part of the + cable, which is bolted to the trailer frame. Why would the + cable be grounded? Isn’t that what the – cable is for?!

    The 2 cables that were used to connect the 12v batteries in parallel are also of this taped-up homemade variety. I was going to use one of them to connect the 6v in series, but now am unsure whether I should use ANY of these cables at all. Wiring in new cables seems really daunting because I can’t see an obvious way to access where they run up into the bottom of the trailer. But I don’t want to be unsafe, so…

    Thanks in advance :)

    Reply  •  Rated article 5  •  September 5, 2014 at 3:17 pm
    • TECH
      I would talk to your local RV Service Center if you feel the homemade cables are questionable. If you plan on rewiring the the connections to replace the existing cables we recommend staying with the same gauge wire that originally came with your RV. Obviously the last foot or so you said is homemade, so you would want to look further up to see what size the original cable is. If your changing charger, converter, or inverter (or an all in one) then we recommend you look to that manufacturer for recommendation.

      Reply  •  Rated article 5  •  September 25, 2014 at 9:48 am
  • Joel
    Hi, I bought a sailboat with 2 batteries and a selector which reads off/1/both/2
    My question is about what you say about batteries being the same size, rating and type. Of the 2 that came with the boat, #1 is a reg. acid starting battery and #2 is a deep cycle used as a house battery. Is that bad? should I avoid the “both” position of the selector?

    Reply  •  Rated article 5  •  September 4, 2014 at 10:31 am
    • BatteryStuff Tech
      Good Question! The selector switch is designed to get the boat out of a bad situation, say for instance you were unable to start the boat. This enables you to bank the other battery together in such situation to get the boat going again. You do want to avoid tying them toghether unless your are in a problematic situation.

      Reply  •  Rated article 5  •  September 12, 2014 at 12:37 pm
  • Maurice
    If AGM batteries aren’t damaged by a car’s alternator charger why do they need a special charger?

    Reply  •  August 23, 2014 at 6:45 pm
    • BatteryStuff Tech
      They really only need a specific charger if they are being maintained long term with a constant charger. The exception is specialty AGMs such as Odyssey batteries or aircraft batteries.

      Reply  •  August 25, 2014 at 2:36 pm
  • T-Man
    Thank you for some great info. We have a travel trailer that we have parked at a camp area on the back the farm. It hasn’t moved since we bought it 5 years ago. We charge the battery with a Honda 3000 generator. After many years of frustration using a flood cell deep cycle battery we just installed a AGM battery. (I believe we brought the charge down on the batteries too far, too often). Anyway we just bought the AGM battery because we understand it will charge much quicker than a flood cell. My question is using this type generator on a trailer, will that work for a AGM or should we do anything different for charging?
    Thanks again.

    Reply  •  August 16, 2014 at 11:39 am
  • Laura Hargis
    We have a John Deer Gator (riding toy)for our Granddaughter. The connection for the battery has corroded down inside. Is there a safe way to clean it out? It is a very tight area.

    Reply  •  July 23, 2014 at 12:35 pm
    • Admin
      Baking soda and water, but not in the battery!, just for the terminals and connections.

      Reply  •  August 15, 2014 at 2:14 pm
  • Md. Saiful Haque Khan
    I have two 12v 100AH battery it is connected with IPS recently I see the battery is very HOT & IPS Full Charge indicator not showing full charge. I check Battery Water Level ok. Then I disconnect all battery from IPS 2 days take time to cool the battery & after battery fully cold I connect it to IPS but again the battery is very HOT. What is just happening Can you tell me please.
    My battery Name Lucas AP 100 12V 100AH 21 Plate made by Rahimafrooz Bangladesh. Please give me the repply. Thanks
    Saiful Haque Khan

    We would require more information about your situation.  Please contact one of our techs at

    Reply  •  July 18, 2014 at 1:06 pm
  • GarthJ
    I have a boat with a normal marine 12v lead acid battery I would also like to add a second battery to provide for lets say a 12v access port for accessories. Unfortunately I have limited space for a second full sized battery. Could I use a smaller lets say ATV type twelve volt battery connected through a dual battery charger relay isolator so that both would charge when the motor is running but both would not drain when the motor is not running.

    We would require more information about your situation.  Please contact one of our techs at

    Reply  •  Rated article 4  •  July 15, 2014 at 9:58 am
  • ArieS
    I have a few questions on battery reconditioning, based on reading of various How To and DIY sites, and hope that you are able to help: 1 – The powder that everyone seems to suggest is Epsom salts, is that correct? 2 – Is there a specific type of these Epsom salts that is appropriate? 3- What are the mixing specs for the solution? Thanks a lot!


    We would require more information about your situation.  Please contact one of our techs at

    Reply  •  Rated article 4  •  July 8, 2014 at 2:50 pm
  • Tracy
    I have installed a few advanced GPS devices on a fleet of vehicles. The manufactures paperwork says they should be wired into an output capable of at least 13 volts. I have not had any problems with the devices on vehicles with a normal 12 volt car battery and wonder if there would be any possible problems if I wanted to install them on a recreational vehicle like a Polaris ATV/Quad or a Side X Side with a 12 volt battery?

    Reply  •  June 26, 2014 at 12:50 pm
    • BatteryStuff Tech
      It should work fine, but always check with the manufacturer for a hard answer.

      Reply  •  June 27, 2014 at 8:48 am
  • Zareef
    I had solar system, Know I want to add new set of batteries with old one for charging purpose, both pared as 24V sets. 24V old set and 24v new set. is this work or any problem, i will face during charging for solar panels.
    or should i charge separtly and use dual purpose. Once charge new and than Old.

    In house for electric city,Should i combine both sets, or I use old to discharge than switch to new for use.

    Reply  •  Rated article 3  •  June 14, 2014 at 11:37 am
    • BatteryStuff Tech
      I would recommend charging separately. Mixing old and new batteries is asking for trouble.

      Reply  •  June 16, 2014 at 11:04 am
  • Randy
    We have a few 10 tonne dump trailers that are towed behind a few chev 2500 3/4 ton trucks (1 alternator)1 battery. Also towed by 2 ford 1 tons which have dual batteries in them.
    We are using deep cell wet batteries 175AH (D27’s) one battery in each trailer. The batteries in the trailers only get a 1/2-1 hour charge from the 7 way trailer plug when they are ran to site and dumped. I don’t have the amp draw of the “Dyna-Pack) electric/hydraulic motor/pump unit yet. It takes 15-30 seconds to fully dump the trailer. The batteries don't seem to last too long to these guys. The charge from the tow vehicle may be to low as the voltage drop in the 12 or 14 ga. wire used in the typical trailer tow package. I was thinking about wiring in #4 ga. from the font to the rear trailer with a battery isolator so the trailer battery could receive a better charge rate., specially if being dumped every hour or two and only getting 1/2 or little more charge in between. Is it worth it $150 + isolator. I can install and get reasonable pricing on wire & terminals etc. Also what is the best battery to use as the trucks have different batteries in each of them?? Good site for info I must add.

    Reply  •  May 21, 2014 at 9:58 am
    • BatteryStuff Tech
      Randy, using an isolator will get better results. Thanks

      Reply  •  May 21, 2014 at 12:37 pm
  • Jim Bigger
    But why are there no tech replies in 2014?

    Reply  •  Rated article 5  •  May 12, 2014 at 2:49 am
    • Jeremy
      Technical questions can be submitted using the “contact us” tab at the top of the website. The comments for articles are not always reviewed by Techs, so the best way to get an expedient answer to a question, is to contact the correct department directly. Thanks

      Reply  •  May 12, 2014 at 12:00 pm
  • Frank Tucker
    I have n ABM 12volts, 120AH battery and a Wet Cell 12volts ,120AH battery can I connect both of them to my solar system in parallel

    Reply  •  May 2, 2014 at 11:36 pm
    • Jeremy
      We only recommend connecting batteries of same type, size, and age together in a system.

      Reply  •  May 12, 2014 at 11:58 am
  • Sam
    With a BS in Chemical Technology and eperience with batteries, I congratulate you for this article where expertise and general public understanding are mixed in a state of the art level. Talking for shalow cycle batteries where Ah has no sense because CCA matters people has to be aware that this battery has to be fully charged, and if discharges only 20% i.e below 12.6 V affects the life of the car battery. The status of battery has to be checked every weak, while you check the cold inflation pressure of the tire. To have a optimal inflated tire, means an optimal tire foot print i.e an optimal tire grip. So at this time check the battery voltage in your car parked overnight, start engine check again and you’l get 13.5 to 14.5 i.e. this is the status of alternator and voltage regulator in your car. If not using a vehicle use a battery tender that start charging at 12.6 V and stops at 14.2 – 14.5 V. Not hapy with comercial battery tenders, I made my own using a NE555 timer as precission comparator an more component. I can adjust ON at 12.6 – 12.7V and of at 14.2 to 14.5 volts according to the status (age ) of the battery. Increasing the battery voltage above 13.2 V, starts equilizing process. The weak cealls continue to charge and the strong start boiling. I do this proces at 250mA untill battery saturated, and after turns OFf to let battery to relax. I never buy a maintenance free battery, because I must check the electrolyte, level, top with H2O, and if necessary check the density.

    Reply  •  Rated article 5  •  April 29, 2014 at 5:58 am
  • Marie
    Sir Good day! i need with my newly bought gel battery, i dont know if i have to add sulfuric acid… i used it with my u.p.s. and it cant five any power to my computer when i unplug the power cable of the u.p.s.when i read the power rating 12.5V i dont know the ampere since i dont have amp meter. but in the battery it says 7Ah/10H. i thought it is better than my old VRLA with 12V 4.5Ah rating

    Reply  •  Rated article 3  •  April 5, 2014 at 8:50 pm
    • Jeremy
      Sounds like you should talk to the manufacturer. If its gell, then you wouldn’t add any acid, and most cases if its AGM it would come prefilled. The 7AH will last longer than the older 4.5AH one.

      Reply  •  May 12, 2014 at 12:22 pm
  • Dave M
    Can you use a AGM battery by laying it on it’s side or must it be in the upright position? If so, does it make any difference what side it lies on (battery posts toward the top vs toward the bottom)

    Reply  •  April 5, 2014 at 7:34 pm
    • Jeremy
      Dave, you can use an AGM in any position, except directly upside down.

      Reply  •  May 12, 2014 at 12:21 pm
  • Anders D
    Best written, most through article I have read regarding batteries, thank you!

    I have a BMW with AGM battery that was just replaced. I purchased a CTEK multi us 4.3 smart charger to lengthen the life of this new battery. I attempted to charge 3 days after installation, but became concerned as the charger was hot to the touch after 2 hours and still in the bulk charging state. Should I be concerned by the heat? There was no indication of anything awry other than the charger itself being hot.

    Interestingly, the old battery never remained in the bulk charging state this long and I never experienced the charger ever being warm.

    Reply  •  March 18, 2014 at 9:02 am
    • Jeremy
      I would not be concerned if it is hot after 2 hours, but if it has not entered into maintenance mode after 12 hours, I would check the battery to ensure it is good.

      Reply  •  May 12, 2014 at 11:56 am
  • Athar
    During periodic check when I observe that water level is low, I add distilled water to cells of lead acid battery. After a short time the fluid starts oozing out from the caps. It continues for about 12 -15 hours. What is the cause of this problem and how it can be rectified?

    Reply  •  March 17, 2014 at 5:15 am
  • Feterom Adolfo
    What are the electrodes and the electrolyte of an AGM battery????

    Reply  •  March 10, 2014 at 3:19 am
  • Harold
    Thanks for a very informative article. I own an older Honda Goldwing with lots of electrical gizmos. I have replaced the battery twice in last year. My dealer replaced the last under warranty about three months ago. The new battery worked fine when I was driving the bike frequently. But after letting the bike set for about two weeks I now have another dead battery. I hooked up my trickle charger, it only has a light that tells me it is charging, I left in on for about a week it did not recharge. I then hooked up my battery charger, it tells me it the battery is fully charged at 6 volts. Does this mean I have three bad cells? This is the second time this has happened, the first new battery lasted about six months this one about three. Do you think I got bad batteries. One I think maybe, but two in a row.

    Reply  •  January 19, 2014 at 6:03 am
  • Larry
    What a well written article. Thank you!

    My interest in the topic comes from wanting to maintain our trailer’s 12v AGM battery over the winter. We brought it home and put it in the basement workshop, but I discovered tonight that it was down to 10 volts.

    I’d like to put it in the cold room where there’s an unused plug but was worried about the “well ventilated area” instructions. The article says AGM batteries are the safest type, so would it be safe to charge it in the cold room? (10 × 4 × 7 feet, with top and bottom 4” pipe vents)

    Reply  •  Rated article 5  •  December 2, 2013 at 5:31 pm
  • John
    Brilliant article. Has really explained the internal working of various makes of batteries, better than anything I have come across here in the U.K.

    Reply  •  Rated article 5  •  September 1, 2013 at 3:04 pm
  • Pulkit
    I have 2 12 Volt batteries and want to use them both/ But i still want to use them for 12 volts. I just want extra backup.
    Please reply me anyone ASAP.

    Reply  •  Rated article 4  •  June 25, 2013 at 10:39 pm
    • Robin Brokaw
      Here is an article that explains the answer to your question. Should you have any further questions please feel free to email our tech guys at

      Reply  •  June 26, 2013 at 9:04 am
  • Sandie
    I am battery deficient. I am charging a battery on trickle charge, I know that much, but how do I know what the red and black bits on the charger mean? And how long til it charges? My hubby used to do all this but alas he is no longer here.
    Thanks for input

    Reply  •  May 9, 2013 at 4:35 pm
    • Jeremy Fear
      I appologize, but I‘m not quite sure what you are reffering to by the ‘red and black bits’. If you want to send me a photograph of the charger in question, my email is, then I will be more than happy to assist you from there.

      Reply  •  May 20, 2013 at 8:01 am
  • Donna
    I need a battery for a lighting setup for artfair booth (outdoors).
    I want to use 6 LED lights (14-watt Par30 bulb 3500K).
    also use of a fan for cooling the booth.
    which type of battery do you recommend.

    Reply  •  April 30, 2013 at 5:55 am
    • Jeremy Fear
      I would recommend an AGM battery for this type of useage.

      Reply  •  May 6, 2013 at 7:48 am
  • David
    Is it possible for a AGM battery to test 100% on a load test and still be bad? My battery shows 12.8v unconnected. In the motorcycle it shows 12.6v and with the key on it drops to 12.1 and won‘t start the bike.

    Reply  •  April 12, 2013 at 4:36 pm
    • Jeremy Fear
      Yes, it i s possible for it to have an internal ‘open’ in the cell. This happens when a weld point begins to come loose in the battery and it is unable to pass any significant current along the now thin connecting point.

      Reply  •  April 15, 2013 at 8:01 am
  • John
    I have a 12v 100 amp hour wet cell battery at work. It was taken out in the fall and put on a smart charger. Now I was going to reinstall it back into our equipment. I noticed that the end with the negative post is swollen. With a load test it passes at 9.5v‘s. no other physical damage is found on the case. Could the one cell have pressured up and not vented?

    Reply  •  March 19, 2013 at 9:50 am
    • Jeremy Fear
      It could have had some gassing at some point without actually damaging the cell, as may be indicated by the continued performance.

      Reply  •  March 19, 2013 at 3:45 pm
  • Sean
    Question, i have access to some lead acid batteries with much more life left in them…..more than i need at any one time. I want to put some in extremely long storage (5to10) yrs) Can i remove the electrolyte, flush then store? I read somewhere after flush to refill with ph neutral water and storing worked well. Another that after flushing used inert gas argon and sealed battery vents. Not concerned with losing a little capacity as these are very robust batterys. what would you recommend. I would charge these fully then remove electrlolyte and store it properly until redeployment.

    Reply  •  March 17, 2013 at 12:16 am
  • Tim
    Great Article. If I have a 80 Amp Hour battery and use a winch that is drawing 435 Amps under load with a 90 Amp alternator on the vehicle, how many minutes can I winch before I fully drain the battery or cause the vehicle to turn off? What formula are you using?

    Reply  •  Rated article 5  •  March 16, 2013 at 6:54 am
  • Donny
    Do you recommend a 2 battery solution for a boat? 1 for starting and 1 for deep cycle? Or would a dual purpose battery be sufficient? The engine is a 90 hp outboard.

    Reply  •  March 4, 2013 at 1:44 pm
    • BatteryStuff Tech
      We recommend using a dual battery setup versus the dual purpose batteries. You get better performance for your needs this way (starting the engine and running your electrical system).

      Reply  •  March 5, 2013 at 9:14 am
  • Jerry Anderson
    I have a Yamaha golf cart I purchased 4 yrs ago. Last winter I parked the cart in my heated garage and did not recharge the batteries during the 3 1/2 month period. By spring the batteries were so discharged thatmy cart charger would not work. I used a car battery charger to charge the 4 12V batteries separately. I limped through last summer having to charge to cart every 18 holes. I haave recently read about de sulfating the batteris. I was thinking about trying this before I spring for new batteries. Can you recommend a product to do this and if I can use the cart charger when doing this or would I have to charge the batteries individually. Thanks for the great article.

    Reply  •  February 17, 2013 at 9:50 am
    • BatteryStuff Tech
      I recommend using the liquid additive called BATTERY EQUALIZER and also the PP48L ON-BOARD DESULFATOR by Pulse Tech.

      Reply  •  February 18, 2013 at 8:58 am
  • Reg Rayner
    Sir, Thanks for the article. I Have a yacht with 4 Trojan T105‘s(6v – 2 in series- paralleled X 2) as one bank and a truck and tractor battery as the other bank. These are constantly charged by both solar panel and wind generator ( through a regulator) and also charged when the motor is running by alternator.
    My question;- Can I replace these wet cells with AGM batteries without changing any charging facilities? and if this is OK, do I replace them all with dual purpose AGM‘s or do I have 2 different banks, 1 starting , 1 deep cycle. I have a manual(idiot) switch, for selecting each battery bank or both. My motor is a Ford Lees 85 HP deisel. Thanks in advance.

    Reply  •  Rated article 5  •  February 12, 2013 at 8:59 pm
    • BatteryStuff Tech
      Most AGM batteries require no special charging accommodations. I recommend using deep cycle and starting batteries for their respective purpose. That way, you‘re getting the best performance based on the demand.

      Reply  •  February 13, 2013 at 8:49 am
  • Nicki
    my husbands 650cc motorcycle wasn‘t turning over so we figured it was the 12v battery. In order the check that it wasn‘t anything else we hooked up my new smaller scooter 12v battery to his bike and got it running. Now the scooter battery won‘t even turn the lights on the scooter even though the voltage meter says its fully charged. Could we have damaged the battery by using it in a different machine? The bikes take different size batteries with different amps but both 12 volts.


    Reply  •  Rated article 4  •  February 2, 2013 at 7:17 pm
    • BatteryStuff Tech
      There should be no issue using a smaller 12 volt starting battery for the motorcycle. I‘m surprised if the bike was able to start with a smaller battery. If the battery is truly fully charged, can you provide a resting voltage reading (bike off)?

      Reply  •  February 4, 2013 at 1:18 pm
  • Mizanur Rahaman
    Sir, I want to know a matter. When a 12V, 7.2AH rating battery is fully charged, is there any current flow to the battery where the charger is still plug in? and what is the actual voltage when the battery is fully charged? Please ans. to me.
    Thanks in advance.

    Reply  •  Rated article 5  •  January 25, 2013 at 11:17 am
    • BatteryStuff Tech
      Whether or not current is going into the battery after being fully charges is entirely dependant on the model charger you use and therefore I cannot answer your question. Micro processor controlled chargers will ‘float’ a battery after full charge. This is usually ~13.4 volts with little to no current. However, if you want to know what resting voltage (off charger) on the battery itself is considered full charge, please refer to this article for the answer.

      Reply  •  January 25, 2013 at 1:06 pm
  • Ms. Safety
    span class="caps">THANK YOU!!!! The information on this page was GREAT!!! It is now my “Go-To” reference for batteries!!!!

    Reply  •  Rated article 5  •  January 18, 2013 at 12:05 pm
    • BatteryStuff Tech
      Thanks for the compliment! :)

      Reply  •  January 18, 2013 at 12:06 pm
  • Silas
    Sir I will be very thankful if you guide me to build a charger of a 4 volt Li ion battery(which I have dismantled from my old laptop battery)……Thank You.

    Reply  •  Rated article 5  •  January 17, 2013 at 8:42 am
    • BatteryStuff Tech
      We are unable to provide you the information you need. We are a reseller. We do not build or manufacture any chargers.

      Reply  •  January 17, 2013 at 9:14 am
  • Adda Lamon
    I found the article SUPER helpful, because the guys at the auto parts store we talked with did a few confusing things. One guy called a battery looking like a 6-pack of soda cans a gel battery, where as the guy he called in for more info called it AGM, which it probably actually is. However, the guy who actually did know it was an AGM battery told us specifically that it wouldn‘t have any problems if it was completely discharged…which sounded quite attractive. We‘re still planning on purchasing the AGM batteries, but if I hadn‘t found the web page and wised up on the great info and tips you folks provided, we might have blithely followed his information and totally killed our battery (sucksville!). Thanks for a great website!!!!!!!!

    Reply  •  Rated article 5  •  January 16, 2013 at 8:41 am
  • Mike Smith
    Very Informative! (I assume 1 to be the highest rating). I have an ‘85 Ford class C motorhome with 2-12v batteries. Not sure if they‘re connected in series or parallel. It has a single alternator and a separate voltage regulator. With the engine running, one battery reads 12.4v, the other reads 16v. I assume this means the alternator is trying to charge this battery more? I first thought the regulator was bad & replaced it. At that time, one battery was reading 16.4v & the other 16.2. I discovered I had bought the wrong regulator, so I bought a second one. It read 16v and 17v. I put the original regulator back in, leading to my assumption that one battery won‘t hold a charge and the alternator/regulator is trying “harder” to charge it. The batteries were in it when I bought it, but they‘re different brands & I have no way of telling when either was purchased. Would my assumption be correct, and should I replace the battery with the higher voltage reading (or both)? What started this was when I bought the rv, before driving home I turned on the headlights and one went out immediately. I turned them off & the seller turned them back on & the second headlight went out. I left it for him to fix. He replaced both headlights. The first time I used them the new ones went out together. I switched to high beam & after about 10 seconds they both went out. I knew something was wrong & suspected the regulator first.

    Reply  •  January 12, 2013 at 4:48 pm
    • BatteryStuff Tech
      They do make 16 volt batteries and alternators. They are commonly found in race cars. 16 volts is too high for a 12 volt system. You could be overcharging your batteries.

      Reply  •  January 14, 2013 at 10:36 am
  • Garry Mcdonald
    RE; Can anyone please help? Scooter battery problem, will not take a charge.
    It appears that there may not be anything wrong with my batteries. I was told that the batteries must be charged every month or two or sulfation would set in. But the batteries not excepting a charge after 4 months was concerning. With no answers I decided to drain the batteries of two scooters by running the motors with the throttle on full and turning the lights on. However after 5 hours of constant running the scooters meters were still showing full and the volts where at 48.7 and my volt meter was showing 48.6 volts. After 5 hour only dropped 2 volts while protection shutoff is 42 volt. The next day I charged the batteries and yes they took a good charge, 7 hours and still taking a charge when I left for the day (I have them on a 12 hour timer). These Chaowei deep cycle gel batteries must be very good with little self discharge to not except a charge for 4 months.

    Reply  •  January 6, 2013 at 2:43 pm
    • BatteryStuff Tech
      I‘m glad your batteries are fine now. But for the future, it‘s not necessary to discharge these batteries down. They are not like NiCD batteries, there is no ‘memory effect’ or need to cycle charges. Batteries that are fully charged for a 48v system should give you 51.2 volts or more.

      Reply  •  January 7, 2013 at 9:08 am
  • Louw Penni Ng
    Very informative article, thank you. I have a problem with my camper van, 24 volt system for the truck, 25 amp alternator, fridge in the house on the truck that draws current from the 2 × 12 volt in series truck batteries. When ignition is off, the fridge stop drawing current. However, the truck batteries constantly run flat during driving, all well while I drive (diesel truck), but next morning the truck batteries are almost flat. The camper van house has it‘s own 12 volt battery, charged from solar, it performs OK. Currently the 12 volt fridge element draws amps from the second 12 volt truck battery, this implies that the fridge uses the power from the battery, not directly from the alternator. Is it possible that the power outflow from the battery is more than the charge inflow into the battery?. How many Amps can a battery continuously take while charging?. I now think I must tap the 24 volt directly from the alternator, then put it through a rectifier to get 12 volt, and then onwards to the fridge. This will leave the truck batteries free to charge at will without being drained by the fridge. If the truck batteries can only charge at say 6 amps, while the fridge draws 10 amps, the current set up will always discharge and leave me with flat batteries. Am I correct in my reasoning?. Please advise asap, Many thanks, Louw

    Reply  •  January 5, 2013 at 1:18 pm
    • BatteryStuff Tech
      There is no limit to what a battery can or cannot accept. A battery cannot say ‘no’ to charge. However, there is a safe range, up to 25% of the battery capacity, should be the max amperage charge rate. For a 50 AH battery, that would be a max of 12.5 amps per hour. Alternators usually don‘t have problems with overcharging, because of the electronic control unit.

      It sounds to me like you have a 24 volt battery system, but a 12 volt alternator. It seems like the fridge only takes 12 volts to run. What part of your system actually draws from 24 volts?

      Reply  •  January 7, 2013 at 9:02 am
  • Ed
    i have 3 sb 12100-s 12 volt 10 amp batteries for my bike which were stolen how do i wire the new ones?

    Reply  •  Rated article 5  •  December 26, 2012 at 2:29 pm
    • BatteryStuff Tech
      Is your bike have a 12v or 36v electric motor?

      Reply  •  December 28, 2012 at 8:36 am
  • Ed
    i have 4 batteries ps 1272 fs 12 volt 7.2 amp batteries were stolen how can i wire theser my bike?

    Reply  •  Rated article 5  •  December 26, 2012 at 2:22 pm
    • BatteryStuff Tech
      Is your bike a 12v, 24v, or 48v electric motor?

      Reply  •  December 28, 2012 at 8:32 am
  • Mike
    I use 4 – 12 volt dcm0035 interstate batteries hooked up to 48 volt configuration to power my pedicab. I have 2 sets-8 batteries total. They have had 11 months of being drained to approx 12 volts on the meter 3+ times a week. I use 2 noco gen 4 chargers. Mostly in the 10 amp mode….but sometimes doubled up on one battery set. Weather conditions from 35 – 110 F. How can I determine how much life is left? Besides the obvious based on how long they run before being drained. It seems they are at about 50% of new. Also…does my charger do a real 100% charge

    Reply  •  December 17, 2012 at 7:34 pm
    • BatteryStuff Tech
      There is no magical formula to predict the length of life remaining in a battery. Yes, the Gen 4 charger should bring the batteries to full charge before entering the gentle float mode on/off cycle. 12.0v on the meter is more than 50% discharge, which is more than we recommend for optimal performance.

      Reply  •  December 18, 2012 at 9:02 am
  • Andy
    I purchased a used boat in 2009, it has 2 identical West Marine starter batteries 650 CCA with a Perko 3 way switch, 1, 2 both or off). I‘ve never charged these batteries other than while running my boat, which is probably less than 50 hours per year. The engine is a 175HP Suzuki, with a 44 amp alternator. I feel like I‘m running on borrowed time and want to replace these batteries with AGMs. Should I go with 2 starter type batteries or 1 starter and 1 house? While boat is running is the alt charging both battery at the same time or does it follow the path of the Perko switch? Thanks, great site.

    Reply  •  December 16, 2012 at 2:09 pm
    • BatteryStuff Tech
      Since the batteries will be connected together via switch, I recommend using two of the same battery types and sizes. Therefore, if the batteries are used to start the engine I recommend two starting batteries. I recommend a deep cycle battery if you need 12v power while the engine is off.

      Reply  •  December 17, 2012 at 10:19 am
  • Nand
    Is it possible a Low maintanance Lead Acid can charge and discharge Simultanously ?

    Reply  •  December 4, 2012 at 1:36 am
    • BatteryStuff Tech
      No. If you are charging a battery and then you use it at the same time, the charger will attempt to supply the load. Depending what the load amount is, and if the charger can supply it, the battery may be charged at a lower rate or not at all and start discharging instead.

      Reply  •  December 4, 2012 at 8:08 am
  • Murugan
    I am using a 17 inch CRT monitor which consumes 80W power. Here in India we use 220V Ac for our appliances.

    Reply  •  Rated article 5  •  November 20, 2012 at 1:51 am
  • Murugan
    i bought a 12Volt battery 22months back with inverter for my desktop computer only. It reads GT-2100 C20 210AH. It‘s a lead acid battery. The dealer told me that i can use it for 10 and half hours for to power my computer only. from internet i came to know that one should not fully discharge a battery. i till date only once i used it up to 9 1/2 hours. never seen ‘battery low’ blinking any time till date. I always carefully kept the water level full by regularly checking the level indicators. On an average i use the battery up to 7 to 9 hrs these days because of big power cuts here and see it charged fully immediately when power comes. One problem is that if i use the battery for 9 hours then there has to be continuous power supply for at least up to 8 hours(+minutes) to get fully recharged. but here they are supplying power only on alternate hours. i.e, one hour power supply – one hour power cut – one hour power supply. and that too during the night only. during day time only for four hours power in given- morning 8to10 and evening 4to6. rest all day power cut. only in the past 3 months power supply became like this. i have been forced to use my battery very carefully and judiciously. My questions is will it affect my battery life by leaving it to be charged in alternate hours?.(i don‘t use it during night while being charged). i am really worried. we have abundant sunshine here. so i am willing to explore the possibilities to charge it using a solar panel. i want to know the maximum wattage or voltage should i supply to charge it in the minimum amount of time possible. tell me this much wattage up to this much hour. here we have 10~ hours of bright sunshine. please help.

    Reply  •  Rated article 5  •  November 19, 2012 at 11:09 pm
    • BatteryStuff Tech
      It‘s okay if the battery is receiving charge during irregular intervals. It‘s not the best situation, but it‘s not going to destroy the battery immediately. The truth is, the battery is going to build sulfation when its in a discharged state. Re-charging it will reverse this. That‘s good practice, but I understand if your situation prevents you from doing that in the best way possible.

      If you‘re looking for solar charging, the largest panel I recommend you can use to safely recharge the battery in the quickest time is a 900 Watt solar panel. This will charge at a rate of 73 amps per hour (35% of battery capacity). Less is fine, but no more for safe re-charging.

      Reply  •  November 20, 2012 at 11:58 am
      • Murugan
        thank you very much indeed. Have a nice day back there.

        Reply  •  Rated article 5  •  November 20, 2012 at 9:02 pm
  • Fawad
    My AGM 100amps battery for UPS is acting strange it gains full charge with 30-50 mins while it also discharges with 30-40 mins, my UPS is charging the battery on 10-12 amps. Any Help

    Reply  •  Rated article 2  •  November 19, 2012 at 12:09 am
    • BatteryStuff Tech
      What is the amount of draw (load) on the battery when its in use?

      Reply  •  November 19, 2012 at 2:42 pm
      • Fawad
        I don know exactly but its has a Samsung 42” Plasma Tv and and small Satellite receiver, that‘s all. And with the same load it gave me a Backup time of almost 2 to three hours.

        Reply  •  November 20, 2012 at 3:25 am
        • BatteryStuff Tech
          If I understand you correctly, your battery isn‘t lasting as long as it used to, and it charges quickly, too? Short charge/discharge periods? Sounds like the battery has sulfate crystal buildup on the plates. Sulfation causes batteries to age quickly. Refer to our other technical articles about how to remove sulfation.

          Reply  •  November 20, 2012 at 4:29 pm
  • Greg
    ”… An amp hour (AH) is a rating usually found on deep cycle batteries. The standard rating is an Amp rating taken for 20 Hours. What this means, say for a 100 AH rated battery is this: Draw from the battery for 20 hours and it will provide a total of 100 amps …”

    Should say …
    ”… and it will provide a total of 100 amp-hours …”

    Reply  •  October 28, 2012 at 6:22 pm
    • BatteryStuff Tech
      Thank you for the suggestion. We will make the change.

      Reply  •  October 29, 2012 at 9:21 am
  • David Cuneo
    Thank you for your article, I have a question. I bought a 2 month old (STICKER ON IT) battery from junkyard, outside cell was punctured in a crash, looked inside all electrolyte was gone from the one cell. I repaired the plastic casing,it could now hold liquid safely. Could i add electrolite from an old battery or would that have too many sulfites , it would be better to get a motorcycles worth at autozone? I am going to turn in my old battery anyway as it is a core charge… What do you think?

    Reply  •  Rated article 5  •  October 26, 2012 at 12:36 am
    • BatteryStuff Tech
      The moment oxygen hits activated plates in a cell, sulfation will form rapidly. My opinion is that it's not worth the effort or the risk. I recommend buying a new battery. Even if you were able to restore this one a bit, I doubt it will last very long and it would not be safe as the internal resistance when charging will be greater than a healthy battery, which you will risk the battery overheating as a result.

      Reply  •  October 26, 2012 at 8:33 am
  • Wilfred Kube
    I have a Toyota Coaster bus which is fitted out as a motor-home. The vehicle was manufactured with a 24 volt electrical system, which uses two batteries in series, of 12 volts each. I have outlined a description of the auxiliary electrical system below, but my basic question is, how can I know how depleted my auxiliary batteries are at the end of a day in which the refrigerator has been working for a long time?
    I think the basic rule is that the batteries should not be discharged below 50% of their capacity, but what reliable method can I use to determine when they have reached this point? There are two auxiliary 12 volt batteries in series, each 120 amp-hour, to provide power for the “house system” – namely refrigerator, lights, water-pump, and various 12 volt power outlets. The refrigerator is the major user of battery power, because it is a compressor fridge which uses the equivalent of 12 volts 8amps (i.e.96 watts) while it is running, and it runs for approximately 8 to 12 hours in each 24 hour period depending on how hot the weather is. The auxiliary batteries are charged by two solar panels of 80 watts each, and receive additional charging from the vehicle alternator when the engine is running. There is a battery isolator which automatically disconnects the auxiliary batteries from the vehicle electrical system when the engine is not running. The voltage regulator for the solar panel charging system provides a constant display for the auxiliary system, including the auxiliary battery voltage. I have been in the habit of checking the voltage last thing at night, and first thing in the morning, to find how much power the fridge has taken from the batteries. If the night time voltage is below 24.8volts, then the morning reading is below 24.0 volts. The problem is that if we have not done much driving on a particular day, and the solar panels have not done much charging because of cloudy weather, the night-time voltage may only be 24.2 volts, and the morning voltage not much above 23 volts. If the battery is at 24.2 volts when the fridge is not running, then when the fridge starts running the voltage reading drops down to about 23.5 volts. And so my question remains, what is the lowest acceptable voltage for my auxiliary battery system, so that the batteries are not damaged by being discharged too much. Thank you for reading through a long and detailed letter, but I wanted to provide sufficient background information.

    Reply  •  October 22, 2012 at 4:35 pm
    • BatteryStuff Tech
      Resting voltage of 24.4 volts is 50%. When you reach this point, stop using the batteries until you can recharge them again.

      Reply  •  October 23, 2012 at 10:50 am
      • Wilfred Kube
        Thank you very much for your helpful site,and for your prompt reply to my query.

        Reply  •  October 24, 2012 at 2:13 pm
        • Yves Van Damme
          I do have the same system as Wilfred, although I use a Tripp Lite to invert current from 12V to 110V (2,400 Watts)
          I have always used 3 cheap regular truck size batteries, charged by the alternator and, with the almost every WE driving, had no problem running everything for 3 years without having to charge the batteries with an external charger
          Recently, to lower the weight, I bought 2 trojan deep cycle batteries 225 that almost totalled the same Amp as the 3 previous ones
          To my surprise, these batteries have gone dead last week after 6 months of use, although well maintained as far as water and regular charging through the alternator
          The Tripp Lite works fine and we always avoid to use the battery lower than the yellow and red lights which indicate a battery load of 50 %
          We did have a 2 minutes run on red light 2 weeks ago (as much as 80% discharge) and to prevent any further problem I recharged the batteries with an external charger together for 20 hours (for the first time in the last 10 years); the charger indicated 14V at the end of the charging process.
          Unfortunately, on a trip last week I lost power faster then ever and ended up having to only use the refrigerator while driving, forgetting about the water pump or the coffee maker; I tried to recharge the batteries since then but the charger wont go over 10 volts and goes down to 8 and 7 after 10 hours
          My question: since these trojan batteries are very expensive where I live (Peru) should I invest in a charger, what kind, and should I charge the batteries everyday from my house? The car is in the street and I cant go check every 2 hours what the voltage is, so is there a charging process that is safe, guaranteed on the long term for these batteries?
          Once again this is the full description of my configuration:
          bus sprinter with alternator of 100 Amp
          starter battery of 120 Amp
          2 trojan deep cycle 225 130 amp each output 12V
          one tripp lite inverter 12-120V 2,400 Watts
          Thank you so much for your answer which should interest many people like me who just want to understand how to run a simple 3 or 4 devices in their camper

          Reply  •  February 9, 2013 at 1:22 pm
          • BatteryStuff Tech
            It sounds to me like your current charger is probably fine but the batteries may be defective or had their life significantly reduced when they were overly discharged those 2 weeks ago.

            Reply  •  February 11, 2013 at 11:13 am
  • Peter
    Thank you for your great work! I have learned a lot.
    I have a Die Hard 1150: 20ah AGM power pack. As per your explanations, I leave it plugged in because it has an integrated smart charger that is supposed to provide a safe float charge to maintain the battery‘s health. I have two questions relative to this:

    1. Is it normal that the battery is slightly warm to the touch when it is plugged, has reached 100% and is receiving a maintenance charge?

    2. Are dangerous gases given off while the battery is plugged in and receiving a trickle charge? My battery is plugged in in the basement workshop in a fairly large house.

    Thanks for any information you can provide and take care.


    Reply  •  Rated article 5  •  October 14, 2012 at 3:22 pm
    • BatteryStuff Tech
      If the battery is warm, it‘s because there is more resistance in the battery internally than normal. There is probably a good amount of sulfate crystals on the plates in the cells, which would cause the charger to work harder to maintain the float mode. Sulfation robs the battery of power, but can be reserved with de-sulfation units and chargers.

      Gassing should not be an issue if the battery is healthy. Only significant over-charging should cause an AGM to vent excessively.

      Reply  •  October 15, 2012 at 1:14 pm
  • Matt
    Great article. I learned more than I‘ve ever known about batteries, but I still don‘t know much.

    I am wondering, I recently purchased a year round ice fishing house / camper. I‘m looking at batteries now and am leaning towards an AGM. Is that what you would recommend? Again, this battery will be used year round. Freezing cold when it sits for 4-5 days at a time without being used, then it will be used on the weekends when I go fishing. Then during the summer it will be used in the heat.

    I‘ve also seen a couple mentions of solar chargers. I do have a generator that i plan to use to recharge the battery when necessary, but am wondering if it would make sense to leave a solar charger hooked up to the battery constantly. The location of the battery in the house would make it very simple to hook a solar charger up and have it mounted either directly in the window, or just outside attached to the side of the camper/fish house. Then even when in use, the battery would be charging, right?

    Thanks in advance for any response.

    Reply  •  Rated article 5  •  October 9, 2012 at 4:31 pm
    • BatteryStuff Tech
      For extreme temperatures, the Gel batteries are the best. They also have the slowest discharge rate. Having a solar panel is a great idea, and perfectly safe even if a generator is on or you are using the batteries, if you are also using a solar controller (which regulate safe charge voltage levels, and prevents back feed into the panel). But yes, if a solar panel is receiving sunlight, the battery will also be charging as well.

      Reply  •  October 11, 2012 at 9:28 am
      • Tim
        Great Article !

        For what it‘s worth. I use NorthStar pure lead AGM batteries. They have the widest operating temperature range (-40 deg F to + 149 deg F) and have a two year shelf life. Never saw a gel battery with that type of operating temperatures. I have one in in my truck. Never a minutes worth of problem.

        Reply  •  Rated article 5  •  January 15, 2013 at 12:10 pm
        • BatteryStuff Tech
          Pure lead vs recycled lead does make a difference in performance. NorthStar batteries sounds like good batteries.

          Reply  •  January 15, 2013 at 1:19 pm
  • Adam Johnson
    Thank you for your opinion….I would like to use an electric golf cart for in-town transportation in a small town in the San Juan Mountains of Colorado, year around. I am a teacher and typically only drive it back and forth once or twice a day, about one mile each way. 1st question: It can be very cold here on winter mornings, (-20 degrees and more),but then warm-up to 30 degrees on the same day, is there a battery that can handle the temperature range, and still have a reasonable life length? 2nd question: I have a solar panel that I could place on the roof, get a charge controller, and have the batteries always trickle charging, how will that effect the battery life? I have a 36 volt charger that came with the cart. The cart is perhaps 20 years old. The batteries it came with were all exhausted, I took them to a recycler. I was thinking of spending the 150.00 each ( including core fee) for 6 batteries, and stop driving my gas vehicle. I‘d appreciate some advice.

    Reply  •  September 27, 2012 at 7:00 am
    • BatteryStuff Tech
      For the greatest range of operating temperature, the gel batteries would work the best. For a solar panel, you would either need a single 36 volt panel, or 3 12 volt panels in series. That‘s a good idea if you want to see the longest lifespan from the batteries. The charge controller, make sure it‘s safe for gel batteries, which require a slightly lower voltage charge than most other batteries need. We sell Trojan T-105 6 volt batteries for $139 each. No core needed.

      Reply  •  September 27, 2012 at 8:17 am
  • Ameya Pawar
    I want to increase the voltage of 2 batteries from 24V to 180V. Is it possible?

    Reply  •  Rated article 5  •  September 26, 2012 at 4:55 am
    • BatteryStuff Tech
      There are some step up converters to increase voltages, but we do not sell them. Additionally, I think it may be hard to find one that will step up to 180 volts.

      Reply  •  September 26, 2012 at 9:26 am
  • Selvan Albert
    Hi all,

    Current setup:
    1) Two UPSs. Both are independent systems.
    2) Both are identical; Manufacturer: Delta; Model:J-Series 7 KVA. Each capacity: 5000 Watt, 230 Volt AC.
    3) Each has 20 numbers of 12 Volt 26 AH batteries connected in series for a 240 Volt DC, 26 AH battery bank.

    a)Design a battery bank in such a way that even if one battery fails, the bank would still be operational and keep the UPS running until the failed battery is replaced.
    b)Try reconfiguring existing battery bank so that cost is minimized.

    Proposed setup:
    1)Instead of two identical but separate battery banks as configured now, reconfigure the 40 batteries in one battery bank.
    2)Batteries will be connected in series and also in parallel as listed in the diagram.
    3)Two batteries will be connected in parallel to form one 12 Volt 52 AH parallel battery bank pair. Twenty such pairs will be linked in series to form one 240 Volt DC 52 AH bank.
    4)Connect both UPSs to this one battery bank.
    5)The 230 Volt AC “Output” of the UPSs would remain independent as they are now.

    Attached Diagram:
    Both the current setup as well as the proposed setup are illustrated.
    (No change in the independent “Outputs” of the two UPSs. The 230 Volt AC “Output” of the two UPSs would remain the same (as independent outputs) in the proposed setup as they are now in the existing setup.)

    1)When any one battery fails, the entire bank would still be operational. (Hence, the UPSs will not fail.)
    2)So long as “both” batteries connected in any parallel pair do not fail, the bank would still be operational.

    1)Would the battery charging circuits in each UPS somehow interfere with each other?
    2)Are there other issues and/or disadvantages in the proposed system that are overlooked?
    When electrical power is On, would the battery charging systems in each UPS interfere with each other when charging the single battery bank? In other words, currently just as one UPS charges its own battery bank, would the two UPSs charge the single common battery bank without issues?

    We would be very thankful to you if you can please give us your valuable feedback on our proposed battery bank set up.

    Selvan Albert.

    Reply  •  Rated article 5  •  September 19, 2012 at 7:26 am
  • Mark
    it helped me alot but google‘s better

    Reply  •  Rated article 4  •  September 17, 2012 at 11:44 am
    • BatteryStuff Tech
      What did you find that more helpful? Lease share it with us.

      Reply  •  September 17, 2012 at 12:18 pm
  • Austin
    this rlly helped me in my auto electrical class

    Reply  •  September 17, 2012 at 11:41 am
  • Bo
    Hi James, thank you for the information and excellent explanations! How can I figure out what type of battery in my car (2007 BMW X3)? The battery is a sealed maintenance free battery. It’s the original battery. The part number is S: 61 21 8 385 398, and the label says it’s 90 AH and 720 CCA, but no manufacture name on it though. I called couple of BMW dealers, but they didn’t know. Hopefully you can help me out. Thanks in advance!

    Reply  •  September 11, 2012 at 1:53 pm
    • BatteryStuff Tech
      Sounds like an AGM or a VRLA battery. Both are different types of lead acid batteries, the sealed ones as apposed to the conventional flooded type. It‘s not going to be a gel, I can almost guarantee that. Gel batteries are completely sealed. If there any ventilation or even vent slits on the top of the case, then it‘s not a gel. That‘s good too, because gel batteries don‘t make good starting batteries. They‘re fragile.

      Reply  •  September 11, 2012 at 2:20 pm
      • Bo
        Thank you very much for your answer. I have a battery charger, and I need to choose one of Standard, AGM, and GEL battery type. Which type should I select?

        Reply  •  September 12, 2012 at 6:42 am
        • BatteryStuff Tech
          Gel is the safest, because it uses the lowest charging voltage of the three. If you are not sure, the gel setting is always a safe option. Otherwise, if you think it‘s an AGM (check to make sure there are ventilation slots to confirm it‘s not a gel) then use the AGM setting.

          Reply  •  September 12, 2012 at 7:45 am
  • Charles Wehland
    I have an electric 2-wheel scooter that my wife uses. It has 3-batteries linked together. How do I hook-up the cables on my battery charger to charge this bank of 3-batteries?

    Reply  •  September 8, 2012 at 1:34 pm
    • BatteryStuff Tech
      It depends entirely if the batteries are suppose to be in series or parallel. The answer to this question depends if the scooter runs off 12 volts, or 36 volts. But the surest place to connect your charger to are the same terminals that the scooter‘s motor is connected to in order to run.

      Reply  •  September 10, 2012 at 8:57 am
  • Bob
    When using a deep cycle battery in a Solar system, using DC 12 volt lights. Is there a way to automatically shut off the lights before it discharges the battery too far?

    Reply  •  September 7, 2012 at 11:38 pm
    • BatteryStuff Tech
      Yes, you would need a battery disconnect or a power switch. Priority Start and Battery Guard are two brands that will do this automatically. We sell these in our battery accessories category.

      Reply  •  September 10, 2012 at 8:42 am
  • John Fetter
    This is a philosophical comment. Lead-acid batteries suffer from self discharge. Batteries actually spend overwhelmingly most of the time not on charge but doing absolutely nothing at all. This is what causes sulfation. So what do the experts recommend battery users do? Treat the sulfation. A hundred year old cure! How about treating the battery with something that stops the self discharge?

    Reply  •  Rated article 5  •  September 6, 2012 at 12:52 am
    • BatteryStuff Tech
      Keeping a battery on a trickle charger will prevent self discharge. Beyond that, asking a battery not to self discharge is like asking a person not to age. It‘s a chemical issue, and healthy batteries will self discharge at a lower rate than older batterie or cheap batteries made from lesser quality materials.

      Reply  •  September 6, 2012 at 8:48 am
  • Will Helbich
    I have new replacement 4 × 12v 18 ah deep cycle agm batteries wired in series for an e-bike, the 48 v charger charges the bank at around 54-55 v, Now,the original batteries performed the last 2 years as expected for 300- 400 cycles with good range , but these new replacement batteries are failing within weeks, less than 30% range than originals. When testing the charging voltage going to each individual battery in series , it varies from 14.1 V- 15.9 V from one battery to the next. and under a timed load test on each charged battery, they range from 2 min to 55 min before dropping below 11.5 /cell. Are the batteries poorly constructed or is it a charger issue? Thanks for any insight you can provide.

    Reply  •  August 31, 2012 at 3:38 pm
    • BatteryStuff Tech
      How much was the load amount for the test? 15.9 volts is on the high side as far as charging goes.

      Reply  •  September 4, 2012 at 3:10 pm
  • Jeff
    Hi, just got a new kirkland battery and it has the 6 cells under the cap. Not all of the cells have liquid in them to the top. is this normal for some cells to have more liquid than others, should they all be filled to the top? I could not see any fill lines as to where the level should be. thanks

    Reply  •  Rated article 5  •  August 27, 2012 at 5:01 pm
    • BatteryStuff Tech
      Yes, the cells should be balanced, even as far as liquid levels. Please only use distilled water. They do not need to be filled to the rim, but definitely the plates should never be exposed. If this happens, the plates react with the oxygen in the air and form sulfation rapidly. I hope this answers your question.

      Reply  •  August 28, 2012 at 10:24 am
  • Qusay
    hello i have 8 deep cycle battery 12v 200Ah connected series/parallel to supply a ups system and it charged by acostant charger 52.5 V 35A its working abot 18 month every day about 6hr on the UPS and now begin loose its capacity when i check the voltage for each battery while the charger working some of them give 13,4v and other 12.66 and 12.9 so it the sulfated or need for reacharging with a smart charger .


    Reply  •  Rated article 4  •  August 19, 2012 at 6:52 pm
    • BatteryStuff Tech
      I don‘t know what the load is, but for a 48 volt system the charger seems a little too low if it‘s charging at 52.5 V. It should be 56 V or so under the bulk charge mode. For float, 52.5 is okay. I‘m not sure what your question is about.

      If the batteries are individually reading different voltages, that‘s not good for the system. Are the batteries the same age? 13.4 v is a little high but good full charge, while 12.9 v sounds just about right. 12.66 v could use more charge. If it‘s not able to reach any higher voltage, sulfation is a good cause of that. An onboard de-sulfator like the Power Pulse or ODB from Battery MINDer would be recommended to fix that battery. No need to disconnect it from the others or change your system.

      Reply  •  August 20, 2012 at 11:47 am
      • Qusay
        thanks alot for your assistant
        1- my battery have the same age
        2- i cant increase the charger voltage because its max volt is 52.5 also till now i dont try another charger or charge each battery individually
        3- these readings for each battery but while they connected to the charger and for example when im add all the reading ( 13.4+12.66+12.9+13.54) its equal to 52.5 which is the charger voltage and when im disconnect the charger and after 1 hr battery reading is ( 12.7 , 12.5 , 12.7 , 12.6 ) i think battery No 1 and 4 prevent the voltage to rais in battery 2 and 3 so they cannot charge fully , also at the first 8 month all the battery have the same reading when charging .

        do recommend individually charging for each battery to force it reach to 13.6 v and accept current , like using 48 v charger with 4 bank or its no problem to use 48 v charger with one bank also if i want to desulfate it it is better to use obd-12 for each on or use obd 48 for each 4 batteries

        also what is the recomended methode to charge and maintain this system to get maximum life for the batteries .
        thanks & best regard

        Reply  •  Rated article 5  •  August 20, 2012 at 2:35 pm
        • BatteryStuff Tech
          A 4 bank 48 volt charger would charge the batteries individually, which may solve the problem. 52.5 volts is good if the batteries are fully charged. But since they are not all charged, I recommend the charge rate should be higher for the two to charge up. If you use the OBD-12, you‘ll need one for each battery. Otherwise, you can use a single OBD-48 for all four batteries in series.

          Reply  •  August 21, 2012 at 7:50 am
          • Qusay
            thanks to helping me to solve the problem and thanks for the site which give this amount of data for users , really great site and great staff

            thanks again with my best regards

            Reply  •  August 21, 2012 at 11:01 am
  • Max Williams
    I have (8) x 6V x 125AH deep cycle batteries producing 24V in a series/parallel config
    charged by a 250W x 24V solar panel,powering a 24V fridge/freezer 24/7 drawing 2A when running.
    Am i correct in assuming my total stored AH capacity should be sufficient to run the fridge
    with minimal sunlight for a few weeks.

    Reply  •  August 16, 2012 at 2:52 am
    • Jeremy Fear
      As long as you rpanels recieve at least 5.5 hours of direct sunlight on the panel then you should be good. If you have any further technical questions, please email them to

      Reply  •  August 16, 2012 at 9:43 am
  • Bob
    i have a solar system & i am using a device that measures the voltage of the batteries and send it through a serial port to the computer, that can show me the health at anytime of the day.
    i have 8 batteries connected in parallel, and the problem that i am trying to think of a solution is that the measuring device is treating the 8 batteries as one, and gives me a single reading. But in order for my monitoring project to work, i want to be able to measure each battery alone, even when they are connected in parallel together…
    I know this sounds impossible, but I still need to think of all possibilities.
    Anyone with any clues would be very helpful.


    Reply  •  August 14, 2012 at 8:16 pm
    • Jeremy Fear
      Any technical questions can be emailed directly to for the fastest response.

      To answer, at least the best I can, I would personally hook up the tester that you are using to an 8 point switch, where each of the 8 modes were connected to one of the batteries directly. You could then switch the connection on the monitor to each battery individually, even though they are all hooked up together. The only real downside to this would be that if your device is one of the more accurate types, then it will be thrown off by resetting it on each battery and will cease to be as accurate. On the other hand, if it is not a super accurate one, then I wouldn‘t bother setting it up this way anyways. So while its not completely impossible, its a bit of a catch 22. The accurate one will cease to be so, and the not as accurate one falls in the ‘why bother’ catergory. Hope that helps! :)

      Reply  •  August 15, 2012 at 11:16 am
  • Bob
    Hi, First of all I want to say that your tutorials have been very useful for me and I have learned very much.

    I have an off grid house that I power with four 12V 245AH 8D AGM batteries wired in Parallel which are connected to a xantrex 3000W sine wave inverter/charger. I have a xantrex link pro battery monitor that has a programable alarm relay that I have set to start the generator when the batteries get down to 55% state of charge and to turn off again at 85%. occasionally I turn the generator on manually to bring the batteries up to 100% charge to synchronize the monitor. I just set the system up a few weeks ago and it is working very well so far. I am not there very often but whenever I check on it, the batteries are within range and the generator runs for 4 or 5 hours a week. The only thing running while I am gone is the refrigerator and a half dozen 7w led lights that I have come on after dark. I don‘t have any other source to charge the batteries yet (solar or wind).

    I have a couple of questions:

    Do you think this system will work well in terms of longevity? Is there something I should be doing differently, such as setting up the monitor to keep the batteries at a different state of charge (more or less discharge)? The reason I don‘t bring them to 100% every time is that the generator needs to run for quite a long time to get the extra 10-15% into the batteries and it seems like a waste of fuel.

    Second, if I had an always on wireless internet connection, do you know of a way that I could monitor the battery condition from far away via the internet? So that I would know if there was a problem with the generator not coming on. I don‘t know if there is a battery monitor available set up to do that. Any ideas you might have would be geatly appreciated.

    Thank you.

    Reply  •  August 11, 2012 at 7:17 pm
  • Bill
    I have an old (‘85) Honda ATV. After some reading (obviously not enough)I purchased a gel cell battery that was advertized as appropriate for my ATV. It did not take long for the battery to reach a point where it would light lights but not turn over the electric starter. After more reading, it would seem that the alternater would need some “adjusting” to keep this battery charged. I can find many references to external chargers, however I have, so far, been unable to find any information on what needs to be done to upgrade the charging system of the ATV for gel. Any help here?

    Reply  •  Rated article 5  •  August 3, 2012 at 2:01 pm
    • BatteryStuff Tech
      We do not sell anything that would regulate an alternator to a safe voltage for Gel batteries (no more than 14.2 volts). I imagine it would be costly. It‘s easier to simply purchase an AGM battery for the ATV and not have to worry about charging differences.

      Reply  •  August 3, 2012 at 4:07 pm
  • Cpt Crunch
    span class="caps">THANK YOU FOR SHARING YOUR KNOWLEDGE! WOW! I have been working with batteries for years, yet never really understood their differences, much less how to match them with various applications. Here I have been buying based on the highest amp/hr AND CCA, when I should be looking harder at one or the other. And now there‘s an AGM???

    Okay, ….a question:

    The GPS/Fish Finder on our boat uses around one-third of an amp. My typical day of ocean fishing is between 8 and 10 hours. I do not like it on the starting battery and am looking for options.

    The first question is AGM or a small gel cell? I am looking to understand the balance between them, in particularly, the lesser chance/lower cost of replacing it in the event I trash it, …which I am convinced is destiny – or the higher cost of a gel that I will not trash. (While I think I am very easy on batteries, evidence shows they do not seem to like me.) So, is it just math, or are there other considerations I should be looking at?

    If using an AGM, the YT4L-BS will give me 9 hours of GPS. Correct? Or should I be looking at double that size, like the YT6.5L 12v AGM? I just cannot see spending $140 for something a 41 battery will do just as well for.

    Prior to reading your pages, I had heard of AGMs, but the information was skewed. I was told they are just like gel cells, which I now know is only a half-truth. I can clearly see the differences over wet and gel, but I am most attracted to the low replacement cost if I, indeed, trash it.

    Which one do you recommend?

    Again, thank you for the site, …and I welcome your sagacity.

    Reply  •  July 30, 2012 at 12:42 am
    • BatteryStuff Tech
      AGM batteries can be recharged with any battery charger. Gels are more fragile, and they need a charger with a safe voltage profile for charging. Gel batteries can be discharged further without the damage it would cause an AGM. We recommend no more than 50% for AGM. The Gel can go as much as 80% discharged.

      For your GPS/Fish Finder, I recommend a deep cycle battery. The YT4L and YT6.5L are motorcycle starting batteries. I recommend a sealed lead acid deep cycle battery. Having one at least 9 AH in capacity should give you 10 hour of safe runtime given the 300 mAh draw.

      Reply  •  July 30, 2012 at 3:17 pm
  • Steve
    Thank you for your great information. It always helps to read it rather than using guess work!
    I do have a question for you that I hope you can help with please.
    I have had our motorhome for nearly 2 years and it came with a couple of solar panels – one of which is rather large. However we have had a couple of problems with cooked batteries! Basically, we discovered our battery was being cooked by one of our solar panels as the regulator was not working. We got that sorted and replaced the very smelly leisure battery. But just recently the same thing happened again and we discovered that our very large solar panel didn‘t have a regulator on it at all. We realised very quickly and disconnected the battery which was beginning to sulphar up and smell. We have since added a regulator and although the battery was able to be cleaned up we are finding that it now will take a decent charge but is only holding that charge for about 45 minutes. So we have 2 great solar panels and no holding charge. Do you think that this is due to the damaged battery or could it be something else? It is a sealed battery and so we cannot tell what state it is in internally. Thank you.

    Reply  •  Rated article 5  •  July 25, 2012 at 2:18 pm
    • BatteryStuff Tech
      If the issue was sulfation, then the solution would be to try to restore the battery with an on-board pulse de-sulfator. But if the batteries have been over-charged, and they drain very quickly, then there really is nothing else you can do. Overcharging can dramatically age a battery rapidly.

      Can you provide some voltage readings? Say, one at rest. While on the charger. And finally, a reading 45 minutes after off the charger. With these numbers, I can more accurately diagnose the battery.

      Reply  •  July 26, 2012 at 8:35 am
  • Roger
    A really helpful, first rate site. Thanks! My question relates to appropriate charging of an AGM (or alternatively, a Gel) battery on a vintage, generator equipped car. The generator and standard regulator setup are inadequate to operating the car with headlights AND, say, windshield wipers or heater blower. The set-point of the regulator has to be raised to 16 volts to avoid battery drain whilst driving, and so after starting, and within about 5 minutes, as the voltage reaches 16, I switch on the headlights to load the generator down to about 14.5 volts. After several hours drive, or when other loads are added, this voltage will fall below 14 volts. Is this procedure good enough to maximize the life of an AGM or Gel battery? An alternator conversion is being considered. Comparing say a Delco 10Si with a Mitsubishi that might be used for tractor or marine purposes, what should I be careful about? I am thinking of the different battery applications, tractor, marine, etc, versus the Delco regulator of 14.4 volts. Thanks.

    Reply  •  July 22, 2012 at 9:07 am
    • BatteryStuff Tech
      16 volts is too high and will damage a gel battery. 14.6 -14.8 volts for an AGM is just right. If you need to charge a gel battery, a regulator will be needed to keep the voltage from exceeding 14.2. An alternator would be a good idea. Regularly pumping 16 volts in a battery will cause the internal resistance in the battery to spike and heat up. It‘s not recommended for the long run.

      Reply  •  July 23, 2012 at 4:07 pm
  • Bill
    May I charge a 6v auto battery using a 12v (rated) solar panel?

    Reply  •  July 14, 2012 at 9:40 am
    • BatteryStuff Tech
      No. This will be like trying to run a gasoline car on diesel. You can either use a 6 volt panel for the car battery, or series the battery with another of identical specs to create 12 volts.

      Reply  •  July 16, 2012 at 10:09 am
  • Marissa
    I just bought a JL 50 scooter and the battery it came with is a12. Battery which came with the liquid which instructed me to put liquid into the cells and then cap it with the plastic cap plate that came with it and then charge fully before using. I filled it with the liquid two days ago but have not been able to go buy the charger which I Plan on buying at wall art tomorrow. Last night and one time today the battery cell cap has popped open on only one cell (the last one) loud enough for me to here it ( it is in the same room with me). I am worried something is wrong, should I be concerned? Is this normal ? Is it because I squeezed the bottles when adding the liquid?

    Reply  •  July 13, 2012 at 6:49 pm
    • BatteryStuff Tech
      Congratulations on the new scooter!

      Squeezing the battery would not be a problem. It usually takes hours for the acid to become fully absorbed. The only cause I can think of for the caps popping off is overheating. Is the battery in the garage? Did you install the vent tube that comes off the side?

      Something is causing the battery to build pressure, and it‘s not venting fast enough. If the liquid levels decrease, please add distilled water. But other than that, everything else should be fine. Venting is normal, but caps popping off is not. You definitely don‘t want that happening while on the road.

      Reply  •  July 16, 2012 at 10:00 am
  • Francisco

    Can I charge a wet lead acid battery SLI in paralel whit a AGM deep cycle whit only one alternator?
    A relay disconnect de paralel when the motor is off.


    Reply  •  July 10, 2012 at 11:37 am
    • BatteryStuff Tech
      For a situation like yours, I recommend using a battery isolator switch, which can be used on up to 120 amp alternators to conveniently allow for adding a spare battery in your car, boat, or RV. The unit is a fully automatic switch that allows the engine alternator to charge 2 batteries, while keeping them electrically isolated from each other. This will prevent current flow from one battery to another, thus allowing each battery to be an independent power source.

      You can see it here: /battery-products/switches/Bi303303.html

      Reply  •  July 10, 2012 at 12:17 pm
  • Trevor
    Shouldn‘t this battery be dead? Why is it working?
    I just bought a 12v 7.2ah Valve regulated Lead acid battery for $5.00 I tested the volts and it‘s at 12.75 a sticker reads “Top Charge Date 4/26/2007

    I ran a motor from it for 2 minutes and it held up. I charged it and it took a charge. Should I run a cordless drill motor from it for as long as I can to see how long it last? Or should I leave well enough a lone?
    Thanks Trevor

    Reply  •  July 8, 2012 at 2:12 pm
    • BatteryStuff Tech
      12.75 is good voltage. If the battery was kept maintained fully charged, there‘s no reason not to use it as long as there‘s nothing physically wrong with the battery. Draining it down with lights, drills, motors is good, you should measure the voltage under the load to see if it holds up and doesn‘t crash. When you‘re done testing it, it‘s good to recharge it ASAP and keep it charged when you‘re not using it.

      Reply  •  July 9, 2012 at 10:19 am
  • Kyle
    If you have a bunch of 12V deep cycle batteries paralleled (or groups of series 6‘s then paralleled to make 12V) – is it best to isolate each group so that at night the batteries are not fighting each other. I mean isolation as in commercial heavy duty battery isolators. Is this much more necessary if the bank is not typically receiving a daily charge top up (i.e. solar)?

    Reply  •  June 30, 2012 at 12:29 am
    • BatteryStuff Tech
      If the batteries in the bank are charging and discharging together, and they are of the same type, size, and age, then there is no need to disconnect them. They act together as a single batery unit. But if the batteries are unevenly charged and/or different capacity, they will try to equalize and balance. This is can harm a small battery if connected to a large battery, which is not recommended. Different age and type of the batteries can also cause inbalance.

      Reply  •  July 2, 2012 at 10:24 am
  • Marv
    can i use lead acid batterys in this hoveround to get it going to test it?

    Reply  •  June 26, 2012 at 7:20 am
    • BatteryStuff Tech
      7-8 volts is extremely discharged. The batteries are probably beyond repair due to sulfation. If they cannot reach 12 volts, they‘re no use for them. I recommend replacing them. As far as which batteries to use, I suggest deep cycle batteries, not car batteries. They can be flooded…but for mobility scooters its best to use sealed batteries like AGM or Gel.

      Reply  •  June 26, 2012 at 10:55 am
  • Steve Tannenbaum
    I have a question about battery charging from a solar panel. The solar charge controller uses a mosfet to act as a switch. If the voltage on the battery increases to a certain level, then the mosfet opens and disconnects the solar panel. What happens if my solar panel puts out 24 volts instead of 15-16 volts? Will the higher voltage but lower current of the panel cause any charging problems?

    Reply  •  June 22, 2012 at 4:18 pm
    • BatteryStuff Tech
      12 volt solar panels can reach as high as 21-24 volts if the sunlight is direct. The controller should have specs regarding the maximum voltage input it can handle. Even though the controller is, like you said, a switch, it also lowers the charge voltage, too. Most of our controllers lower the voltage to a safe 14.4-14.8 volts. Therefore, 24 volts incoming from the panel is no problem for the battery.

      Reply  •  June 25, 2012 at 8:39 am
  • Josh
    in a 24 volt system, batteries connected in series, if one battery happens to fail, should both batteries be changed regardless of whether or not the 2nd battery tests out fine? also, in the same system, if one would be required to boost the 24volt system from a another source being a 12 volt source… does one connect battery positive from boosting source to battery positive of battery require boosting, negative to negative of only one battery?
    This seems like it could cause a problem as battery 1 is connected to battery 2 in series which means, battery + of one is connected to battery – of the second, wouldn‘t boosting cause problems?? how does one go about doing this safely to himself and the machine being boosted.

    Reply  •  Rated article 5  •  June 15, 2012 at 10:36 am
    • BatteryStuff Tech
      If one battery fails, it‘s recommended to replace both because battery banks composed of batteries of different ages will charge and discharge unevenly. With the 12 volt boost, it looks like one battery is being discharged more than another. This is a problem. The second battery, even though connected in series with the first, is untouched by the boost because the connections are only attached to the first battery. But having a 24 volt system, both batteries act as one single unit. Uneven charge levels will cause early battery failure and poor performance. I would use the boost option as sparingly as possible.

      Reply  •  June 15, 2012 at 2:57 pm
  • Graham Bennett
    Dear Sir,What is the best/correct proceedure when charging a 12v battery,used for a golf trolley.When fully charged,is best to keep it on charge,or remove it from the power supply?. Thanks.

    Reply  •  Rated article 4  •  June 14, 2012 at 1:28 am
    • BatteryStuff Tech
      The best thing you can do for batteries is keep them in a fully charged state whenever possible. If your charging system will not overcharge, but will adjust and trickle down to a float charge, then it‘s safe to leave on indefinitely. If not, please remove after it‘s done charging.

      Reply  •  June 14, 2012 at 8:54 am
  • Graham Bennett
    My question is,do you keep a 12volt battery(used for a golf trolley)constantly on charge,or remove from charge when fully charged?.thanks.

    Reply  •  June 12, 2012 at 3:14 am
    • BatteryStuff Tech
      It really depends on the charger you use. If it is a manual constant current charger, then I would remove the batteries after they‘re fully charged. If the unit is a smart charger, like the 3-stage microprocessor controlled chargers we sell, then it‘s safe to leave on the battery forever. Keeping the battery in the “float mode” will ensure full charge at all times, which is the healthiest thing you can do for a battery.

      Reply  •  June 12, 2012 at 1:31 pm
  • Tim
    I live in a 3rd world country. Distilled water is not available here. Can I safely use the water out of my Katydyn Filter to add back water to my starter battery? The water going in is either rain water or river water; it is not treated chemically. If it is not acceptable for the battery, what are my options for adding water to the battery? Thanks in advance!

    Reply  •  June 10, 2012 at 1:06 pm
    • Sam
      Distilled water is just captured steam. If you boil water and capture/cool the stream back into water, that‘s distilled water. You can pretty easily make your own with household supplies or even camping supplies. There are several methods out there. Google “How to distill water.”

      Reply  •  July 11, 2012 at 5:14 pm
      • BatteryStuff Tech
        That‘s a very good idea. Thank you for sharing.

        Reply  •  July 12, 2012 at 8:47 am
    • BatteryStuff Tech
      Distilled water is best because there are no impurities. Using other water will technically work, but the battery will not perform or last we long as it would otherwise. Having foreign contaminants and minerals will throw off the delicate chemistry of the electrolyte, and throw of the pH levels, too. Filtered water will work better than rain water. But anything more than pure H20 will negatively affect the battery.

      Reply  •  June 12, 2012 at 12:18 pm
  • Fred Harris
    Great article, Learned much, but, and there is always a but, started looking at batteries and found the amp hour rating listed in different ways – examples:
    20 amp hour rate:55
    35 Amp Hour
    32 Min @ 10 Amp
    So I am again confused about the true meaning of the amp hour.
    I think this is what I need to look for as I am looking for batteries for a trolling motor.

    Reply  •  June 9, 2012 at 7:13 am
    • BatteryStuff Tech
      Amp ratings are tricky. They really depend on two things: Draw amount, (Amps) and time. The first rating, 55 AH at 20 hours means that during a 20 hour load time, it takes 55 amps to discharge the battery completely. I do not know what time frame the second rating is for, possible taken at 10 hours?. The third rating tells you if you draw a steady amount of 10 amps, the battery should last you 32 minutes. The first rating, 55 AH, is equivalent of 2.75 amps an hour. But if you bump it up to a rate of 10 amps per hour, your duration is drastically cut to 32 minutes.

      Check out our battery load run time calculator to figure out what length of time a battery would give you under a load of your choice. Plus, there‘s also an article about Pukert‘s Law, which explains all about Battery Capacity. You should find that very informational.

      Reply  •  June 12, 2012 at 12:10 pm
  • Art
    I have two deep cycle dp24 12 volt batteries. One is rated 685 CA 32degrees and the other is 505 ca 32 degrees, the first is rated at 140 minutes and the other is 120 minutes. Can these be connected in parallel without problems? Can they also be charged in parallel using one charger?

    Reply  •  June 5, 2012 at 5:08 am
    • BatteryStuff Tech
      Yes, they can be paralleled together, but it‘s not advised. It will technically work. But charging and discharging will be un-even. There‘s no way around that. If you desperately need it, I say go ahead. But in the long term there may be some issues and maybe shortened battery life as a result.

      Reply  •  June 5, 2012 at 11:32 am
      • Jim
        Sounds like a similar problem we have had with one of our vehicles. It is an F350 Truck with a box that has a communications package. The truck has two batteries under the hood with green eyes. There is a third and much larger battery in the box that powers the inverters for the comms. Twice over the past 3.5 years the charging system has overheated the large battery until it failed. Last time the battery boiled over and we had a mess to clean up. The charging system is powered by a shore line that plugs into 125v wall receptacle. There has been some modifications to the systems and there is not sufficient info with the vehicle from the manufacturer that explains the 12 vots systems, but from what I understand the shore power charges all three batteries. I assume I need to check if all three are charged by the same charger. What happens to MFLA batteries if they are mixed like this?

        Reply  •  Rated article 5  •  March 27, 2013 at 4:32 am
  • Gary Mack
    I have recently purchased four new US Battery 12V Deep Cycle golf cart batteries for my 2006 Club Car, which has a 48V motor. I don‘t drive the cart more than 1-2 miles on a given day but always recharge the batteries every day of use. The Club Car charger is left plugged into the cart at all times the cart is not in use. I am getting an awful smell after the meter on the charger drops to about 4 amps…on its way to zero on the charging cycle. I can hear the electrolyte bubbling inside the batteries and they do not get hot whatsoever. Once the meter reads zero amps and the charging cycle has ended, the smell stops. Is this normal? Factory personnel tell me they will always smell when recharging…..but I have never experienced this with former Trojan (Club Car) batteries. The local dealer says the smell should stop shortly…otherwise there may be a problem with one of the new batteries. My voltmeter shows 12.7v in each of the four batteries after charging.

    Reply  •  June 3, 2012 at 9:14 pm
    • BatteryStuff Tech
      Some bubbling and smell of sulfur is normal for large flooded batteries. 12.7 volts is good voltage. As long as you monitor the water levels, it sounds like everything else is fine. If the electrolyte boils over, or completely evaporates, that‘s a problem.

      Reply  •  June 5, 2012 at 11:30 am
  • Carlos
    I have four 110AH leisure batteries for my small hybrid solar system. The batteries are all 2yrs old and are not holding their charge like they once did. I read somewhere that I could empty and wash them out then replace with a mixture of sulphuric acid(96%) with distilled water to the correct gravity, put them on a trickle charge for 36hrs and then they will be better than new… Is this true? And if so, how can I be sure my mixture is correct? I do have a basic hydrometer. Many thanks!

    Reply  •  Rated article 5  •  May 28, 2012 at 12:16 pm
    • BatteryStuff Tech
      We strongly advise against emptying out the electrolyte. Bad batteries are not a result of the electrolyte being “bad”, but usually there is a build up of sulfation on the plates in the cells. When exposed to oxygen, the sulfation will rapidly increase. Putting new acid sounds nice, but here‘s the problem. Sulfation is like trying to wash your hands while wearing gloves. You still won‘t see a full charge. On top of that, if you remove the sulfation from the plates using a pulse charger/unit, then it will become electrolyte and throw off your pH levels again when mixed with the new stuff.

      It‘s safer to simply use a de-sulfation unit like Battery MINDer or Pulse Tech for an extended period of time. That‘s what we do.

      Reply  •  May 29, 2012 at 8:56 am
  • Timothy Lee
    I have a 12V marine deep cycle battery which is marked 875 marine cranking amps, 675 cold cranking amps, and 125 amp hours. I have been using the battery on my boat for about two years since I purchased it. It was charged every couple of months by either running the engine (a 9.9 HP outboard with an alternator which puts out less than 10 amps at full throttle) or by using a regular car battery charger with a pulsating charge of 10 amps(duty cycle= 10 sec. on, 140 sec. off). It only serves the bilge pump when the boat is not in use, and the pump only runs a few times a day for a few seconds. After not checking it for about two months, I found that my battery was not working (boat bilge was flooded) so I brought the battery out of the boat to my house. Prior to charging, it read about 6 volts on the meter, and it was low on water. Each cell had about 1/4 in. of the cell showing, and I added about 4 oz. of distilled water to each cell. I charged it for about 50 hours with the 10 amp charger, and after reading your article, I changed to a 1 amp charger. I now have access to a hydrometer, and I will stop the 1 amp charge tomorrow morning, and let the battery set for a while before checking with volt meter and hydrometer. The 10 amp charger still reads about 9 amps on its meter when charging, and immediately after I disconnected it, the voltmeter showed 12.46 volts. All cells were bubbling, and the battery was warm, about 100 F. What have I done wrong so far? Could I have damaged the battery? Do you think it will recover from the deep discharge?

    Reply  •  May 26, 2012 at 7:27 am
    • BatteryStuff Tech
      12.46 volts is good progress. You probably won‘t be able to see a full charge because of sulfation build up. It‘s like trying to wash your hands while wearing gloves. I don‘t believe the battery is beyond repair, but I strongly recommend a desulfator or charger with desulfation pulse mode (not voltage pulse, like some chargers do). Try a Battery MINDer or Pulse Tech unit.

      Reply  •  May 29, 2012 at 8:18 am
  • Mat
    is it possible to charge a 12 V battery with less than 12v?

    Reply  •  May 21, 2012 at 1:00 pm
    • BatteryStuff Tech
      Yes, but not fully. Proper charging requires inputting a higher voltage in order to bring up the battery voltage. For example, if your 12 volt battery is reading less than 6 volts, you can use a 6 volt charger to bring it up to 6.6 volts. At this point you may use an 8 volt charger. But a 12 volt battery reading less than 10 volts is still EXTREMEMLY discharged, and should be brought back ASAP to avoid sulfation and decreased battery life. Please use a 12 volt charger, or make sure the charging system in your application is strong enough, usually 14.6 volts is normal.

      Reply  •  May 22, 2012 at 9:58 am
  • Vince
    I have a cpep that uses 2.2 amp I need to run it of a deep cell and a inverter for 8 hour for camping what what size inverter and deep cell battery would I need?

    Reply  •  May 21, 2012 at 11:20 am
    • BatteryStuff Tech
      Please use our online calculators to find the answer. They are located at /kb/tools/ and they are very easy to use.

      Reply  •  May 22, 2012 at 9:46 am
  • Justin
    i have a 12 volt trolling motor and i just purchased an optima bluetop battery. These batteries are marketed as being dual purpose (deep cycle and cranking). is it possible to connect two 12 volt batteries to power my trolling motor (i want to be on the water as long as possible) and if so could i than use one of those 12 volt optima blue top dual purpose batteries as my cranking battery for my engine? if any of this sounds dumb im sorry im very new to boating and im trying to figure all this out .

    Reply  •  Rated article 5  •  May 20, 2012 at 3:37 pm
    • BatteryStuff Tech
      Deep Cycle batteries have a CCA rating as well. If you have a starting battery and a deep cycle battery of the same physical size, the starting battery will have far more CCA. It has to do the the thickness and number of the plates per cell. But if you have a large marine battery, there‘s a good chance there will be enough CCA to turn over your engine. It‘s not unheard of. There‘s no harm in trying it out. It will either work or it won‘t.

      Reply  •  May 22, 2012 at 10:27 am
  • Bob
    The best ever. Your tutorials were written for dummies like myself.

    Reply  •  Rated article 5  •  May 17, 2012 at 6:46 pm
    • BatteryStuff Tech
      Thank you for the feedback. :)

      Reply  •  May 18, 2012 at 9:22 am
  • Kamran Jabbar
    When we use two batteries 12V each in a 24V system connected in parallel. There will be a possibility of unbalancing if both the batteries have different manufacturing date or batch. The charger only knows to charge 24V even if one battery is at 14 and other one is at 10. So it is thumb rule always connect same batch batteries in series and never replace one battery in a series. Replace the whole bank to avoid unbalancing. Unbalancing can damage one battery earlier than expected life.

    Reply  •  May 16, 2012 at 4:23 am
    • BatteryStuff Tech
      Well said. Thank you for contributing.

      Reply  •  May 16, 2012 at 2:44 pm
  • Yloon
    I have been charging my dead battery for 4 months using pulsetech smart charger. This dead battery has been leaving there for 1 year.
    I got back my voltage of 13.7v and the smart charger is pulsing without mass charging for 1 week.
    However the battery still unable to start my car. The battery can supply headlight, horn and etc.

    Should i give up this battery or any other way to try it out?

    I notice 1 of the electrolyte‘s in a cell is not drying up even after a long charge. the other cells always keep drying up and require to top up with battery water. Is the cell dead and cannot be revive anymore?


    Reply  •  May 14, 2012 at 10:35 pm
    • BatteryStuff Tech
      Please refer to our article about Battery Troubleshooting. As far as battery water goes, as long as it‘s distilled water, that‘s fine.

      Reply  •  May 16, 2012 at 10:53 am
  • S.
    My husband just added acid instead of distilled water to my motorcycle battery after it had been sitting all winter. Is it ruined?

    Reply  •  Rated article 5  •  May 9, 2012 at 4:09 pm
    • BatteryStuff Tech
      Possibly. The sulfuric acid never leaves the battery, it‘s only the water that evaporates and needs replenishment. If more acid was put in, the pH levels are probably out of balance. The battery may still work, you should test it before going on the road with it.

      Reply  •  May 9, 2012 at 4:17 pm
  • Jim
    Off the beaten track but several years ago my Dad bought me a 16V Craftsman drill. I used it a couple times and put it in the garage. Recently I was cleaning up and found that drill but the battery was dead and refused to take a charge no matter what. A new battery (when they can be found) is $55 plus. Do you know of any way to get this battery working again? Thanks.

    Reply  •  Rated article 5  •  May 8, 2012 at 11:48 am
    • BatteryStuff Tech
      We sell a variety of power tool replacement batteries. You can view our selection at /batteries/power-tool-batteries/

      Rebuilding a power tool battery pack will run around $30-35 and up. We will be offering battery rebuilding in the near future.

      Reply  •  May 8, 2012 at 12:02 pm
  • Jack Gilbert
    Great info, my battery died today, so, the AAA guy said that my old battery was below 12.5 volts and that it wouldn‘t have or hold the amps?? what does this mean

    Reply  •  Rated article 5  •  May 5, 2012 at 8:09 pm
    • BatteryStuff Tech
      12.5 volts is partially discharged, 70% capacity remaining. When a battery is put under a load and there are no “amps” going through, it‘s usually a result of an open cell. The intense heat of a load can cause a separation in a cell connector, and this will cause current to decline or cease entirely. But when the load if taken off, the metal cools enough to touch and give a false voltage reading. It‘s very misleading and a result of poor construction at the factory level.

      Reply  •  May 7, 2012 at 12:36 pm
  • Trev
    i might have missed this in the article but, why is it not recommended to mix battery sizes, and not to mix battery types?

    Reply  •  Rated article 5  •  April 23, 2012 at 9:51 pm
    • BatteryStuff Tech
      Batteries of different types and sizes will charge and discharge unevenly. When batteries are configured in parallel or series (or both) they behave as a single unit. If there is an imbalance it could mean a shortening of overall battery life, as well as potential harm in recharging.

      Reply  •  April 24, 2012 at 11:49 am
  • Dave
    I have a question. I purchased a Minn Kota Endura 50 trolling motor 2nd hand. It‘s for an aluminum fishing boat I have access to once a year for a week. I‘m a casual fisherman who takes the boat out maybe for an hour a day. I bought a deep cycle AGM 12 Volt 12 amp hour with a charger for agm and gel batteries. I had trouble finding what kind of draw the trolling motor places on the battery at the Minn Kota site. Did I buy an undersized battery for my causal usage?

    Reply  •  April 20, 2012 at 3:29 pm
    • BatteryStuff Tech
      Speaking from experience with other customers with trolling motors, I can‘t imagine the motor pulling anything less than 15 amps/hour from the battery. A 12 AH battery would not be able to supply more than 1/2 hour of power to the motor, if even that much. A larger capacity deep cycle battery would be highly recommened.

      Reply  •  April 20, 2012 at 4:10 pm
      • Dave
        I was afraid of that. Any suggestions as to what would fill my needs but would not be overbuying for what I do? I see some of the deep cycles run $400 or more. I don‘t think I need that much power. Thanks for your reply. Obviously I‘m new to making these calculations and a little leery of just walking into a store and having them sell me something.

        Reply  •  April 21, 2012 at 4:42 am
        • BatteryStuff Tech
          If the motor drew at a rate of 15 amps an hour, I recommend using a group size 24 marine battery. This 12 volt, ~75 Amp Hour battery should give you 2 hours of uninterrupted runtime, and only discharge the battery to the safe 50% capacity remaining. We sell these batteries for $200-250.

          Reply  •  April 23, 2012 at 8:46 am
  • Bill
    I asked a question a few weeks ago and have been looking for a reply. My question is about running LED lights on a 12v vs a 24 volt system. I have 17 lights that are 27 watts each and want to get the maximum runtime. I have seen your calculators but do not have all the imput parameters. The batteries I am thinking about are deep cycle with 210 reserve capacity. Thanks.

    Reply  •  Rated article 5  •  April 16, 2012 at 1:15 pm
    • BatteryStuff Tech
      My question is this: what voltage are those lights rated for? If it doesn‘t say on the lights, you should find out by calling the maker. It‘s important to keep the voltage the same. Running a 12 volt rated LED light bulb will blow up if you use 24 volts (2 batteries in series). Maximum runtime is ensured not my increasing the volatge amount, but the capacity (Amp Hours).

      Reply  •  April 16, 2012 at 2:34 pm
  • Frank
    Virgin lead vs. recycled lead?

    Is there a life span difference between batteries constructed with virgin lead compared to one made with recycled batteries, assuming that all other conditions are equal? If there is a difference, is it a noticeable one?

    Reply  •  Rated article 4  •  April 16, 2012 at 9:30 am
    • BatteryStuff Tech
      Yes. Batteries made from virgin-lead perform better and will last longer. High performance batteries, such as Odyssey, also have 2 year warranties.

      Reply  •  April 16, 2012 at 11:19 am
  • Budge
    I have a 12 volt portable battery (Sears Diehard Portable Power 1150) that I use for car camping trips and the occasional jumpstart. I wasn‘t keeping it charged all the time and the battery finally wouldn‘t take a charge anymore. So I was convinced to replaced it with a deep cycle agm battery. After reading your article, it seems apparent that I should not have used a deep cycle because it‘s not appropriate for jumpstarts. However, I have also found that after the first time I used the battery for a weekend of camping, I had drained it down to 10% and now it will not charge. Is it possible that the unit is not compatible with deep cycle batteries, or is it more likely that I overdrained it and the unit isn‘t registering a battery to charge? I was told that I can connect this unit to my car battery (or any other charged 12 volt battery) and that should trick the unit into charging the battery. What do you think?

    Reply  •  Rated article 5  •  April 10, 2012 at 12:27 pm
    • BatteryStuff Tech
      Deep Cycle batteries have CCA ratings as well. However, for the same physical size battery, if you compare it to a starting battery, the CCA will be much less. But a deep cycle battery is fairly common in jumpstarts because they are also used as 12 volt power sources and some even have built in inverters for AC power. The batteries in the units are large enough where the CCA can jump start a car. In doing so, 25% of the battery‘s capacity can be drained just like that. If batteries read severely low voltage, most automatic chargers have trouble charging. Connecting another battery in parallel with the drained battery is a good method of bypassing the “low voltage disconnect” filter of the charger.

      Reply  •  April 10, 2012 at 2:06 pm
  • Tom
    Lots of good stuff here—-and well written so that weekend mechanics like me can understand it. I have a 36v Western Golf Car with 2 year old batteries. The charger came with the car and I recharge after every use. None-the-less, two cells have failed on each of two of the batteries. Your article recommended that I should not ‘mix and match’ batteries, but I would like to replace the two failing batteries with new ones to get another year or so out of the remaining 4 old batteries. They cost about $125 each so my fix would invest $250 now to stave off a $750 pay out for another year. Bottom line: If I follow your advice, I replace all batteries at the same time and chuck 4 fairly good batteries (with no resale value). Is there a middle ground—-such as using some of your products to bring the two batteries back to service??

    Reply  •  April 9, 2012 at 4:38 am
    • BatteryStuff Tech
      The choice is yours. The reason we recommend using batteries of the same age is because you will see overall better performance and lifespan of the whole bank if you do this. But if you feel it‘s not practical, you buying 2 new batteries will make your bank work and it might be just fine for you. It‘s not optimal, but it makes more sense. If your old batteries have shot cells, there is no product that can reverse that.

      Reply  •  April 9, 2012 at 9:35 am
  • Chad
    Excellent information. Thanks.

    Just bought a DieHard Platinum Marine Group 31 for my boat. The reviews on this battery are excellent and I plan to use it for both starting the boat and running the trolling motor. You mentioned needing a special charger for AGM batteries. I have a Stanley BC4009 40 amp 3 stage charger. Is this charger OK to use with the AGM battery? Do I have to disconnect the battery from the power cables to charge it? Thanks for your help!

    Reply  •  April 7, 2012 at 1:16 pm
    • BatteryStuff Tech
      AGM Batteries can be charged with most standard chargers. It‘s the Gel batteries that require a special charge profile. If you charge your battery, you don‘t have to disconnect the power cables as long as the battery isn‘t being used while you charge it, unless your charger is also a power supply. If you draw on the battery while the charger is turned on, the charger will attempt to supply the demand.

      Reply  •  April 9, 2012 at 9:23 am
      • John
        Well then, if a modern automobile with all it‘s current drawing electronics is to be charged using a smart charger, are you suggesting that the cables be disconnected while charging the battery? What difference would it make if cables were left on during the charging process? Thanx

        Reply  •  August 17, 2012 at 2:03 pm
        • BatteryStuff Tech
          Having the battery connected to the vehicle will cause a slight discharge as a result of the electronics. But normally it‘s not much. A charger will stil charge just fine but if the draw amount of the car is excessive, it can cause the charger to become less efficient.

          Reply  •  August 17, 2012 at 2:20 pm
  • Bobby
    A very useful site, and highly informative – well done!

    I have two flooded lead acid for my domestic bank, and have added a small AGM for the engine start. The mains charger can be configured for one type or the other – in my situation would it be better to set the charger to AGM type?


    Reply  •  March 31, 2012 at 6:46 am
    • BatteryStuff Tech
      From our experience, Flooded and AGM batteries can be charged at the same charge voltages. It should be safe either way.

      Reply  •  April 2, 2012 at 8:16 am
  • Rich

    I have a boat with 2 cyl diesel engine and currently 2 series 27 wet batteries set as two banks. I would like to add another 2 batteries because the engine does not start easily when cold. The question is whether it is advisable to mix AGM‘s as one bank with wet cells as the other. I would like to change to AGM‘s, but hate to lose the investment already made in the two wet batteries. For starting, I do have a standard A/B or BOTH as a switching option for the banks.

    Reply  •  March 28, 2012 at 7:23 am
    • James Ville
      When constructing battery banks, it‘s highly recommened to use batteries of the same type (Flooded, AGM, Gel), voltage, AH rating, and even age. Although you can technically build your banks by adding AGM batteries, having these differences will cause an inbalance of discharge and recharging.

      Reply  •  March 28, 2012 at 8:01 am
  • Bill Smith
    Thank you for that info. Well meaning folks online were driving me nuts telling me that a deep cycle battery that is often discharged to 50 percent will greatly shorten the life of a small alternator. But I couldn‘t find any info like that at a reputable web site and I‘m glad to hear it isn‘t really true. I had been looking at a VSR (voltage sensitive relay) for the part of the wiring you mentioned. These (I guess they are all the same) charge the starting battery first and then switch the charging current to the auxiliary battery. Does the isolator you mentioned work that way? If not, which method do you think is best. I know the companies that make the VSR devices are always touting the fact that there is no voltage drop with their devices which I gather there is with a device that uses a solenoid.

    Reply  •  Rated article 5  •  March 23, 2012 at 11:27 am
  • Andrew D-H
    Awesome article – thanks. I have a question.
    I have a YP17-12 (12V17AH) Maintenance Free Lead Acid battery in my Bushranger Power Tank (for jump starting). It‘s was showing over 12 volts after about 10 hours at 1 amp. I tried to load test (it failed) and it‘s now just under 12 volts. It has a plastic strip which when I popped it off with a screwdriver there were little caps on each filling hole. Can I add distilled water to it even if it had gel. I up-ended it with caps off over a container and not a single drop of liquid came out making me think it is not a wet acid type. Your thoughts would be greatly appreciated.

    Reply  •  Rated article 5  •  March 20, 2012 at 5:22 am
    • James Ville
      If the battery is indeed maintenance free, it is not designed to be opened and water added. Low voltage is not a result of low fluid levels, in this case. A fully charged battery should read 13.2-12.8 volts. If you read 12.0 or 12.2 volts, that‘s severely discharged. If you load test at this poin, you‘ll only further discharge the battery. I recommend putting the battery on a charger immediately and load testing once it‘s fully charged.

      If the battery is draining rapidly in 10 hours at 1 amp, I recommend you use our online tools to calculate if that‘s a good size battery for that amount of draw, or if the draw time should be shortened for the sake of the battery.


      Reply  •  March 20, 2012 at 10:54 am
  • Shawn
    The article above suggests you know what you‘re talking about. I don‘t know jack, but have read a little online and am trying to use a deep-cycle battery to power a projector for a public art project. Any chance you‘re available to help me trouble-shoot? I borrowed a neighbor‘s charger and charged a brand new battery up for about 15 hours. I then hooked up a 1000watt inverter and plugged the projector in. It worked great, for about 25 minutes, but then just died with a Low Voltage error message. Does this mean the battery wasn‘t charged all the way or am I doing something else wrong? According to the projector specs, the max wattage it uses is 288. Would really appreciate any input you‘ve got. I‘m out of my league here.

    Reply  •  March 19, 2012 at 12:04 pm
    • James Ville
      Based on the information you provided, you‘re drawing around 23 amps from a 12 volt battery. That‘s a lot of juice since it‘s a constant draw, not a quick burst. Without any information about the battey itself, or the charger, I cannot determine what the problem was.

      If the battery did not have the capacity to handle the load, you may need something with more AH (Amp Hours). It might be helpful if you run your numbers through our calculators.


      Or give our tech guys a call at 541-474-4421

      Reply  •  March 19, 2012 at 12:58 pm
  • Cain
    I only use my car on weekends. My question is: Can I use a Smart Charger whenever the car is stopped? This will not overcharge the battery?
    My car has an AGM battery.
    Thanks in advance for your help.

    Reply  •  March 18, 2012 at 11:55 am
    • James Ville
      If you use an AC charger, parking the car and turning off the engine is fine. If you are refereing to a solar charger, it‘s also designed to charge the battery, not only when the car is stopped, but the engine is off as well. Plugging a smart charger on the car during the weekdays is very healthy for the battery. No overcharging if you make sure the charger is fully automatic. Our chargers are. :)

      Reply  •  March 19, 2012 at 11:30 am
  • Bill Smith
    Thank you for the excellent article and taking the time to answer everyone‘s questions. I want to install a dual battery system in a small car that has an 80 amp alternator. The 2nd battery will be dedicated to one appliance that has a low current draw. A small deep cycle AGM like those used in mobility scooters will do the trick (about 35 Ah). I don‘t want to upgrade the alternator but I also don‘t want to overly stress the one I‘ve got by having it regularly recharge a battery that is often going to be drained close to max (50 percent). Is there a way that I can limit the current to the second battery so that it charges at 10 to 15 amps? That would be equivalent to driving with lights on and so I know it would not have a big negative effect on the alternator as long as I am not using the lights.

    Reply  •  March 18, 2012 at 12:40 am
    • James Ville
      If you want to charge your vehicle‘s starting battery as well as a separate auxiliary battery, I recommend using the Battery Isolator Switch (Bi303303). Having a 35 AH spare battery should not be too much for your 80 amp alternator. It‘s an automatic device, there is no “preset” amperage setting. The charge allocated to the batteries really depends on the status of each one. With the rise in resistance in one battery, charge will be directed to the other until they are both stable and full.

      Reply  •  March 20, 2012 at 11:46 am
  • Gary
    have a 6 volt dry cell batt. in a old bike. is there a way of protecting the batt. from being over charged? thank you for your time..

    Reply  •  Rated article 4  •  March 17, 2012 at 6:33 am
    • James Ville
      The best method to preventing battery from being overcharged is to use a micro-proccessor controlled “smart” automatic battery charger. If the bike itself is over-charging, then there is a problem with the bike‘s charging system, the stator.

      Reply  •  March 19, 2012 at 11:06 am
  • Toni Roddey
    Fantastic information. Thanks so much for your service to those of us struggling to understand through all the hype. My question is for a marine application. I have a bank of 4 Trojan lead acid batteries for my house bank and another lead acid starter battery. My starter battery died and I‘d like to replace it with a maintanence-free option but have heard not to mix battery types. I‘m not ready to replace the Trojans, so should I just buy another lead-acid starter to tide me over until my Trojans die? Thanks for any suggestions you can give.

    Reply  •  Rated article 5  •  March 13, 2012 at 2:19 pm
    • James Ville
      If your starter battery is not connected to the house bank, then it‘s fine to upgrade it to a sealed type. You can even use the same charger if you go with an AGM. Within a battery bank it‘s recommended to use the same battery type. Because your boat draws from the house bank and the starting batteries separately, then you‘re okay.

      Reply  •  March 13, 2012 at 3:28 pm
  • Jummy
    hello Jamie, I am currently working on a research about Solar- hybrid off-grid instalations,
    I have my battery amp hour for 20hrs discharge but i need the battery to store enuf cahrge for 3 days, so ut is trippled, do i still use the C20 rating or do i use the C72hrs rating for it? i am confused. and the needed Current is about 6000Amp-hour

    Reply  •  Rated article 5  •  March 13, 2012 at 2:49 am
    • James Ville
      If you parallel your batteries, the capacity (AH) will increase. The rating will still be at 20 hrs, but the number will triple.

      If you have your batteries and draw amount, please use our battery calculators to help you figure out how long they will last, or if you need another battery based on your load.


      Reply  •  March 13, 2012 at 9:14 am
  • Mel Schallot
    Very good overview of lead-acid batteries. How do I submit a question? What type of sealed lead-acid battery would a handicap scooter likely have: AGM or Gel? I need to know in order to select the right charging mode for a Schauer automatic charger.

    Reply  •  March 12, 2012 at 10:46 am
    • James Ville
      Mobility Scooters use both AGM and Gel batteries. I cannot verify what you have. However, if you‘re unsure, I recommend using the Gel setting. This is a lower voltage that is safe for gel, but the AGM will accept it also. It‘s the other way around that is not recommended.

      Reply  •  March 13, 2012 at 11:56 am
  • Deron
    Next time simple is enough…..

    Reply  •  Rated article 3  •  March 12, 2012 at 10:16 am
  • Phyleus
    Wonderful article. Just had a question though.
    How does one test SMF batteries on-site for e.g. Server UPS batteries. ? The test-gig should be portable though.

    Reply  •  Rated article 5  •  March 12, 2012 at 3:30 am
    • James Ville
      What do you need to test for? Voltage readings with a volt meter is always helpful. This gives you a good idea of the state of charge of the batteries. A Load tester is good for measuring CCA and durability under a load. Even our comprehensive digital battery conductance analyzer is portable. All of our testing units are located in the Battery Accessories category on our website. See for yourself. :)

      Reply  •  March 12, 2012 at 11:58 am
  • Greg White
    James, this is a great site! Maybe you can help me: I have 3 8D AGM marine batteries on my boat with a xantrex charging system. The boatyard said they would plug the boat in over the winter in the warehouse but did not. Nor did they shut the breakers off. So, the batteries were depleted to zero over the last 5 months. How can I tell what damage was done? How can I calculate the liability the boatyard has?

    Reply  •  Rated article 5  •  March 8, 2012 at 4:21 pm
    • Knobby Ions
      hi all i bought a AGM battery for my kawasaki vn 1500, great more ca,s no probs with it until i went overseas to work and made the mistake of leaving the ignition switch turned to park!, THIS in turn left the rear lamp illuminated, returned back home 6 weeks later ZILCH,visited my local bike guru in redcar he put slow charges, then fast charges into it over a period of two days, its gone from an initial reading of 0.3 v to a steady 12.9, hope this helps the guy with the boat.

      Reply  •  May 8, 2012 at 8:53 am
      • BatteryStuff Tech
        Hey, that‘s great that your batteries came back! 12.9 is very good voltage. Thanks for sharing!

        Reply  •  May 8, 2012 at 9:59 am
    • James Ville
      While it‘s difficult to quantify the damage, I have some recommendations.

      First, you should take a voltage reading from the batteries. If indeed you‘re reading 0 volts (which is unlikely) then I would try to charge them with a low voltage start charger ASAP. Most automatic chargers have a cut-off voltage of 6.5 volts before they will start. This prevents you from bringing back severely discharged batteries. Interacter makes a charger that starts charging with a reading as low a 1-2 volts.

      Second, sulfation has most definitely occurred, so I would also advise putting a de-sulfator unit on the batteries as well, such as the OBD12V. If these do not bring the battery back to working condition, then I would suggest the batteries have passed the point of no return.

      Reply  •  March 9, 2012 at 9:30 am
  • Eagleye
    Thank you James, for all the great information!

    Ive got an electric scooter (xtreme xb-600) and need to replace the 12v22ah SLA. Ive looked around and was told that the EVX12200 or EVH12240 Deep Cycle Battery would be the way to go.

    Your opinion would be muched valued and appreciated!

    Reply  •  March 5, 2012 at 5:33 pm
    • James Ville
      Yes, those batteries will work as they are the same dimensions as any 12 volt 22 AH SLA Battery. The difference between the EVX12200 and the EVH12240 is AH rating. The higher the AH, the more runtime you‘ll have.

      Reply  •  March 6, 2012 at 8:46 am
  • Rick Echols
    Hi, I have four 6 volt house batteries for my RV. We do some warm weather dry camping. How low should I let the voltage drop before recharging with the generator? Thanks, Rick

    Reply  •  March 2, 2012 at 9:06 am
    • James Ville
      Lead Acid Batteries, doesn‘t matter the voltage, should never be left to drop in voltage. That is only common practice with NiCD batteries. Discharging your batteries severely before recharging them will cause sulfation and early battery failure. The healthiest thing to do is keep them fully charged as often as possible.

      Reply  •  March 2, 2012 at 9:11 am
      • Rick Echols
        So how can I expect to be able to use my house batteries for dry camping without losing any voltage? I would think that I should be able to use my lights inside and radio without runnung my generator. I don‘t want to have to run my generator all the time.

        Reply  •  March 2, 2012 at 9:25 am
        • James Ville
          Losing voltage is normal. Good battery maintenance is as follows: Re-charge battery at the soonest possible after using the battery. When drawing from the battery, avoid discharging below 50% capacity. This is the danger of having a battery sit in storage for months at a time. You will see early battery failure. Charging regularly or keeping a trickle charger is the best solution.

          Surely batteries are meant to be used. But the myth of “battery memory” does not apply to lead acid batteries. It is not healthy, and unnecessary, to discharge all the way and recharge again.

          Reply  •  March 2, 2012 at 9:35 am
  • John Paciorek
    I have a Sportster scooter which is seven years old and has two 12V deep cell GEL type batteries. It has been used very little. These batteries won‘t take a charge. When I disconnect them to read the voltage I get 11 volts on one and 13 volts on the other. Gel types (80AH) for this unit are super expensive.
    (1)Could I try to replace the 11 volt battery only, presuming its a dead cell?
    (2)Would you recommend that I replace these batteries with two AGM batteries with a comparable AH rating? Can I use the same charger on these batteries?
    (3) Any other way out of this dilemma, such as using a maintenance-free lead acid battery with a comparable AH?

    Thanks very much, John
    Thanks very much

    Reply  •  March 2, 2012 at 6:07 am
    • Ranger
      How is that one would determine that an 11 volt reading is not associated with a shorted cell?

      Reply  •  Rated article 4  •  June 19, 2012 at 11:20 am
      • BatteryStuff Tech
        11 volts cannot be a short cell, as each cell can read 2 volts or more. Therefore, a battery with a short cell typically reads 10.5 volts or less. But an open cell is different. This has to do with a weld piece disconnecting under the load, and voltage usually drops significantly or sometimes flatlines when this happens.

        Reply  •  June 20, 2012 at 12:41 pm
    • James Ville
      1) If you‘re reading 11 volts, there is no short or dead cell. It‘s much less expensive purchasing a de-sulfator unit to restore the battery than to buy a new one. If the batteries are still holding a charge, they can be restored.
      2) If you do decide to upgrade to AGM, your Gel charger will work. Commonly, AGM batteries charge best at a higher voltage, but those chargers would damage the Gel.
      3) When creating a battery bank, it‘s recommended to use batteries of the same voltage, AH rating, and type. 80AH AGM batteries will work for your system just fine, but good battery maintenance is still recommended, regardless of the battery chemistry type.

      Reply  •  March 2, 2012 at 9:29 am
  • Tom Z
    I have an interesting battery question for AGM battery charging. I recently purchased a 12 volt 7 amp battery for my roboduck, I used my older 1/2 amp charger adn about two hours later, I noticed the battery had a puddle of clear water around it‘s base. It was acid! How on earth could a glass matt battery generate that much fluid (about 1/4 cup). I did nto even think there was that much fluid in the battery! What is going on?

    Reply  •  February 29, 2012 at 9:55 am
    • James Ville
      span class="caps">AGM batteries are sealed. If there is a large pool of electrolyte, there must be an opening in the case. If the liquid is not coming from the ventilation holes on the top, there must be physical damage elsewhere, possible near the base.

      The electrolyte in the battery is absorbed, but it can be forced out if there is enough pressure in the case or if it hasn‘t had time to fully absorb (for instance, it if was a freshly activated battery).

      Reply  •  February 29, 2012 at 10:04 am
  • Yancy
    I‘m shopping for a couple of off-grid batteries , I‘m curious when purchasing a new battery, what is the typical warranty length, in case you bought a dud that was sitting in the heat in storage for 12 months. Thanks, great info BTW

    Reply  •  Rated article 5  •  February 24, 2012 at 11:33 am
    • James Ville
      All of our batteries have their warranties listed on the product pages. Typical warranties start at 1 year for most of our powersports batteries. Shorai and Odyssey high performance batteries have 2 year warranties.

      Reply  •  February 24, 2012 at 11:56 am
  • John C
    Great informative article. Just wondered if you or any of your readers have experienced or heard of problems with BMW automobile batteries? This is a well know and documented issue by many BMW owners and dealers? Due to the inordinate number of battery life failures BMW no longer honors their new car battery warranty. By downloading historical information from the automobile‘s computer the dealer will look for any excuse for blaming the problem on the car owner, e.g., leaving the door open, leaving the key in the car, or not driving the car for several weeks. It seems to me that BMW has a problem with parasitic drain on their cars from about the time that the 2008 models came out. The car computer remains active when the engine is off, still controlling functions that I cannot explain. BMW has not compensated for this parasitic drain by installing a heaver duty (more Amp Hours) battery. I can‘t believe their engineers are this ignorant. An easy saluting would be to parallel two batteries but this would increase the cost of the vehicle by several hundred dollars. That is probably why BMW has taken no action to correct the problem. It is possible that other automobile manufacturers have similar problems. My opinion is that if new batteries cannot be designed to compensate for the heavy parasitic drain then the manufactures need to install two parallel batteries or come up with procedures to connect an external battery trickle changer when the car is parked overnight.

    Reply  •  February 23, 2012 at 5:43 pm
    • Keith Vanderee
      span class="caps">BMW cars and some Mercedes Benz have had issues with on board computers,after disconnecting the engine heater wiring and computer reset the problem was solved. Disconnect the battery,disconnect the heater wiring at engine, reconnect battery, turn on ignition 20 seconds, turn off. Then start engine, if no startyou have to reconnect the wiring on some models warning fault light will stay on for some time. Our workshop solved most problems.
      Over sophisticated temp (seats, engine) and security sensors and free radical computer connections can create the power use problem. If you can find a reset button/or code it helps.

      Reply  •  June 25, 2014 at 1:29 am
      • BatteryStuff Tech
        Good advice, thanks!

        Reply  •  June 25, 2014 at 9:00 am
    • James Ville
      That‘s a good suggestion. A Trickle Charger is the best step to take in extending the life of the battery. It‘s less expensive than a new battery, that‘s for sure.

      Reply  •  February 24, 2012 at 7:49 am
  • Todd
    I am purchasing a 125 watt solar panel and want to purchase two 12 volt RV batteries.I dry camp alot and want to be able to maximize my reserve capacity using the solar charging to replenish the drain on the batteries. My question is what size battery re the 20 hr amp rating would you recommend using two twelves and AGM or Gel? I do not winter camp so majority of use is April to Oct. Apprecite your expertise.

    Thanks TP

    Reply  •  February 22, 2012 at 6:21 pm
    • James Ville
      If want to size the batteries, you will need to know your load amount. If you have this, please use our Sizing a 12 Volt Battery to a Load Calculator found here:


      If your solar controller has a gel profile, then having a gel battery is not a problem. They can deep discharge better than AGM, but are more expensive.

      Reply  •  February 23, 2012 at 12:01 pm
  • Z
    I have a few questions about sulfation removal.

    1. How can a person determine how much sulfation has occurred inside a battery?
    2. Which de-sulfation device do you most highly recommend to remove sulfation from battery plates?
    3. How much time is required to fully de-desulfate a battery? If the de-sulfation device isn‘t capable of fully de-sulfating a battery, can you let me know how much de-sulfation such a device can provide.

    Thx, Z

    Reply  •  February 17, 2012 at 4:37 am
    • James
      1)There is no exact way to determine the amount of sulfation, but a hydrometer is helpful. By telling the specific gravity, you can determine the strength of the electrolyte. Typically, the more sulfation on the plates, the weaker the strength of electrolyte. If you have sealed batteries, a hydrometer will not work.
      2)If you have a flooded battery, I recommend using Battery Equalizer in conjunction with a pulsing charging, such as Battery MINDer or PulseTech. Exact model will depend on the capacity of your battery.
      3)You’ll see the most dramatic results after about 2 weeks of continuous pulsing. The harder, crystallized sulfate which took a long time to build up may take an additional 2 months before reaching a another restore point. On average, a de-sulfated battery may be restored up to 80% of its original factory capacity.

      Reply  •  February 17, 2012 at 9:58 am
  • Kris F
    hey, i am trying to charge 2 deep cycles in parallel with a 6 amp charger (12v) is this any diffrent than charging a single?

    Reply  •  February 16, 2012 at 1:10 am
    • James
      When you charge 2 deep cycle batteries in parallel, you’ve essentially doubled your capacity. The charger will recognize your battery bank as a single battery. If your 6 amp charger took 4 hours to charge one battery, it will now take 8 to charge both. The resistance has increased with the increase in capacity, so it will take longer to charge. As for the connections, you can hook your charger to the positive and negative terminal from one battery or both. For a 2 battery system, it doesn’t make a difference.

      Reply  •  Rated article 5  •  February 16, 2012 at 8:32 am
      • Paul
        “The resistance has increased with the increase in capacity,” Not so, resistances in parallel decrease. It takes longer to charge because you are charging two batteries at the same time instead of one.

        Reply  •  April 15, 2012 at 8:49 am
        • BatteryStuff Tech
          Resistance is based on the internal battery chemistry. It‘s not constant, but it relates to the strength of the charge rate versus the state of charge in the batteries. Two batteries in parallel will indeed lower the resistance. The charge time may not be quicker, but it will be more efficient.

          Reply  •  April 16, 2012 at 11:03 am
  • Denise Keilholtz
    hi I am extremely interested in the subject and would like to thank you for clearing up a few things that i had previously not known.

    Reply  •  February 14, 2012 at 4:31 pm
  • Bob G
    Two weeks ago I purchased a new car Buick Enclave that had been on the lot for an extended period of time. Everything seemed to be fine until I took a long trip (10hrs). The next morning I used the remote start to warm up the car then turned it off and continued to load the car using the remote hatch lift several times. About ten minutes later I got in the car and didn‘t have enough battery to start it. I was able to get a boost to start the engine and return home (10hrs). I took the car to the dealer the next morning to have it checked out and was told the battery was good as it checked out at 12.3 volts. Doesn‘t that show a discharged battery? Should the charging system maintain the battery at 12.6 to 12.8 volts? The next step is to have the electrical output checked. I would appreciate your input as to what I should have them check next. Thanks

    Reply  •  February 9, 2012 at 2:20 pm
    • James Ville
      Hello Bob,

      You are correct. The battery should be reading more than 12.3 volts. If the battery cannot reach over 12.6 volts, then there is likely a sulfation problem. the more sulfation on the plates, the less surface area. in turn, that results to less power and pre-mature failure.

      Reply  •  February 9, 2012 at 2:50 pm
      • Lester Cheeks
        Optimum battery voltage is 12.6 volts at 70 farenheit. Specific gravity and voltage will drop with temperature. 12.3 is a good voltage. What the battery loads down to is more important.

        Reply  •  Rated article 3  •  November 10, 2014 at 10:07 pm
  • Bert
    Hi, I have an older 4 ×4 truck with no electronics. However, I have an inverter to power (mainly laptops, gadgets), two external lights but no winch. My current alternator is rated at 75amps and my current battery at 80ams / CCA 780 / CR 120. I want to install a split batteyr system (solenoid+monitor) along with another batter (same power or slightly higher). Do I need to upgrade my alternator.. say to a 100 amps? Can a 75amp alternator comfortably charge both batteries..given than I‘m using a “smart” split battery charging system? or am I asking for trouble….ie: a dead alternator? Thanks

    Reply  •  Rated article 4  •  February 4, 2012 at 5:19 pm
    • Jeremy
      You would be best off going with the larger alternator. 75 amps may be enough, but upgrading to the 100 amp system would make sense.

      Reply  •  Rated article 5  •  February 6, 2012 at 2:40 pm
    Very important article on rechargeable batteries.

    We are planning to install Lead Gel batteries in our AS/RS equipments. Shall we go for Lead Gel or AGM type of batteries ? Why ? Give us advantages in terms of cost & safety while selecting the type of battery.
    Pls help us to decide.

    Reply  •  February 2, 2012 at 3:31 am
    • James Ville

      Gel and AGM batteries are both nice because of the maintenance free nature and sealed case. The Gels are able to deep discharge better (well, with less negative effects than the AGM). However, the Gel battery requires a compatible charger/regulator. Normal wet cels and AGM batteries effectively charge at 14.6 volts or higher. But the Gel battery should be no more than 14.2 volts. It really does make a difference. They are more fragile and can be damaged easier when charging.

      For more information, please read GEL Vs. AGM.

      Reply  •  February 2, 2012 at 8:31 am
  • John
    if i could rate your article out of ten, i would give it ten.
    very informative alas i did not solve my problem
    what is the method of getting a rechargable battery to hold charge,
    will short overcharging periods do the trick?

    Reply  •  Rated article 5  •  January 30, 2012 at 9:31 pm
    • James
      If you‘re referring to a rechargeable lead acid battery, then there could be many reasons why a battery does not “hold a charge”. There could be a parasitic drain. There could be a short or open cell. There could be an internal defect such as a weak weld. Or the battery could simply be deeply discharged, and if you‘re using a smart charger, find that the charger simply will not charge the dead battery. This is primarily due to the low voltage safety disconnect found in most microprocessor controlled chargers.

      Reply  •  January 31, 2012 at 7:44 am
  • Larry
    Is it possible to have 12 volts from a battery and low or weak cca ? Also tell me if im thinking wrong , but I have theory , that a battery is allot like your arm , you arm has the 12 volts and the muscles in your arm potentially are your amps , you can with stand holding weight for a certain amount of time until you become weak and need to relax for a few moments before you can “crank” again , would you say that would be a good example if i were to try and explain how a battery functions to people who don‘t speak english ?

    Reply  •  Rated article 5  •  January 27, 2012 at 7:15 am
    • James
      That is a good example, yes. Some arms have less muscle mass and others have more. But all the same number of muscles in the arm. 12 volt batteries all have 6 cells. Each cell is 2 volts. 2 × 6 = 12. But the cells have plates inside of them. The more plates, the more current can run through, thus more CCA. Large and small batteries all have 6 cells, but the size and number of plates can vary greatly. I hope this helps.

      Reply  •  Rated article 5  •  January 27, 2012 at 9:23 am
  • John Hackney
    Over the last 40 years I have puchased endless numbers of leisure batteries for my caravans none have ever lasted more than 12 mounths althouth I have charged them regularly.My latest one has just failed after 6 mounths and the manufacturers stamp 15 indicates January 2005 surerly this must be one of the reasons they do not last the coarse.I have found out more about batteries since reading Battery Stuff.Com although I am a retired motor engineer,Well Done.

    Reply  •  Rated article 5  •  January 26, 2012 at 11:03 am
    • Eric Roberts
      hi this is a common problem, many battery manufacturers make batteries that they claim are leisure batteries. the advice i will give is that you should buy a battery with the largest amps as possible that will fit in the space that you have, in my opinion you should buy an AGM battery as this will discharge and recover better after use, they are more expensive but should last much longer. thanks eric roberts

      Reply  •  Rated article 5  •  March 7, 2012 at 11:41 pm
      • Jamie
        span class="caps">AGM batteries do not last much longer than lead acid batteries, if they last an longer at all.

        Reply  •  June 14, 2012 at 6:01 pm
        • BatteryStuff Tech
          AGM technology is essentially the same as a lead acid battery. The only difference is the electrolyte is not free to spill, but absorbed. This eliminates the need to maintain fluid levels, thus preventing a lot of premature failure caused by reflectance. But maintenance free does not mean the freedom from having to charge regularly. All lead acid batteries self discharge, and the best way to see longest life is to keep fully charged as often as possible. Maybe you‘ve had some bad experiences with AGM batteries. That‘s unfortunate.

          Reply  •  June 15, 2012 at 8:43 am
          • Sergio
            Agreed, if properly maintained, a wet battery will last just about as long as an AGM battery. BUT, very few people actually do the proper maintenance. Because AGM batteries are valve-regulated, have a slower self-discharge rate, recharg faster, etc, etc, they are more resilient than wet batteries and therefore, in real world use DO last much longer than wet batteries.

            Reply  •  August 27, 2012 at 12:32 pm
  • Keith Clemens
    Just to let you know that your battery basics piece was well written and useful. I appreciate your hard work and your passion for your subject.

    Reply  •  Rated article 4  •  January 23, 2012 at 7:38 am
    • Wendy
      Love it!! Once I read, K.I.S.S. I knew I would understand you! Thanks!

      Reply  •  Rated article 5  •  October 27, 2013 at 10:35 am
  • Jimmy
    What is the connection to the battery tocharge a 24volt system

    Reply  •  Rated article 4  •  January 22, 2012 at 8:06 am
    • James
      If you have 2 batteries in series, the voltage increases. The most common form of 24 volt systems involves two 12 volt batteries connected together, a wire from the positive terminal of one battery to the negative on the other. For more information about constructing battery banks, read this helpful article.


      If you have a 24 volt charger, you must treat your two 12 volt batteries as if they were a single battery. The open terminals on both ends would be the required positive and negative access points.

      Reply  •  January 23, 2012 at 8:50 am
  • Desmond
    This is just what I need to give me confidence in dealing with a battery issue. Much appreciated.

    Reply  •  Rated article 5  •  January 18, 2012 at 2:04 pm