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Knowledge Base : Tutorials : Battery Articles : Battery Bank Tutorial: Joining Batteries Via Series or Parallel for Increased Power

Battery Bank Tutorial: Joining Batteries Via Series or Parallel for Increased Power

Battery Bank

What is a battery bank? No, battery banks are not some financial battery establishments. A battery bank is a result of connecting two or more batteries together for a single application. What does this accomplish? By linking batteries together, you can increase the voltage, capacity (AH / Wh), or both. When you need more power, you can construct a battery bank using widely available batteries. For instance, a deep cycle AGM or GEL cell battery in the group  24, group 27, group 31, or golf cart GC2 group size is much more affordable than purchasing a massively heavy group 4D or 8D battery for your RV, camper, trailer, or boat.

The first thing you need to know is that there are two primary ways to successfully connect two or more batteries: The first is via a series connection, and the second is called a parallel connection. Let’s start with the series method as we compare series vs. parallel.

How to wire batteries in series:

Two 6 volt batteries connected in a
series to produce 12 volts

Connecting batteries in series adds the voltage of the two batteries, but it keeps the same AH rating (also known as Amp Hours). For example, these two 6-volt batteries are wired in series now produce 12 volts, but they still have a total capacity of 10 amps.

To connect batteries in a series, use a jumper wire to connect the first battery's negative terminal to the second battery's positive terminal. This leaves you a positive terminal on the first battery and a negative one on the second battery to use for your application.

When connecting batteries: Never cross the remaining open positive and negative terminals with each other, as this will short-circuit the batteries and cause damage or injury.

Be sure the batteries you're connecting have the same voltage and capacity rating and are of the same batch. Otherwise, you may end up with charging problems and shortened battery life.

How to wire batteries in parallel:

Two 6 volt batteries hooked up in parallel that produces 6 volts but doubling the capacity. 

The other type of connection is parallel. Parallel connections will increase your capacity rating, but the voltage will stay the same. In the “Parallel” diagram, we're back to 6 volts, but the amps increase to 20 AH. It's important to note that if you plan on pulling more amperage than the system was designed for, you may need to upgrade to a heavier-duty cable to keep the wires from burning up.

To join batteries in parallel, use a jumper wire to connect positive terminals together, and another jumper wire to connect negative terminals together. This establishes negatives to negatives and positives to positives. You CAN connect your load to ONE of the batteries, which will drain both equally. However, the preferred method for keeping the batteries equalized is connecting to the positive at one end of the battery pack and the negative at the other end.

How to wire in a series-parallel configuration:

Four 6 volt batteries connected in series and parallel producing 12 volts and doubling the capacity. 

It is also possible to connect batteries in series and parallel. While this may sound confusing, it is not too hard, and we will walk you through the steps below. A series-parallel connection can increase your voltage output and the AH rating of the battery pack. To do this successfully, you need at least four batteries.

If you have two sets of batteries already connected in parallel, you can wire both sets into a series connection that will make a series-parallel battery bank. In the diagram above, we have a battery bank that produces 12 volts and has 20 amp hours.

Don't get lost now. Remember, electricity flows through a series connections like in a single battery. It can't tell the difference. Therefore, you can series two batteries that are in parallel with another set to create a series-parallel setup. For this type of setup, only one cable is needed to make the series connection which will bridge the positive terminal from one parallel bank to a negative terminal on the other.

Many customers often ask if they can put a set of batteries in series first and then parallel each set of batteries. Either way is ok, as electricity will flow through parallel or series connections the same way it would if you were only using two batteries. Many customers prefer to put their batteries in series first when using 6v batteries as it allows them to use onboard desulfators more effectively to extend battery life.

Don’t be concerned if a terminal has more than one cable connected to it. It's necessary to construct these kinds of battery banks successfully.

In theory, you can connect as many batteries as you want. But when you start constructing a tangled mess of batteries and cables, it can be very confusing, and confusion can be dangerous. Keep in mind the requirements for your application, and stick to them. Also, use batteries of the same capabilities. Avoid mixing and matching battery sizes wherever possible.

Always remember to be safe and keep track of your connections. If it helps, make a diagram of your battery banks before attempting to construct them. Good luck!

Quick Vocabulary Reference:

AMP Hour is a unit of measure for a battery's electrical storage capacity. A manufacturer will subject the battery to a specific amp draw over a 20 hour timeframe in order to determine the AH capacity. The amp/hr rating can significaly change based on the given load applied for more information see our article: Peukert’s Law | A Nerd’s Attempt to Explain Battery Capacity.

Voltage represents the pressure of electricity. Some applications require more "pressure," meaning higher voltage.

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432 people commented, TECH, Richard North, Mathias Maul, Tech, and 428 others
This article is rated 4.8 out of 5
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  • Richard North
    My deer cameras use 8 AA lithium batteries, and typically all 8 measure 0 or nearly 0 volts when I change them; but sometimes one has the same voltage as when new. How is this possible? Are these batteries worth saving for re-use? If all 8 were in parallel and one made poor contact, this would explain things, but this cannot be the case as the battery pack comprises 4 columns of 2 batteries physically is series end-to-end. (I haven't traced the circuit within the pack, nor have I measured its output voltage, and I plan to do so, but even after I do so my questions will remain.)

    Reply  •  Rated article 4  •  January 1, 2023 at 7:14 am
    • TECH
      While we carry the smaller cell AA or AAA lithiums, we really don't get too involved in testing them. You are correct it shouldn't be possible as the voltage should have declined somewhat from the new. However, I don't have an explanation as to why. Your question is open to the feed should others have insight.

      Reply  •  Rated article 5  •  January 23, 2023 at 1:31 pm
  • Mathias Maul
    How do you change a series-parallel configuration if I’m using 4 12v 7Ah lithium batteries?

    Reply  •  Rated article 5  •  November 28, 2022 at 3:12 pm
    • TECH
      Unfortunately, we do not offer wiring advice in the forum. I would suggest reading the articles and looking over the images as we have provided a similar series parallel example in this article. I would also verify with the lithium manufacturer that you can put them in series and/or parallel. Most of these smaller lithium batteries we find are not approved for series or parallel connections.

      Reply  •  Rated article 5  •  December 13, 2022 at 1:02 pm
  • Sekani
    Which one as the highest running hours? (1) 3000W inverter 24V system, using 4 batteries Of 12V/220Ah each, (24V/440Ah ) series -parallel configuration (2) 3000W inverter 48V system, using 4 batteries of 12V/220ah Each, (48V/220ah ) Series configuration. Note - both inverters are running on same load.

    Reply  •  Rated article 5  •  September 24, 2022 at 10:51 am
    • BatteryStuff Tech
      Sekani, the runtime may be identical, but that will depend on the load applied to the battery. For smaller amp loads, you may see an equal runtime. However, if the load is large, you may see the 48v system react slightly better, as the amperage would be half of that in a 24v system. I would suggest using our Calculator | Determine Run Time for Specific Load.

      Reply  •  Rated article 5  •  September 30, 2022 at 9:57 am
  • Trent Peters
    In 3 battery 36v series is there a battery what works harder than the other batteries?

    Reply  •  Rated article 5  •  August 3, 2022 at 6:13 pm
    • BatteryStuff Tech
      Trent- If you are referring to a battery you can deep cycle more, gel batteries are the best within the lead acid battery category. Gel batteries have an electrolyte that is less reactive so it tolerates deep discharges better than a flooded or AGM battery. In the newer technology category, we have lithium, but it is more expensive and depending on the manufacturer you would need to verify how far the battery can be discharged. For instance, our BSLBATT Lithium Batteries can be discharged fully without causing harm to the battery as they are programmed to shut down at certain voltage thresholds. However, some lithium lines on the market will shut down when they are down to about 30% capacity so it differs from manufacturer to manufacturer.

      Reply  •  Rated article 5  •  August 5, 2022 at 8:17 am
  • Aguanieso
    Is it required to install a 24V battery system when solar panels have 18V to 22V rating? or 18V panels need a 24V solar battery system?

    Reply  •  Rated article 5  •  November 17, 2021 at 4:45 am
    • Mark Mitchell
      Glad I stumbled across this site great stuff!

      Reply  •  Rated article 5  •  September 23, 2022 at 7:59 pm
    • BatteryStuff Tech
      A 24v panel would have an open circuit voltage in the lower 40 volt range with an operating voltage around the 34 volt range. Panels with an open circuit range in the lower 20 volt range with an operating voltage in the 16 to 18 volt range would typically be a 12v panel. Keep in mind that a solar charge controller is recommend as most batteries cannot accept the higher voltages the panels output. In the end you simply need to make sure you are selecting a solar charge controller that can handle your panels voltage range, and keep in mind that you cannot use a 12v panel and push the voltage to output to a 24v battery pack. PWM charge controller will typicaly only output straight across such as a 12v panel to a 12v battery pack, or 24v panel to 24v battery pack. MPPT controllers will typically take higher voltage panel and to the same system voltage or they can down the voltage to a lower voltage battery pack, but they cannot up the voltage of the panel to charge a higher voltage battery pack.

      Reply  •  Rated article 5  •  December 3, 2021 at 10:22 am
    I'm running a 24vdc system on my boat. I have two 8D batts in series for the engine and two group 31 batts in series for the house. I currently have a 12v, 60 amp, 4 bank charger. One output leg from the charger is connected to each battery. Therefore I am getting a 15 amp charge to each pair of batteries. The engine batts get an adequate charge but I find that I have a max load of about 30 amps on the house. I am normally using a generator to power the charger/batteries and the charger is not keeping up with the load. I am considering options and one is to add two more grp 31 batts, which would have to wired in series for 24 vdc and in parallel for additional power as per your drawing? That would provide me with 24 vdc and 200 Ah. Can I use my existing 12v/60amp/4 bank charger to increase my charging amps to 30amp at 24v? How would that be wired? I am considering a new charger at 24v/35 amp but with only one output. How would I connect that to the 4 x 12v series/parallel configuration to achieve 35amp charging? A friend suggested using 4 x 6v batts in series to get 24v/200Ah and getting a new 24v, 50amp charger. I have not found a 24v, 50 amp charger with a 120 vac input but I found one at 24v, 35 amp. Is this a better way to go? thanks

    Reply  •  Rated article 5  •  November 3, 2021 at 6:30 am
    • BatteryStuff Tech
      You would need to inquire with the manufacturer to see if you can put two banks in series to get you your 24 volts. In the end even if you were to put them in series in a series configuration the voltage is going to go up but the amperage is going to stay the same, so it would only be a 24v 15 amp output. In the end I feel this would be a bad idea regardless as most 60 amp chargers have a 500 to 600 AH range if they are air cooled, and realistically only 500 AH if they are of waterproof design. In the end I feel you are simply going to have to start separating banks and going with different chargers for your house and starting banks. You can contact our tech department for further help via our Contact Us page.

      Reply  •  Rated article 5  •  November 3, 2021 at 8:40 am
  • Ray Velez
    I have 10 MK gel 40AH batteries, I would like to use an 3K watt inverter back up on what size wire and what wiring method of wiring should I use, also what size trickle charger would I need for batteries? Thank You

    Reply  •  Rated article 5  •  October 31, 2021 at 12:45 pm
    • BatteryStuff Tech
      The inverter manual should cover the recommended wire size. Typically, most inverter companies include a table that indicates the wire size based on the distance from the inverter to the battery pack. In most situations they recommend a distance of no more than 10 ft but we have seen many limit it to 6ft or less. In the end your inverter manual should have a wire size recommendation. As far as a charger... we do carry plenty of charger converter power-supplies typically used for these type of applications. You can use our contact us page to ask a tech for assistance in selecting a charger. When contacting them please include your intended voltage and total AH in your initial email as that will help them in recommending a charger.

      Reply  •  Rated article 5  •  November 1, 2021 at 8:32 am
  • James Arthur Lugg
    I have 2 six volt AGM batteries in series for the cabin of our Roadtrek that are in the engine compartment and are charged with three solar panels on the 5e roof of our rig. Would there be any advantage with replacing those batteries with two 12 volt LiFePO4 batteries wired in parallel?

    Reply  •  Rated article 5  •  October 9, 2021 at 3:00 pm
    • BatteryStuff Tech
      If these batteries are in the engine compartment you may want to talk with the lithium manufacturer about the location they are stored in. AGM batteries which are considered lead acid batteries are pretty forgiving when it comes to the environment they are charged in, whereas lithium can be not so forgiving. In general lithium batteries tend not to be able to hold under load when subjected to high heat areas. Also, the charging system would most likely need to be replaced with one that is 2-stage meant for lithium. In the end you may get more cycle out of a lithium battery, but the cost is also far greater than a typical lead acid of the same capacity.

      Reply  •  Rated article 5  •  November 1, 2021 at 9:38 am
  • Chris
    I am looking at a 24V lithium system for my trolling motor,. I have planned to purchased two 105A/h lithium battery but have since seen a single 24V battery which would actually save some time and cost in modifications to store the battery's. The physical dimension of the 24V battery is not much more than a 12v battery so I am wondering what I will loose/gain between the two options. I am not an electrics expert, so my brain would think along the lines a 20L bucket(two battery) of water vs a 10L single battery) bucket of water. drill a 3mm hole in each- the water pouring out is equal in each but the 20L bucket will last a lot longer. Am I on the right track with how this compares to the two battery systems mentioned above. Thanks

    Reply  •  Rated article 5  •  October 4, 2021 at 6:42 pm
    • BatteryStuff Tech
      Realistically, it is hard to compare the two types of chemistries in terms of size as lithium is far more compact in terms of storage over a lead acid battery. Often time a lithium battery of similar size has a lot of empty space withing the casing. The only reason battery manufacturers stick to a case size is for fitment purposes as most will not want to change their battery box. If your able to save and the modification still justifies the expense.

      Reply  •  Rated article 5  •  November 1, 2021 at 10:03 am
  • Mauritz
    When I connect batteries in parallel and run it, will it take longer to charge it again?

    Reply  •  Rated article 5  •  September 8, 2021 at 5:20 am
    • BatteryStuff Tech
      When you putting batteries in parallel it increases the capacity of the battery pack, which also increasing the charge time. Because of the increase a new charger may be required at a certain point to avoid burning up the batteries or the charger. We typically recommend selecting a charger that has an amp rating of 10% up to 25% of the battery packs AH rating. Also, keep in mind the manufactures max amp rating typically labeled on the battery as it might be less than the 25% rule. In the end going below 10% can start to overwork the charger resulting in a premature failure, and going above 25% will typically start to boil the battery.

      Reply  •  Rated article 5  •  November 1, 2021 at 11:58 am
  • Chris
    I have a small solar off the grid system with inverter and I initially purchased a 12V deep cycle battery for it, a couple months ago my neighbor offered me (2) fairly new 6V batteries from his camper he happened to get through a warranty issue with the OEM. Can I connect the (2) 6 volt in series, and then parallel into the 12V or are there concerns with combining 6V & 12V batteries together? I thought this would be a cheap way to expand my overall battery storage but want to make sure there aren't any issues I'm not aware of. I would appreciate any feedback you would have. Thanks

    Reply  •  Rated article 5  •  June 15, 2020 at 2:13 pm
    • BatteryStuff Tech
      Unfortunately, it is not recommended to put batteries in parallel or series if they are of different age, type, or chemistry. By doing so you can overcharge a battery within the battery pack and can cause that battery or others to fail.

      Reply  •  Rated article 5  •  June 15, 2020 at 3:06 pm
  • Matt
    Can I wire 2 batteries to my inverter separately

    Reply  •  Rated article 5  •  June 5, 2020 at 3:07 pm
    • BatteryStuff Tech
      It can be done with the proper equipment. Typically need a switch able to handle the load.

      Reply  •  Rated article 5  •  June 15, 2020 at 1:56 pm
  • Nick Miller
    can you hook 2 12 volt batteries in series and parallel with 2 battery on / off switches? obviously with both switch off while changing from series and parallel? im trying to be able to switch from series to parallel with 2 on / off switches(one switch on while the other is locked and off) and only change voltages while both switches are off im trying to run 2 different voltage requirements obviously never at the same time but for depending on what i need be able to change from combined 12 volts to a single 24 volt. and also where would you want to wire in the switch?

    Reply  •  Rated article 5  •  May 31, 2020 at 6:43 pm
    • BatteryStuff Tech
      We are never a fan of wiring through switches, but in certain application it is necessary such as marine applications for emergency purposes. If the batteries are getting used equally and the switch is simply putting them in parallel or series, then the batteries will remain balanced, and we wouldn't foresee and issue arising in such a setup. However, if for instance you are using one battery and not the other in any part of this setup it would not be recommend as you would start to create an imbalance.

      Reply  •  Rated article 5  •  June 15, 2020 at 1:31 pm
  • Frank Taylor
    Can you wire 3 sets of batteries (already wired in series) parallel? 6 x12v batteries to 24v. Will that triple the ah?

    Reply  •  Rated article 5  •  May 30, 2020 at 5:46 am
    • BatteryStuff Tech
      That would be a series parallel connection, and by doing so with three sets you would be multiplying the AH of the first set by 3.

      Reply  •  Rated article 5  •  June 15, 2020 at 1:25 pm
  • Ilyas Nisar Khan
    I have two 12 volts batteries can i join it with different chargers ?

    Reply  •  Rated article 5  •  May 24, 2020 at 10:39 pm
    • BatteryStuff Tech
      If your talking two of the same type of chargers we would recommend you talk to the manufacturer. Not all manufacturers recommend their chargers be put in parallel with the same type of charger, but some do allow it.

      Reply  •  Rated article 5  •  June 15, 2020 at 12:00 pm
  • Saru
    If I have a 36 volt 20 ah battery that has a 1 c-rate and I use a 12 volt step down convertor to make it 12 volt battery am I okay using trolling motor with a max 60 amp draw?

    Reply  •  Rated article 5  •  May 23, 2020 at 4:11 pm
    • BatteryStuff Tech
      Without any conversions adjustments you probably looking at a 20 Amp draw back to your 36v battery pack. In the end your battery pack is probably not going to last to long under that draw as it is only a 20 AH battery pack. If your converter can handle the load it may work for initially, but most likely it is not going to last a long time.

      Reply  •  Rated article 5  •  June 15, 2020 at 11:57 am
  • David Brakefield
    I have a 24 volt battery system on my bass boat for the trolling motor. I started getting a callcium substance building up on the back of the power head. I then noticed small amounts of the same thing speckled (embeded) on the metal jack plate and the face of the on board electronic sonar face plate. A mechanic said the dealer installed the grounding system wrong. What is this called and how is it possible?

    Reply  •  Rated article 5  •  May 21, 2020 at 4:26 pm
    • BatteryStuff Tech
      Corrosion can be caused by the gassing of wet cell batteries. I would suspect that over a grounding issue as I haven't heard of grounding issues causing such a problem.

      Reply  •  Rated article 5  •  June 15, 2020 at 11:35 am
  • Nathan
    Can you explain why it's better to connect loads to opposite batteries in a parallel configuration? If both will still drain mostly equally if loads are connected to the posts on just one of the batteries, what is the advantage of connecting the positive to one battery and negative to the other? Really helpful article, appreciate it.

    Reply  •  Rated article 5  •  May 11, 2020 at 11:44 pm
    • BatteryStuff Tech
      While you can hook to one battery it is better to equalize the load across the battery pack. It is true that connecting to a single battery will cause them to mostly drain equally, but over time an imbalance can occur. So, to limit any sort of imbalance we suggest connecting to the positive at one end of the battery bank, and the negative at the other end of the battery bank.

      Reply  •  Rated article 5  •  May 18, 2020 at 1:12 pm
  • Lore Christensen
    I have 12 volt system system for my off-grid home. The system is comprised of four 12 volt batteries wired in parallel, a charge controller and an inverter. I’m confused which batteries to connect to the charge controller and the inverter. Seems most diagrams don’t include the connection points for BOTH the charging and discharging sources. Thank you.

    Reply  •  Rated article 4  •  May 11, 2020 at 5:19 pm
    • BatteryStuff Tech
      We don't give wire diagram information aside from the examples above, but I can tell you that it is recommended to make your connections so that you equalize the battery pack during charging or discharging. A lot of our customers will utilize the same connection for both charging or discharging. If you system is too large to utilize the same connections I would suggest talking with your supplier or contractor that setup your system.

      Reply  •  Rated article 5  •  May 18, 2020 at 1:43 pm
  • Patrick E Allen
    how many BMS i need for 10 parallel batteries?

    Reply  •  Rated article 5  •  April 19, 2020 at 1:30 pm
    • BatteryStuff Tech
      Questions regarding lithium batteries should be asked of the dealer or manufacturer of the lithium batteries. Some lithium batteries have built in restrictions which differ from manufacturer to manufacturer.

      Reply  •  Rated article 5  •  April 20, 2020 at 9:29 am
  • Patrick E Allen
    i have 10 100ah lithium batteries, to connect to the all in one vicron inverter. do i parallel all 10?

    Reply  •  Rated article 5  •  April 19, 2020 at 1:25 pm
    • BatteryStuff Tech
      I would suggest consulting the dealer you purchased your batteries for the proper setup. Some lithium batteries have built in restrictions, so they would be the best source for your question.

      Reply  •  Rated article 5  •  April 20, 2020 at 9:32 am
  • J.P.
    I am thinking of running two batteries in parallel on my son’s power wheel to increase the run time. If I wanted to install a battery meter gauge would I need two gauges, one for each battery, or just one? If it is just one, would I only use a 6v (using your example above)?

    Reply  •  Rated article 5  •  April 18, 2020 at 6:12 am
    • BatteryStuff Tech
      If you are putting a battery in parallel it is then one battery pack. So, you would only need one gauge, and the gauge would need to be the system voltage of the battery pack. Unfortunately, we don’t carry any 6v battery gauges.

      Reply  •  Rated article 5  •  April 20, 2020 at 9:34 am
  • Jake
    i want to connect a deep cycle battery to my starter battery on my van with a split relay system between, i have a varta 80Ah starter battery, does the deep cycle battery also have to be 80Ah or could it be 70 Ah or a 100Ah deep cycle battery and does it also have to be the same brand?

    Reply  •  Rated article 5  •  April 15, 2020 at 12:46 am
    • BatteryStuff Tech
      As the tutorial indicates you do not want to put batteries together that are not the same age, type, or capacity. So, in a case where someone wants to add a battery for deep cycling in a van they need to do it through a battery isolator. An isolator separates both batteries and ensures the under the hood battery is taken care of first, and it ensures the under the hood battery doesn't get deep cycled. As you appear to be from Germany I would suggest contacting a local European supplier for your battery isolator. In most cases with battery isolators the only thing you need to match is the battery chemistry, but the AH and the age of the battery can be different. We find most will generally need to obtain an AGM battery for both batteries as the deep cycle battery within the cab should be an AGM as they don't vent gas.

      Reply  •  Rated article 5  •  April 16, 2020 at 9:24 am
  • John Orman
    I have 14 6 volt batteries should I run them 12 or 24 volt and how do I hook them up

    Reply  •  Rated article 5  •  April 7, 2020 at 3:18 am
    • TECH
      Realistically, the voltage you select is dependent on your application. If this is for maintenance purpose then in order to do a 24v setup with 6v batteries the number of batteries you have would have to be divisible by 4, so a 12v setup would probably be more beneficial to maintain all the batteries. As far as hooking them up I would suggest reading the article on how to configure them. If you need more assistance I would suggest contacting your local battery dealer for a more in-depth explanation.

      Reply  •  Rated article 5  •  April 7, 2020 at 7:49 am
  • Bryce Ballantyne
    I have a pop top van that will be running 2 deep cycle batteries in parallel. They will be charged via solar with a generator for backup. I will be running an inverter from the batteries with one battery on the positive the other the negative to evenly disperse the power. My question is both my batteries are in battery boxes. Both boxes have 2 Anderson plugs and external terminals. Can I join both in parallel via the external terminals? Also my solar panel is capable of charging both and has 1 Anderson plug. Will it evenly charge if plugged into one box or like the outward power do I need to put positive to one battery and negative to the other.

    Reply  •  Rated article 5  •  April 5, 2020 at 5:43 am
    • BatteryStuff Tech
      As the article indicates we do not recommend putting batteries in parallel that are of different age, type, or chemistry. This also goes for batteries that are the same, but have not been paired together from the beginning. As far as the capabilities for your setup i would suggest contacting the dealer you purchased the equipment from. When dealing with external terminals outside of a battery box you need to verify what amp rating the terminals are rated for, so you simply cannot put them in parallel unless you know the amp loads will stay within the rating of the external terminals. The terminals may have been rated for charging only, so I would suggest verifying before proceeding. Aside from that you would simply be creating on battery versus two. As far as charging equally we recommend connecting to a positive at one end of the battery pack and a negative on the other end of the battery pack.

      Reply  •  Rated article 5  •  April 6, 2020 at 2:20 pm
  • Nate
    With a series-parallel, would it be beneficial to still go from + of B1 to - of B3 and - of B2 to positive B4? Or is that just best practice for a connecting a load.

    Reply  •  Rated article 5  •  April 4, 2020 at 6:56 pm
    • BatteryStuff Tech
      As we are not an installation center we try to stay away from wiring advise beyond our articles. My best recommendation is you want to keep the battery pack balanced, which would require connecting to a positive at one end of the battery pack, and then the negative at the other end of the battery pack. If you need further explanation then I would suggest contacting our tech department over the phone.

      Reply  •  Rated article 5  •  April 6, 2020 at 11:07 am
    I have a bus and it have a 12 v battery .if i connect one more 12 v battery in parallel to increase the storage, Will it damage the wiring or alternator of the vehicle?

    Reply  •  Rated article 5  •  March 23, 2020 at 8:04 pm
    • TECH
      Existing wiring should be rated for the current setup. Adding an extra battery to an existing isn't recommend unless the batteries are of the same age and type. In that case you should use the same size wire if the batteries are right next to each other. Either way your system should have a starting battery bank and a deep cycle bank. You do not want to add an additional battery to starting battery if you are thinking about deep cycling the battery. The starting battery should only be used for starting purposes and should always be isolated from the deep cycle bank, otherwise you risk damaging the starting battery as they are not meant for deep cycle purposes. If you are looking to add a deep cycle battery for storage purposes the proper way to add an auxiliary battery is through a battery isolator. Battery Isolators make sure the starting battery is taken care of first, and then once the starting battery is charged it switches to the auxiliary battery bank. When sizing the cable I would recommend following the battery isolator's instructions as they will generally have a chart covering the proper size cable given the distance to the auxiliary battery bank. If your isolator doesn't have a chart then you should contact your battery isolator's manufacturer. The Isolators we carry all have recommend cable sizes in their manuals, but every product is different and you should follow your manufacturers guidelines.

      Reply  •  Rated article 5  •  March 24, 2020 at 12:15 pm
  • Kirl Raphael
    Very useful information.. thanx alot

    Reply  •  Rated article 5  •  March 5, 2020 at 10:07 am
  • Bandura
    I need to use a battery to power a 48v 1800w motor for a project. The motor has a rated current of 33A. What will that mean for the battery? I have found a battery that has maximum output of 10A. What does that mean? Does it mean the motor won't receive enough power, or will the motor be fine and still work to 1800w. The controller for the motor also has a current of 38A, so does it mean it's the max it can withstand, or the amount it works at? with all this information, what would you recommend i use as a battery?

    Reply  •  Rated article 5  •  March 2, 2020 at 4:24 am
    • TECH
      If you looking at a lithium battery they will typically have a max discharge rate, which in this case may be 10 A. We mainly deal with lead acid batteries, so in a situation like this we would recommend 4 x 12v batteries. In order to size your battery pack I would recommend using our Calculator | Determine Run Time for Specific Load. In short you need a battery that can withstand your current draw for the time you intend to run the motor, and not discharge your battery pack more than 50%. As far as amp ratings are concerned your best bet is to contact the manufacturer of the equipment. If I was to guess... I would assume your controller can most likely handle a motor with an amp rating up to 38 Amps, but 33 amps is the actual rating for your motor. But, in the end it is best to ask the manufacturer as you don't want to purchase the batteries to find they don't work.

      Reply  •  Rated article 5  •  March 6, 2020 at 8:53 am
  • Anthony
    HELP! I have a stand alone 24v solar gate set-up (no access to mains power) My 2 x 12v 7.2Ah batteries don't seem to hold enough charge over night. They're charged by 1 x 20w Solar Panel. First time use in the morning has the Voltage at around 21-22v which wont even power on the gate circuit board yet alone open/close the gates (this is according to the display on my 24v, 10amp Solar Controller) What should I do here? Wire 4 x 12v 7.2Ah bats in a join series/parallel set-up to produce 10amp 24v output? Increase the Solar Panel size? Or do both??!!

    Reply  •  Rated article 5  •  December 8, 2019 at 4:53 pm
    • BatteryStuff Tech
      Ideally, your 24 hr solar output should be at minimum double your daily draw. For high use gates we see people collecting 3-4 days of energy in a single day. They do this so they can backup energy for bad solar days. In the end you need to determine how many amps you are pulling out of the batteries each day on an average use scenario. Then you need to create a backup to store that energy, another words a higher capacity battery pack. In the end you need to determine how many days you want to backup, and how many days your solar needs to collect on a good day. Simply, upgrading the panel doesn't necessarily get you more run-time unless you increase your battery capacity. While we don't design systems, we do have an article called Solar Systems the Right Way that might help you in designing your system.

      Reply  •  Rated article 5  •  December 13, 2019 at 6:56 am
  • Michael
    I am installing a 12v deepcycle battery with an inverter to my truck. I have a Multi Battery Isolator for it. And I'm using the charging wire that goes to my battery in the truck for the isolator. Should I ground the deepcycle to the frame or will a body ground work? And is this the right way to do it with the truck alternator charging both?

    Reply  •  Rated article 5  •  December 5, 2019 at 4:57 pm
    • BatteryStuff Tech
      I would suggest talking to an automotive tech or the manufacturer of the isolator. Either would be the best source for installation advise regarding the battery isolator. I know in some vehicles there are ground points within the body put in by the manufacturer, but we typically see these for vehicles that are meant to carry an auxiliary battery. If no ground point is available then I would suggest talking to isolator manufacturer or an automotive tech regarding installation.

      Reply  •  Rated article 5  •  December 13, 2019 at 9:37 am
  • Levi
    After reading this it seems that parallel is a better way to go when you want longer run times. I.E. I have a houseboat and was running one 12v deep cycle battery for the interior lights. I was told to buy two 6v batteries and run them in series for longer run times. If I’m reading this correctly, that is not the case. I would be better off running two parallel 12v batteries for more AH. These batteries are separate from my starting batteries and only run the 12v lights, radio, power to propane igniter on fridge and hot water tank. Is that correct?

    Reply  •  Rated article 5  •  December 2, 2019 at 4:39 pm
    • BatteryStuff Tech
      Levi, while putting batteries in parallel does increase AH capacity it doesn't mean you cannot accomplish a high AH battery pack using the series method. In high use applications such as RV's, boats, and home solar applications a lot of people use 6v batteries over 12v batteries. Often times a 6v golf cart batteries are a prime example of similar capacities for in RV and some boat applications and will typically equal the same capacity of a 12v battery put in parallel. The benefit to the 6v battery is the cells are thicker, so they will generally have a longer cycle life, which is a benefit to high use applications.

      Reply  •  Rated article 5  •  December 3, 2019 at 9:51 am
  • Steve Kohn
    Wonderfully clear explanation. Many thanks.

    Reply  •  Rated article 5  •  May 14, 2019 at 1:47 pm
  • Readone
    Thanks very so much it helps me alot

    Reply  •  Rated article 5  •  May 8, 2019 at 12:42 pm
  • Vickie
    Thank you! This is just what I needed to know to set up the battery bank in my RV. The batteries were gone and no schematic.

    Reply  •  Rated article 5  •  October 17, 2018 at 8:57 am
  • CampRicco
    I have two battery banks. One stationary (12v/140ah) and one portable (12v/25ah). I want to be able to plug portable bank into stationary bank for charging. Should I be concerned about the inrush current when connecting portable bank into stationary bank while battery charges are equalizing. Can a resistor be added to cable to slow current while banks are equalizing. If so where in connection and what value would you recommend.

    Reply  •  Rated article 5  •  June 22, 2016 at 9:15 am
    • BatteryStuff Tech
      You do not want to mix and match battery types for charging. The two battery packs you have are of different capacity, so you are creating a situation where batteries are going to get overcharged. I would recommend charging them separately.

      Reply  •  January 18, 2017 at 8:55 am
  • Jim K
    Good morning, I have 2 batteries connected together to make 24 volts for my trolling motor.My question is can I use 1 battery for my outboard for a 12 volt starting and charging system without disconnecting the 2 batteries. thanks for any response jim

    Reply  •  June 18, 2016 at 4:25 am
    • BatteryStuff Tech
      It really wouldn’t be recommend, as you would start to unbalance the battery pack, which could later result in a battery getting overcharged. If this happens too often the battery could fail and bring down the whole pack.

      Reply  •  January 17, 2017 at 11:56 am
  • Daniel Mangiardi
    You guys are awesome! Thanks for all the info. Tech and Jeremy Fear have thoroughly answered a lot of great questions. They should be promoted and given a raise. Seriously. This kind of customer service earns business and demonstrates professional prowess. Again, thanks for all of your help! One can learn a great deal perusing some of the questions and solutions in this thread. Sincerely, Your Future Customer

    Reply  •  Rated article 5  •  June 17, 2016 at 10:22 pm
  • Adam
    I have 6 1.75 v lead batteries that I got from a electric plant that is being torn down how would I wire them up to produce 12v or 24v

    Reply  •  June 15, 2016 at 6:12 am
    • BatteryStuff Tech
      Assuming they are 2 volt cells currently sitting at 1.75v then it would be possible to make a 12v battery pack in series, as long as the batteries will charge up.

      It is the same method as you see above in the article… negative terminal of the first battery to the positive terminal of the second battery, and then continue with the negative terminal on the second battery to the positive terminal on the third battery, and so on till you complete the string…

      Reply  •  January 17, 2017 at 11:13 am
  • Mike
    Could I set up another 4 12volts 20 ah battery in my 48v but make them parallel to my 4 existing batterys would that keep it at 48?

    Reply  •  June 9, 2016 at 9:41 am
    • BatteryStuff Tech
      It is not recommended to mix and match battery of different type, age, or capacity. So even though you could do it, we would not recommend such action. We only recommend connecting batteries that are all the same age, type, capacity, and put together to begin with.

      Reply  •  January 17, 2017 at 10:08 am
  • Jerry Hamilton
    I have 4 identical 8 volt batteries can I use all 4 in a 24 volt system? I was thinking that I can put 2 batteries in parallel and put it in series with the other 2 and get 24 volts. 8 V series (8 v parallel 8 v) series 8 volt. It should equal 24 volts but I’m not sure what it would do to battery life and charging. Has any one tried this?

    Reply  •  Rated article 3  •  June 8, 2016 at 1:37 pm
    • BatteryStuff Tech
      The only way I can see using 8 volt batteries in series to equal a 24v system is tying 3 of them together in series, which will leave you with one battery you cannot use. Batteries in series or parallel are only recommend to be the same type, so three 8V batteries are required for 24v system, and if you wanted a series parallel setup for higher capacity you could get another 3 to put in parallel.

      Reply  •  Rated article 5  •  June 9, 2016 at 12:02 pm
  • Marcus
    Hi There, I have bought a 30 year old boat that has two banks of three 12v 75Ah batteries, two are connected in series and one in parallel. The system is 24v so I understand that this is being achieved by the two in series.I realise that this is a very bad set up and I should have four batteries with two banks connected in series and then joined in parallel (something I will be updating). However I seem to have an extra problem, when left with the main breaker switch off the two connected in series slowly loose their charge. Is this due to the bad setup or is it likely to be a drain somewhere? I would have thought that if any of them were to drain it would be the one in parallel. Any advice would be greatly appreciated.

    Reply  •  May 26, 2016 at 3:54 am
    • BatteryStuff Tech
      If you main breaker is off I would either suspect there is a draw coming off the battery before the breaker, or the batteries might be naturally discharging faster because they are at the end of their life. If each bank is isolated I can’t see the 24v system being drawn down by the 12v system. I first suggest disconnecting them from the system and see if they discharge on their own. If not, then I would suggest tracking down the parasite draw.

      Reply  •  Rated article 5  •  June 9, 2016 at 10:00 am
  • James Cook
    All of this makes my brain hurt. Here’s what I’m trying to do. I have a RV with two 12v 100 amp batteries, giving me only 200 amp hours to run the RV. I want to remove them and add eight lithium 12v 100 amp batteries, to increase my battery bank to 800 amp hours, and I also plan to add solar charging so I don’t have to run the generator so often. How should I wire these batteries together?

    Reply  •  May 23, 2016 at 9:18 am
    • BatteryStuff Tech
      Assuming your RV house bank is a 12v system your new battery pack containing 12v batteries will be wired together in a parallel setup. In regards to Solar make sure you get a solar charge controller that is designed for Lithium, and then your solar panels go to the batteries through the solar charge controller. That is how most hook up their systems, but there are more complex system out there that can run the solar through an inverter chargers so solar power is primary over battery power. Obliviously if your getting into an advance setup we recommend contacting the manufacturer of the equipment you are purchasing for proper installation recommendation.

      Reply  •  Rated article 5  •  May 26, 2016 at 12:52 pm
  • Matt
    Can you please help solve this mystery fot us? Our cabin has one 24v 100A panel with mppt charger.
    We have 2 × 105Ahr batteries, less than a year old. Thinking of adding a 3rd due to them draining quickly from the refrigerator turning on and off all day.
    Is a 3rd battery going to be ok on the system? We are only here couple times a month so we don’t care how long they take to charge.
    Thank you!

    Reply  •  Rated article 5  •  May 22, 2016 at 4:48 am
    • BatteryStuff Tech
      Simply adding more capacity might help you in bad weather days, but if your having issues and it is not during bad weather days you will most likely end up with the same results. In general your solar system at minimum should be putting double your daily draw back to the batteries to make up for bad weather days. Your controller will take care of the excess if they are already fully charged. In regards to adding another battery into an older bank… It is not advised. The newer battery will fully charge at a faster rate than the other batteries. In the end it will most likely get overcharged as the system tries to fully charge the older batteries. This will cause the new battery to fail over time, and could eventually bring down the whole battery pack.

      Reply  •  Rated article 5  •  May 26, 2016 at 7:54 am
  • Scott
    I purchased a rare vehicle that requires 24V to the engine but the other electronics are 12V. It has two identical rather new 12V batts in series and after sitting a few weeks went dead.

    I removed the leads to charge each batt separately with my 12V charger. When first testing each one with a volt meter one had a normal polarity and 12V, the second batt had 10V and reversed polarity coming from the posts. Is this because the second batt is failing, is it normal to have a reverse polarity memory on the batt with positive to the neg post? Or if both batts are perfect should the second batts have normal polarity on the charge? Thank you in advance.

    Reply  •  May 19, 2016 at 10:40 am
    • BatteryStuff Tech
      The batteries that is at 10v most likely has a bad cell in it. In regards to why the polarity has reversed it is often caused when the battery is fully discharged, and then charged back up in reverse. Another words if you accidental hooked the positive to the negative, and the negative to the positive, you can end up reversing the polarity if the battery was completely discharged. A suggestion to keep both batteries balanced would be to use a 24 volt maintainer, and a 24V to 12V DC to DC Converter. This will keep both batteries balanced, and your 24v battery pack maintained.

      Reply  •  Rated article 5  •  May 26, 2016 at 9:13 am
  • Jason
    I am trying to run my camper off solar. I have calculated 600w per hour at max, 70A per hr at 5 hrs. I have currently 2 12V batteries in parallel with 70ah’s. I have The harbor freight 45w solar panels, and a 1500w continuous inverter I have read article after article and I just can’t figure out exactly what I need to do. Please help me. And thanks

    Reply  •  May 16, 2016 at 4:47 pm
    • BatteryStuff Tech
      Jason I wish I had good news for you, but your watt draw well exceeds your harbor freight panel. As you can see your requiring 600 watts an hour, but your panel only puts out 45 watts an hour. In most cases when you have a draw of that size an RV would switch over to their generator to power such devices. Any good solar setup will at minimum put double the daily amp draw back to the battery pack, and most will store up a extra day at minimum of energy. I would suggest reading our article Solar Systems the Right Way.

      Reply  •  May 19, 2016 at 12:25 pm
  • Mike
    I am going on a family vacation with a bunch of family members. I have four batteries that I wanted to connect together and use an inverter so that I have Outlets for people to charge their phones. How should I wire them up series or parallel or series parallel? I wanted to hook them up to my car battery so that I can charge them at some point during the day. Which way would last the longest without causing harm to my batteries?

    Reply  •  Rated article 5  •  April 20, 2016 at 6:57 am
    • BatteryStuff Tech
      It depends on your system voltage and the voltage of the batteries. If you have 12 volt batteries, and your inverter is 12 volts, then you hook them up in parallel. If you have four 6 volt batteries and your inverter is 12 volts then it is a series parallel hookup. As far as charging the batteries I would not suggest hooking them up to your car battery for charging, as you could damage your car battery by the alternator overcharging it. The proper way to charge an additional battery pack off an alternator would be to use a Battery Isolator, such as our Quick Power 120 Amp Battery Isolator Bi303303. If you have any specific technical questions you may contact us via our TECH Help Form.

      Reply  •  Rated article 5  •  April 20, 2016 at 9:04 am
  • Olugbenga
    Hello Tech,
    I have a battery of 12v,200amp that lasted for 4-6hrs with a 0.5kva inverter, I got an extra battery connected it IN parallel but not a difference in output after achieving 12v,400amp. I thought I’ll get more back up hours what could be the problem.

    Reply  •  April 16, 2016 at 8:43 pm
    • BatteryStuff Tech
      I would suggest using our Calculator | AC to DC amperage conversion run through an Inverter. Ideally you don’t want to discharge your battery more than 50% of its capacity. Also if your are pulling very high amp loads the battery bank you have might not be sufficient for your load depending on the low voltage cutoff on your inverter.

      Reply  •  Rated article 5  •  April 18, 2016 at 10:05 am
  • Rob
    Wow I do not know how you’ve done this! It seems like a huge time investment and I REALLY appreciate your dedication. Kudos are not enough. Thank you for this….especially the truly weird and wonderful people asking the same questions multiple times. Your tech staff must have some wonderful discussions at break time. See the internet can be amazing at times. I bow and salute experts that really are experts. Refreshing. Rob H

    Reply  •  April 14, 2016 at 7:54 am
  • Saby
    ls…help me…can a 2v , 300Ah battery be replaced
    with a 2V, 200 Ah battery for a 24V, 300 Ah capacity battery bank?

    Reply  •  April 11, 2016 at 7:45 am
    • BatteryStuff Tech
      Sure, you can go up in Amp/Hr or down, however your capacity does change so you should re-calculate your need. Also Please be clear that i’m not saying you can replace a single battery in a pack with a different AH rated battery. When you go to replace your entire pack you can change capacity to fit your needs.

      Reply  •  Rated article 5  •  April 11, 2016 at 11:20 am
  • Owais
    Dear fellow, i have a simple query but a lot of confusion. I have two 12 v batteries (250 and 200AH) connected in series to a 24 V solar inverter. M not happy with its charging and output. I thought that might be the different amperage is the problem, and after viewing this article my confusion increased. So plz plz plz tell me what should i do, so tht i can save my valuable batteries and inverter. Thanx

    Reply  •  Rated article 5  •  March 18, 2016 at 11:45 am
  • Pete
    I have a 800VA inverter, with one 12v 200amp battery. I just bought four 12v 100amp battery. Cant I connect all 5 batteries to give a 12V 600amps???

    Reply  •  December 11, 2014 at 5:32 pm
    • BatteryStuff Tech
      It is never recommend to mix and match different battery chemistry, types, and size.

      Reply  •  Rated article 5  •  January 2, 2015 at 1:45 pm
  • Dave Smith
    I want to power a freezer at a research station in a fairly remote part of India. The freezer draws 4.5 amps at 115 volts. Grid power is intermittent and I plan to use a diesel generator for most of the off-grid power, but as the samples in the freezer cannot be allowed to defrost, I want to have a battery back-up system in case of fuel shortages, breakdowns, etc. Does it make sense to use a bank of 12v batteries through a 1500 watt inverter to power the freezer? If I connect a charger to the grid and then to the batteries, would the charger have to be disconnected when the batteries were being used? I could use a manual switch to go from the generator to the batteries. Sorry but I haven’t figured out the amp/hour thing for sure. How many amp/hours would I need to operate the freezer for, say, four hours? 115/12 × 4.5 × 4 = 173? With some extra added for inefficiency, starting, etc. so say 220?

    Thank you for this very valuable service.

    Reply  •  December 9, 2014 at 4:24 pm
    • BatteryStuff Tech
      We would require more information about your situation. Please contact Tech Support.

      Reply  •  Rated article 5  •  January 2, 2015 at 1:25 pm
  • Biron
    i have a 24v system am using two 12v batteries connected in series but i notice one of the batteries discharging faster than the other what is the cause of this problem and how will i amend it

    Reply  •  December 7, 2014 at 12:59 am
  • Moe
    Need some input please…I’m a truck driver and my truck is currently running 4 12v batteries in parallel. I wanna add 4 more batteries to the circuit of 12v each to increase amperage. All 8 batteries are the same. I’m aware that voltage will remain the same if all 8 hooked up in parallel and amperage will double. Question; will the increased amperage hurt any of the components in my truck, or is the extra amperage just being stored for easier engine starts and longer running components (like fridge, microwave laptop,…) without idling the engine?

    Reply  •  Rated article 5  •  November 27, 2014 at 12:09 pm
    • BatteryStuff Tech
      As always you want to follow manufacturer suggestion. In general simply adding more batteries in parallel just give you more capacity, and the voltage stays the same so there shouldn’t be any issues.

      Reply  •  Rated article 5  •  December 29, 2014 at 12:39 pm
  • Kevin
    I have 1 × 12v 120a/h AGM Battery and 1 × 12v 94a/h AGM battery in my caravan that I wish to connect in parallel.
    I will be using a DC-DC C-tek charger or AC-DC C-tek charger depending on where I am.
    What issues will I face charging these batteries together when connected in parallel because of the different capacity ratings?

    Reply  •  Rated article 5  •  November 25, 2014 at 3:45 pm
    • BatteryStuff Tech
      The smaller capacity battery can become overcharged, and could fail bringing down the whole pack.

      Reply  •  Rated article 5  •  December 29, 2014 at 12:43 pm
  • Chidi
    Hi, I have 1.5KVA Inverter four 12v batteries. I want to increase the output voltage of the batteries to 24v(which is what is required as the input of the inverter) and also triple the Amp-hours so that my power output will last longer. I was thinking, can I connect two of the batteries in parallel thus doubling the amp-hour and keeping the voltage constant AND then connecting connecting them in parallel to the remaining two batteries which are connected in series. The output that enters the inverter now comes from the terminals of the batteries that are connected in series. will that give me my desired output?

    Reply  •  Rated article 5  •  November 19, 2014 at 3:27 am
    • BatteryStuff Tech
      It would be a similar hookup to our example in the article: Batteries Joined in Series and Parallel. The only difference is that you are using 12 volt batteries and the voltage would increase to 24 volts versus 12 volts as the example shows with the 6 volt batteries.

      Reply  •  Rated article 5  •  November 19, 2014 at 3:04 pm
  • Nat
    Hoping this is a simple question. I’m a trucker and my rig has 4 12v batteries configured to operate at 24v. I was given a 12v, 5000w inverter(overkill for my needs but free is free) and wish to install it properly. I believed I had everything I needed but was concerned about the fact that the inverter is 12v while the battery bank is 24v. I assumed it would be fine just to connect to one of the batteries but read above that doing so can reduce the longevity of the entire bank. However another post mentioned a 24v to 12v step down converter. What do I need to look for to purchase the proper converter for my system?

    Reply  •  November 18, 2014 at 12:38 am
    • BatteryStuff Tech
      It is never recommended to draw off a single battery in a pack as it can unbalance the pack. I would would recommend contacting our Tech Department for suggestions.

      Reply  •  Rated article 5  •  November 19, 2014 at 2:39 pm
  • Michael Dawson
    I have 36, 2 volt batteries, wired to give me 12 volts for my home solar system. My 12 volt inverter just died and my new inverter is 24 volts. What is the best way to wire my bank to give me 24 volts. Thanks so much.


    Reply  •  November 16, 2014 at 5:11 pm
    • BatteryStuff Tech
      It would basically be three strings of 12 batteries in a series parallel hookup.

      Reply  •  Rated article 5  •  November 19, 2014 at 2:34 pm
  • James
    Hi – I’ve got a small bank of 3 12v (total 300ah) batteries in parallel to provide lighting and some other power for small electrical devices (via a 240v inverter) for when we the power is out – they are kept on a trickle charger all the time at 100%. We had a power outage today for about an hour, I was only running 2 low voltage lights for combined draw of about 25 watts for about 60 minutes (0.1 amps at 240v), When the power came back on I hooked up the charger and it said the battery bank was “Low” the voltage reading was 12.4v when I started it charging again. Is this right, even with the (in)efficiency of the inverter factored in, by my reckoning I should only have used about 3ah of bank’s capacity?

    Reply  •  November 10, 2014 at 3:02 pm
    • BatteryStuff Tech
      I figured roughly 4.6 AH, but I believe your batteries may have been in discharged state prior to the power outage. Either that or they are on their way out.

      Reply  •  Rated article 5  •  November 19, 2014 at 12:43 pm
  • Joseph
    I have a question. I have two 3.7v 2500 mAh LiPo batteries that I want to run in series. Can I use a 1A 5v usb charger to charge these batteries while they are in series?

    Reply  •  November 9, 2014 at 8:58 pm
    • BatteryStuff Tech
      Two of those batteries in series equals 7.4v, so unless your USB device is designed to charge that system voltage I would not recommend it.

      Reply  •  Rated article 5  •  November 19, 2014 at 12:04 pm
  • Paul Croft
    I have 4 X 115ah 12v batteries if I connect them as 2 banks of 2 connected in parallel will I have 460ah and 12v

    Regards Paul

    Reply  •  October 31, 2014 at 5:09 pm
    • BatteryStuff Tech
      If you connect them together without a switch to select between them then it is really one bank, and yes you would 460AH.

      Reply  •  Rated article 5  •  November 19, 2014 at 10:40 am
  • Dell
    Inherited 18 Kyocera 50 watt panels but they were wired for 24-volt system. Rewired them for 12 volt system and have 8 new 6v golf cart batteries (deep cycle) from Sams. Concern is Centech 2000 constant 4000 peak inverter from Harbor Tools states in directions NOT to use batteries in series. Is this just an overprecaution? Can I wire two banks of 4 in series and connect to + and – terminals on each end with inverter terminals? Need to power a 5th wheeler at night and air compressor for air tools during day and two deep freezers. Also, are 30 amp fuses/shut offs between panels and Trace controller and between Trace controller and battery bank and battery bank and inverter sufficient? Thanks

    Reply  •  October 31, 2014 at 1:09 am
    • BatteryStuff Tech
      I would recommend talking to the manufacturer in regards to your question about connecting the batteries in series. I’m sure they have a reason for it and maybe they can explain it to you, and then you can choose to proceed. Two banks of 4 6v batteries in series would give you a series parallel 24v system. In general the manufacturer will recommend a fuse to use based on the size of the inverter, so I would look for their recommendation. We do sell inverter installation kits and depending on the one chosen it will come with a 150A or a 200A fuse based on the size of the inverter.

      Reply  •  Rated article 5  •  November 19, 2014 at 8:59 am
  • Ninh
    I have two 12V batteries in parallel. If I want to “manually” isolate one battery (used for accessories) from the main battery (used to start car) when the engine stops running. What do you have to do this task and when should I install the isolator? I ready about some automatic isolators (solenoid type) that I do not want to get involvaed with and is looking for something manual and simnple.

    Reply  •  October 16, 2014 at 1:13 pm
    • BatteryStuff Tech
      In general if you want accessories to run on a different battery then they have to be wired to that battery directly. You question goes beyond our expertise here, I would suggest talking with a local mechanic for suggestions. The battery isolator we sell are designed to charge the hood battery, and then send any extra amperage to the backup battery.

      Reply  •  Rated article 5  •  November 18, 2014 at 11:35 am
  • Scott
    Hello… Love the site! I have 2 2volt deep cell golf cart batteries (one Trojan, one Interstate) I used in my previous rv. We just bought a new rv and it has one 12 marine/rv battery in it. Can I connect my 2 6 volt and the 12 volt for an overall 12 volt output? If so who is this accomplished?

    Thank you

    Reply  •  Rated article 5  •  October 12, 2014 at 2:12 pm
    • BatteryStuff Tech
      It is never recommend to mix and match different battery types. When creating a bank you want to make sure the batteries are of the same age, chemistry, and type. When you mix and match batteries outside of this recommendation there is a risk of damaging a battery pack.

      Reply  •  Rated article 5  •  November 18, 2014 at 9:54 am
  • Aene
    i have 3, 12v batteries that have 7ah for each (sealed lead acid battery).
    i have a charger that is rated for 12v batteries 20ah-80ah.
    im using the 3 batteries in parallel, and that gives me 21ah.
    can i charge them with this charger???
    or it will cause them to blow.

    Reply  •  Rated article 5  •  October 10, 2014 at 5:33 am
    • BatteryStuff Tech
      As long as your charging them as a pack with a total of 21AH then you would be fine using that charger.

      Reply  •  Rated article 5  •  November 18, 2014 at 8:08 am
  • Ray
    I recently was given a 40 battery bank of Monolite 6 volt sla 100 amp hour batteries, connected in series/parallel to create 12 volts. I only want to use this for storage incase of a power failure. My question is, what type/capacity of charge controller should I use to keep them topped off? I would be using grid power for this, but would like to eventually like to switch to wind/solar in the future.

    Reply  •  October 7, 2014 at 11:00 am
    • BatteryStuff Tech
      The charge controller is rated to handle the incoming amp load to charge the batteries. When selecting one you just want to make sure that it exceeds the amp rating that is charging the batteries.

      Reply  •  November 17, 2014 at 2:14 pm
  • JB
    Looking for proof of concept validation before I start cutting and crimping cables:

    System will consist of 3 banks of: 4, 12v, 40 Ah LifePO4 Lithium batteries in series for a 48v, 40 Ah bank; all banks will then be run in parallel to bring amp-hours up to 120 Ah at 48v.

    To charge the system, I will attach a 48v, 25 amp charger to the central, end lead. Charger and batteries are BMS controlled.

    System powers a 3.5 KW electric drive aboard a small sailboat.

    Main concers, other than sinking to boat of course is; will this work? Where should I add the fuse(s) (at the end of each bank (150 AMP?) or one at the very end (200AMP?))?

    Total novice and dangerously not as intimidated as I think I should be…


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

    Reply  •  Rated article 5  •  October 5, 2014 at 10:00 am
  • Xlr8
    I have a sailboat and want to put in a 600amp battery bank for domestic use.
    My diesel motor has a 65amp alternator.

    What would you use to put this together? 6v or 12v batteries? what type?

    What is the best I can do?

    Reply  •  September 7, 2014 at 8:54 pm
    • Admin
      Due to the fact that we don’t have all the information for your system we would need you to contact us at so that we can ask the appropriate questions, to get you the answer that you may need.

      Reply  •  Rated article 5  •  September 12, 2014 at 2:08 pm
  • Dabke
    one 1 kva 96 v dc/230 v ac UPS having 8 nos 12 v 28 ah batteries. can we add more eight batteries to achieve more ah capacity by series parallel combination ? can this UPS do the proper charging to batteries?

    Reply  •  Rated article 4  •  September 7, 2014 at 3:28 am
    • TECH
      We never recommend mixing and matching batteries that are different ages, type, or chemistry. With that in mind, if you are considering replacing the whole pack and going to a larger pack with more capacity you want to be sure your charger is about 10% of the amp/hr of your battery back for an effective charger. Going smaller than 10% will start to work the charger more, and could eventually overwork the charger to its death. We also never recommend getting a charger that has an amp rating that would exceed 25% of the battery packs amp/hr rating, as it would most likely overheat the batteries, and in turn causing possible damage.

      Reply  •  Rated article 5  •  September 25, 2014 at 10:00 am
  • CB
    Hi there,

    I am a beginner in this kind of thing, so this might be a really simple question.

    Does the voltage of the battery need to match the voltage of the motor?

    For example, could I use 2 12 volt batteries connected in series with a 36 volt 750 watt motor?

    Or would I need 36 volts of battery (3 12 volt batteries) to power a 36 volt motor?


    Reply  •  Rated article 5  •  September 4, 2014 at 9:00 pm
    • BatteryStuff Tech
      Your battery voltage needs to match your system voltage.

      Reply  •  Rated article 5  •  September 12, 2014 at 12:59 pm
  • Mike
    Thanks for all the great info that is difficult to find elsewhere! I have a 6000w inverter-powered cabin with two separate battery banks, and one bank appears to need charging more than the other. One bank is 4 12v batteries, the other is 3 12v: it used to be four also but I found one bad one last year and removed it. Do you see a problem here? Thanks

    Reply  •  Rated article 5  •  August 31, 2014 at 7:03 am
    • BatteryStuff Tech
      As long as each bank is isolated from each other, and your charger is not going to have an issue charging a smaller amp/hr battery bank, then you should be fine. Just keep in mind that you still don’t want to discharge any bank more than 50% or your risk effecting the life of your battery, so the smaller bank you will not be able to pull from as long.

      Reply  •  September 12, 2014 at 11:16 am
  • Camper
    Is “2 6volt batteries in series” basically the same as a 12v battery? Can I run a generator the same as I would a regular 12v system? Looking at getting a new camp trailer but am not familiar with the battery config.

    Reply  •  August 26, 2014 at 1:25 pm
    • BatteryStuff Tech
      2 6v batteries in series will provide you with 12 volt, which can be used in place of a single like sized 12v battery.

      Reply  •  August 27, 2014 at 12:08 pm
  • Giri Manzini
    This article successfully answered my question about the parallel battery connection. but i still have a question. 1 have two 12v batteries which i have installed in parallel. i connected the plus and the minus of the #1 battery to the plus and the minus of the #2 battery. i also connected the #1 battery to the solar charge controller. so, can i connect the #2 battery to the inverter? or do i have to charge it to battery #1 too?

    Reply  •  August 19, 2014 at 12:38 am
    • Admin
      Please email your question, along with a schematic, to

      Reply  •  August 20, 2014 at 7:34 am
  • Admin
    Due to the fact that we don’t have all the information for your system we would need you to contact us at so that we can ask the appropriate questions, to get you the answer that you may need.

    Reply  •  August 15, 2014 at 2:20 pm
  • Rabbe
    i need 2 pcs battery for my machine 12v 2.9Ah but i cannot find those in my country.
    is there any other option to chose different battery and that will give me same output.
    what is that value of battery plz inform me its urgent.

    Thanking You

    Reply  •  August 14, 2014 at 4:18 am
  • Jim
    Hello and thank you for the excellent article/site. I have a floor machine with four 6 volt batteries wired in series to provide 24 volts. I am attempting to change out 2 of the batteries. I have disconnected the interconnect cables from the old batteries, but I am now getting an arc when I attempt to make the final connection between the batteries. The lead connector from the batteries to the motor is disconnected. Do I need to have the lead connected to avoid this situation or is there something else I can do to avoid arc when making the final connection (maybe discharge the batteries, etc)? Thanks.

    Reply  •  Rated article 5  •  August 13, 2014 at 6:20 pm
  • F-Alli
    I have been following up with this thread for a sometime , and i have been enjoying the questions and their corresponding answers.
    Pls i have two questions-

    1- I have 4 12/150AH batteries , connected in series -parallel, on a 2.4KVA /24V rated inverter .
    Please show me how i can calculate the duration it would last if i have an average load of 1000W .

    2- How can i integrate a Solar Panel to it the Inverter, to automatically charge the batteries when there is no Public Electricity ?


    Reply  •  August 12, 2014 at 5:27 am
  • Joshua M.
    i have 3 12 volt batteries in my car. in front i have a optima red top and the trunk 2 ac delco. i just installed a 400 amp alternator which works when i clamp it or put it under load. but my voltage at idle is at 12.90 and when i rev pass 1000rpms it will go up to 14.9 where i set it. i was wondering if because i have two old batteries in the back and one new in the front if the will be a reason my alternator is reading 12.90 at idle. is it possible because that the batteries in the back are weak and cause a low reading?

    Reply  •  August 9, 2014 at 6:46 am
  • Fern
    What would happen if I hooked up 2 new DC27 with 3 older DP27 batteries in parallel on my Fifth Wheel camper?

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

    Reply  •  July 15, 2014 at 8:00 pm
  • Michael
    I have 6 12v 100amp batteries wired in series powering a 72 volt motor. I want to charge them all with 500 watts of solar via 12 volt charge controller while leaving them wired in series. My question is how can I safely do this if possible without having to untie the series connections and then rewire the bank in parallel to attach to the controller every time I want to recharge the 6 batteries. Can I theoretically wire a positive/negative connection from the 12 volt charge controller to each battery individually basically charging them up as an isolated 12 volt battery (without having to disconnect the series connection.. and obviously the motor is not running and I have no 72 volt load while this is happening).. or better yet I pull a positive and negative wire from each battery to a separate bus bar that will now be 12 volt and connect the controller to that bus bar to charge all the batteries at the same time even though they are all still connected in 72 volt series as well that is not pulling any loads?


    Due to the fact that we don’t have all the information for your system we would need you to contact us at so that we can ask the appropriate questions, to get you the answer that you may need.

    Reply  •  July 9, 2014 at 4:58 pm
  • Shannon
    I have two 24V lights and a 24V winch I would like to put on my pickup. If I take two 12V batteries hook them in series to power the 24V accessories. Can I charge each battery with my 12V alternator if I wire them on there own circuit without doing any damage to my truck? Thanks

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

    Reply  •  Rated article 5  •  July 9, 2014 at 5:51 am
  • Jonathon
    I have an RV with 6-6 volt batteries connected in series. The top of the battery says 232AH. I am wanting to install a refrigerator that uses 445 kWh/yr. How long will my batteries support this until they die?

    Thank you!


    Due to the fact that we don’t have all the information for your system we would need you to contact us at so that we can ask the appropriate questions, to get you the answer that you may need.

    Reply  •  Rated article 5  •  July 6, 2014 at 4:53 pm
  • Dragan
    Hello! I need help. I have a 700VA UPS with AVR that I use on a daily basis. Can I plug it into a 12V solar charger to charge it? Battery inside UPS are 12V 10Ah. I plan to drill the chassis of the UPS and connect solar controller and solar panel 12v directly to the battery, not moving the existing wires. Is it safe to do something like that?

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

    Reply  •  Rated article 5  •  July 2, 2014 at 6:21 am
  • Kory
    I have an RV with 2 identical Interstate Batteries 12V wired in Parallel. Last weekend we were plugged in, so there shouldn’t have been a draw on the batteries. The one that was added in aftermarket really got hot, smelled of sulfur and the other one was fine. Do I have one bad battery or do I have an electrical problem? Both batteries are approx. 2 years old.  

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

    Reply  •  June 30, 2014 at 5:54 pm
  • Rizqi
    I have 3 battery with 12V 75Ah and 1 battery with 12V 80Ah. is it possible if I install those 4 ea (all) battery with serial connection ? is it safe ? or it will make damage the battery.

    Thank you.

    Reply  •  Rated article 5  •  June 23, 2014 at 10:00 am
    • BatteryStuff Tech
      While it is commonplace, it is not recommended to do so. You will shorten the life of some or all of the batteries by doing so. We only recommend tying like size, type, and age batteries together in a system. Thanks

      Reply  •  June 25, 2014 at 9:10 am
  • John
    I have a battery pack with 2 aaa’s connected in series to make 2.4 volts 800mah. Is it okay to connect 2 of these in parallel to increase the current? I see that you can do the exact opposite…Parallel/Series. I need to know if Series/Parallel is okay, too.

    Reply  •  June 7, 2014 at 4:43 pm
    • BatteryStuff Tech
      Yes that is fine.

      Reply  •  June 16, 2014 at 10:53 am
  • Ted
    I have bought a used 2004 48 Volt Club Car Golf Cart, It currently has 8, Six Volt Batteries! I want to change to 4 12 volt Batteries? Is this possible and what are the down falls of doing so?

    Reply  •  Rated article 5  •  June 4, 2014 at 8:03 am
    • BatteryStuff Tech
      Ted, yes it is possible, but typically would not be recommended. 6 volt golf cart batteries are made with very thick plates, which lends them to long life and durability. If you are able to find 12 volt batteries to replace yours that are rated at a higher AH rating that then 6 volts, then it may make sense, but typically it does not.

      Reply  •  June 16, 2014 at 10:53 am
  • Rakesh
    I have two x 12volt battries connected in series by 24volt solar charge controller, I requir 12 Volt DC for inverters and UPS separatly. Will it sufice to connect both the UPS and inverter separately to both the battries besides being in series.

    Reply  •  June 2, 2014 at 7:16 am
    • BatteryStuff Tech
      It is not recommended to do so. I would recommend using a step down converter to ensure that the batteries are drawn down evenly.

      Reply  •  June 2, 2014 at 8:54 am
  • Snazzy
    Help me here. I have 16 6v batteries connected in series & parallel to give me 2 banks & 48 volts. My outback system seems to be working fine but one bank of the batteries is always a lower sg so I assumed not as charged. Any suggestions

    Reply  •  Rated article 4  •  May 23, 2014 at 10:21 pm
    • Admin
      Please email your question, along with the complete specs of your system to

      Reply  •  May 27, 2014 at 9:42 am
  • BatteryStuff Tech
    As long as your system is sized appropriately. That would still be 12 volts.

    Reply  •  May 23, 2014 at 2:14 pm
  • John
    Hi there!
    Can I connect 8 ×12volts deep cell Marines batteries in Parallelle to a 12 volts inverter?I have 4 ×160 watts 12volts pv



    Reply  •  May 23, 2014 at 1:12 am
  • David
    Hellow ok, i have two diffrent brand batteries, now is it ok to use 1 brand for just volts/series, and the other brand parallel?

    Reply  •  May 17, 2014 at 10:25 am
    • BatteryStuff Tech
      David, so are there 4 batteries then?

      Reply  •  May 21, 2014 at 12:30 pm
  • Richard
    OK another parallel battery question. I have an external 12V 55Ah battery connected in parallel to boost the life of an internal 12V 16Ah battery in a piece of equipment that draws about 12V 8W 24/7. This all works fine. However if I remove the external battery and recharge the internal 12V 16Ah battery it now does not retain its charge. All batteries are lead acid, the internal batteries are deep cycle and the external batteries are ‘car’ type batteries.

    Reply  •  May 12, 2014 at 11:34 am
    • BatteryStuff Tech
      Richard, connecting a 55AH battery to a 16Ah battery is asking for trouble. Most likely the 16AH battery has had it’s guts cooked out, and the system is only working off of the 55Ah battery. Which would explain why removing the 55AH bat causes the system to stop working. We always recommend same type, size, age when using batteries in series or parallel. For more specifics in regards to your application, please email us directly at Thanks

      Reply  •  May 12, 2014 at 12:19 pm
  • Steve B
    I just replaced the two ancient, weak Interstate flooded batteries with a pair of Lifeline AGMs. They’re house batteries in my RV and they’re wired in parallel.

    I checked the voltage of each battery before installing them (12.82v).

    I’m wondering if there’s a way to test the batteries now that they’re wired in parallel. (I got a reading of 14.35v by connecting the multimeter to the RV’s Progressive Dynamics converter, but the number doesn’t make much sense to me.)

    Reply  •  May 2, 2014 at 5:42 pm
    • Admin
      Steve, please email your question directly to There are several different ways to test batteries, and they should be able to answer your question. Thanks

      Reply  •  May 12, 2014 at 12:16 pm
  • Charles
    First time at this site and have it book marked.

    I’m working on an ebike build.

    The drive system will be brushless hub motor at 250 watts 36 volt for the rear axle.

    The recommended power power from the battery or batteries is 44V/5Ah at 220 watt hours.

    I new to this, but I like to build things. My mountain bike does not have much room for the rather large bulky batteries because it has front and rear suspension.

    I’d like to use a bank of smaller batteries instead and arrange them around the frame or in a saddle bag. Some ebikers are using recovered laptop batteries. I like use try the Lipo packs used in remote controlled planes. The batteries come in many different shapes and sizes. How can put together a group to drive the motor at the recommended voltages and to get the best range? Oh, and I almost forgot. I’ll need a good charger. So what would the charge specs be also.

    With all of our battery powered needs from cars to phones, DIY is liberating and fun.

    Thank you. Charles

    Reply  •  April 26, 2014 at 11:26 pm
    • Admin
      span class="caps">DIY is fun! :) For technical advice, please email the question to and a tech will respond with their recommendations. Thanks

      Reply  •  May 12, 2014 at 12:15 pm
  • Andy
    Thanks chaps, this is a very interesting site.
    I found it trying to get some idea of how to prolong the use of sets of used ,half dead golf cart batteries on a stand alone 24 V solar system.This is only a non essential system I play around with having nothing better to do but it still runs my fridge as a bonus!
    Currently I have 3 strings @ 24 V connected in parallel.Current draw is 12 Amps max about 18 hours every 24 hours.Some cells discharge more than others (on days with no sun),it automatically disconnects when the Voltage gets to 23.0 Volts.
    Now the question I wish answered:where in the string setup should the worst of the cells be and what is the benefit or disadvantage of adding more semi faulty batteries to the system.
    Kind regards

    Reply  •  April 17, 2014 at 9:56 pm
  • Shashank Sharma
    i have one circuit for mobile charger and one dynamo circuit both of them having different jumper wires can i connect them two the same battery of 12v and 7ah using their jumper cables

    Reply  •  April 17, 2014 at 6:17 am
  • Maurice
    if I have 24 2 volt 540 amp hour batteries in a series does that mean I would get 26 kw of power for my home per hour 48 volts x 540 amps = 25920 watts is that correct

    Reply  •  April 12, 2014 at 8:25 pm
  • Jules
    Hi, i have four 6v 225ah batteries I’m installing in my boat, the usual setup seems to be first to series two 6v batteries to achieve 12v then parallel the two series together however your diagram shows paralleling two batteries first then series to achieve 12v, What are the advantages/disadvantages of doing it the way you show?, I’m very keen to set my setup like your diagram given my battery locations – thanks

    Reply  •  Rated article 5  •  April 6, 2014 at 5:31 pm
  • Jules
    Hi, i have four 6v 225ah batteries I’m installing in my boat, the usual setup seems to be first to series two 6v batteries to achieve 12v then parallel the two series together however your diagram shows paralleling two batteries first then series to achieve 12v, What are the advantages/disadvantages of doing it the way you show?, I’m very keen to set my setup like your diagram given my battery locations – thanks

    Reply  •  Rated article 5  •  April 6, 2014 at 5:29 pm
  • Sunil Vijaya
    i wonder whether you can help me a solar power set up. i have a hybrid home with 6 panels each 80w 18v 4.45amp. i have 4 agm batteries 2 – 90ah and 2 – 70ah. i need to power my air con which is 930w 9000 btu. what is the battery bank i need? can i increase the solar panels output and keep the same battery bank?

    Reply  •  Rated article 5  •  April 6, 2014 at 2:43 am
  • Helen
    We have 24 batteries 2 volt each just wondering I what sort of charger we would need to charge

    Reply  •  April 4, 2014 at 12:49 am
  • Stacy Kermode
    I bought a Travel Trailer in February they stored it for me until April 01/14, when i got it home i noticed the batteries wont power anything on trailer.(Two 12volt deep cycle batteries wired in parallel)its now sping but still cold. Are my Batteries now crap or can they still be charged and if so do they need to be charged separately or can they be charged together and how? do they need to be removed from trailer or can i charge them on trailer? do they have to be warmed up first and how long? SORRY for so many questions but im worried about them. Any help would be greatly appreciated! THANKS!!!!!

    Reply  •  April 2, 2014 at 4:26 pm
  • Mike Cooper
    Hi, Found this site/thread researching charging rate/outputs for a leisure battery. What a good site.!!You solved my problems. A BIG THUMBS UP.!!

    Reply  •  March 27, 2014 at 4:29 am
  • Ryan
    I have a NOCO Genesis (1bank) battery maintainer/charger. However, I have two batteries wired in series with a blue seas system switch. My question is, can I wire this charger to maintain both batteries or only one? Also, how should I wire it with the switch to get both if possible?


    Reply  •  March 20, 2014 at 8:55 am
  • Francie
    if my total battery capacity is 2000Ah, but my specs states that the battery bank is 2 × 50% does this mean i will be using only 1000Ah? thanks for the response.

    Reply  •  March 17, 2014 at 6:42 pm
  • Kaye
    So if I need to charge my discharged battery, what would be the ideal way to connect them? In series or parallel?

    Reply  •  March 16, 2014 at 1:16 pm
  • John Prowse
    I have a mobility scooter with 3 × 12v batteries wired in series to give 36v. I want to go lithium, but have been told that the battery management system won’t allow a 36v charger to charge a bank in series, and that I would have to charge each battery independently with a 12v charger. Does that sound right to you? Thanks for all the info in this article, by the way. Very useful indeed.

    Reply  •  Rated article 5  •  March 11, 2014 at 7:32 pm
  • Danny M
    Im trying to get my son’s 91 Club Car to go a little faster. We recently purchased/installed 6 new Trojan 6v batts. Found the cart very slow up hills, decent on flat surface and very fast downhill. I have several questions, please: Someone told us we could replace 2 of the 6v batts with 2 8v batts. I did this, but accidentally crossed up the cables when putting in the new 8v batts (i.e., I hooked up the NEG from batt #3 to the NEG of batt #4, etc.) Then I ran the charger overnight. Did I hose the batts in any way by connecting improperly? I tested the cart the next morn and it was terribly slow, so I checked the cables and found my error. So, I reconnected properly (each NEG to the next POS in a series, etc.) and charged the cart again until the charger shut off. Again, we have nothing – slower than slow on flat surface, wont climb hills at all and wont move in Reverse. Now they are saying it must have been a charging problem (with mixed batt voltages)and say we should replace all of the 6 6v batts with 5 8v batts and still use our 36v charger. They said that by having 1 less batt and 4 more volts it would help the cart go faster up hills… Will this work? Is this worth the change? What Im most worried about is: Will the 36v charger fully charge the 5 8v batts? Should we just stay with our 6 6v batts and be slow up the hills? Thanks much! Im novice at this golf cart maintenance thing and want to help my son. DM

    Reply  •  March 9, 2014 at 7:00 am
  • Trapper
    i have 4 3.7v li-ion batterys if i putt them in para/ser would that run a 5v bluetooth chip two low volt amp chips and about 30 leds andd maybe a circut or twwo more or do i need to do one or the other

    Reply  •  March 7, 2014 at 11:41 pm
  • Gordon
    Thank you very much for being available to help those of us who are weekend techs with our toys. After reading your article and responses, I hope that I was correct in setting up my 2 dual purpose marine batteries (EverStart Maxx Group 24 (Model MAXX-24DC))in parallel. My purpose for parallel was to provide powerful cold cranking and marine cranking amps while having plenty of amp hours for my tilt/jack plate/GPS/gauges. My biggest question refers to trickle charging this set up. Since these are marine dual purpose batteries joined in parallel, I was wondering which Tender Junior charger I should use to keep them charged? Thank you in advance for your expert advice, Gordon

    Reply  •  February 23, 2014 at 10:23 am
  • Kenny Schwartz
    Ignore second comment. Just realized that’s not possible with only 2 batteries and am again lost.

    Reply  •  January 18, 2014 at 3:16 pm
  • Kenny Schwartz
    I sent a question comment to you a couple minutes ago and believe I figured it out on my own just now. For the car stereo issue I would do a single battery series parallel setup running the back battery on it’s own seperate parallel circuit then linking it to the front one with a single wire between the two positive posts. That would essentially give me double the capacity without multiplying the voltage or amperage output from creating a bank while keeping them on the same charging system.

    Reply  •  Rated article 5  •  January 18, 2014 at 2:53 pm
  • Kenny Schwartz
    I have a 1000W 2 channel amp powering 2 pioneer 1300W Subs in my car. I’d like to put a dry cell battery in my trunk so I can play my music at car shows without having to start the car or worry about it being dead when I go to leave. Assuming they’re both equal voltage and CCA ratings would I want to wire them in series or parallel and could this cause any issues with say blowing light bulbs or starting fires etc… with the factory wired components or would I have to put a resistor before the fuse box in order to correct the issue and would that negate the benefit of having 2 batteries? Obviously i’d be using somewhere around a zero guage wire for the job.

    Reply  •  January 18, 2014 at 1:55 pm
  • Kirk
    Thanks for the great info, Tech!

    The situation:
    Say I’m setting up a 12V house bank for my boat, something like 800 amp-hour of capacity, probably 4 200 amp-hour 12V batteries in parallel. I’ll have an inverter that recommends a 400 amp fuse at the battery. The system will also have a 150 amp alternator for charging from the engine, and a DC distribution panel whose main breaker is 150 amps.

    The question:
    How do I pick the right size cables for the “bridges” within the battery bank? Does it matter which battery serves as the “top”, where the main feeder is connected?

    Thanks for a great resource!


    Reply  •  Rated article 5  •  December 9, 2013 at 12:13 pm
  • Gerard
    I have a 48v golf cart, consisting of (4) 12v batteries. I would like to hook up 12v accessories to it. Is there any problem with hooking the 12v accessories directly to (1) of the (4) batteries? Is a voltage reducer necessary?

    Reply  •  December 1, 2013 at 8:40 pm
  • Dwight
    Question, I have a bank of 420 ah,48v (12v 105ah AGM-identical batteries)why is it that I find that over a 3 day period one of the 4 batteries in series have less charge. i.e. 3 has 12.7 and 1 has 11.7v; to prevent me from losing the battery, I have to charge that battery independently, then put it back in series……… work for another 3 days then all over again, any suggestion Tech?

    Reply  •  May 29, 2013 at 9:57 pm
    • Jeremy Fear
      If one battery is draining faster than the others, when they are all in a series, then I woudl surmise that it is either older than the others, or it may have a cell that is not functioning correctly. We always recommend using the same type, size, and age batteries when you ar tying them together in a system. (That goes for both parallel and series connections.)

      Reply  •  May 30, 2013 at 8:13 am
  • Jonathan
    I am working on a backhoe with two 12volt batteries hooked in series to make 24volts. With engine idling one battery is charging at over 14.5volts while the other battery is just under 13volts. What would cause this? The battery that is charging at under 13volts is only 12.88volts with engine off and 12.99volts with engine running.

    Reply  •  Rated article 5  •  May 20, 2013 at 2:56 pm
    • Jeremy Fear
      It could be a variety of things, however, it sounds like either the batteries are mismatched, or one is failing and is pulling the other one down.

      Reply  •  May 21, 2013 at 11:28 am
  • Shujaat
    I have a solar panel with 60V and 10A with power = 600W. I have a stock of 12V and 125A batteries. So Which configuration(series and parallel) and effective voltage of batteries i need to properly charge batteries.

    Reply  •  May 20, 2013 at 2:13 am
    • Jeremy Fear
      Series would be the correct configuration for the batteries, however without a controller it still will not work for you. The controller keeps the solar panel from inputting too high of a voltage directly into the batteries, which would hurt them. I would not use these panels on those batteries without a controller. The unfortunate part is that we do not have a controller that will operate on 60 V.

      Reply  •  May 20, 2013 at 2:03 pm
  • Jose
    I have two separate 120Ah gel batteries in a boat. One is for supporting the single engine on-board, and the second one for all the other on-board services.
    There is a switch on the positive (+) that allows both batteries to run in parallel if needed.

    The installation comprises a single negative cable (large cross section: 95 mm2) that connects the engine and the engine negative battery pole (Cable NEG A)

    A similar AWG cable (Cable NEG B) interconnects the negative poles of the two batteries. The battery charger outputs 12.5A on each of two individual cables connected to the positive poles of each battery. A negative lead is connected to the large negative cross section cable.

    My question is the following:
    Can I replace the “Cable NEG B” with a cable of smaller cross section (50 mm2) with only a length of 40 cm and use a negative bus bar for connecting the services individual wires?

    Basically I can reformulate the question in the following manner: there is any requirement for the negative return between both batteries when they are in parallel to have the same cross section of the positive leads? If so would a minor distance (40 cm) be a big deal considering that a cross section of 50 mm2 can cope with more than 250A of current at 12V?

    Your comments would be greatly appreciated and congratulations for a great blog. Thanks

    Reply  •  Rated article 5  •  May 16, 2013 at 4:31 am
    • Jeremy Fear
      Yes, it is always a good idea to have the negative and possive wires the same guage. While it may work out just fine, we always recommend using the same size and type.

      Reply  •  May 20, 2013 at 1:48 pm
  • Diane
    Thank you for this great blog. We currently have a 48v wind/solar system with 8- 6V 230AH deep cycle batteries in a series. We just purchased 4 more to add to them, exactly the same batteries. The originals are almost new, too (just spreading out paychecks!). Question is, how do we wire them in to add more amps but not add voltage?

    Reply  •  Rated article 5  •  April 26, 2013 at 6:07 pm
    • Jeremy Fear
      You would have to have the same amount of batteries to add to the system (in this case 8) and then you would wire them in series to each other, and then the entire bank in parallel with the other bank.

      Reply  •  April 29, 2013 at 9:30 am
  • Mark
    I have 6 12 volt batteries wired in parallel, trying to create a jump cart for diesel rigs like Peterbilts. It will not jump start the trucks any ideas why and what I could do differently. The trucks are 12 volt systems

    Reply  •  April 18, 2013 at 4:13 pm
    • Jeremy Fear
      I would first check to see if those trucks are 24 volt. A lot of the larger Diesels are 24 volt. Thanks

      Reply  •  April 24, 2013 at 9:24 am
  • Wilson
    Hi, I am currently running two 12V 40 Ah Exide Solar Tubular batteries in 24V solar power system.
    I am planning to enhance the battery capacity.
    Simple way is to buy two more 12 40AH batteries.

    But is it good to build a battery bank like this:

    two 12v 40 AH in parallel bank and one 12v 75AH battery in series with it.

    I would like to know whether it would create any charging or capacity issues?
    I have a 12V 500W panel array.

    Reply  •  Rated article 5  •  April 10, 2013 at 11:05 pm
    • Jeremy Fear
      Yes, there could be charging issues with that setup. The best way to do this would be to not have a single 12 volt 75 amp battery, but instead to have four 40amp, 12v batteries in a series parallel configuration.

      Reply  •  April 15, 2013 at 8:06 am
  • Kev
    Hi, what happens to the Rated Discharge Current and Max Continuous Current when cells are conected in Parallel? Will this increase in the way the Ah capacity will?

    Reply  •  Rated article 3  •  April 10, 2013 at 1:12 am
    • Jeremy Fear
      In a parallel circuit amperage is increased while voltage stays the same, so yes, amperage (current) will increase in parallel.

      Reply  •  April 10, 2013 at 9:26 am
  • Denny
    Wondering about how much voltage/amperage I can put into the batteries. I have 6 × 12v deep cycle batteries in parallel and I know I can charge them all with my 2amp and 12 amp chargers, but could I also charge them with something of higher wattage or voltage. (I have a 190W solar panel that is 36v and it outputs about 6amp.), Can I put 5 of those panels together to get 30amp out of them and still charge the batteries. I could definitely use the energy so the batteries would never over charge. Any pointers would be appreciated.

    Reply  •  March 26, 2013 at 1:20 pm
  • Paul

    Reply  •  Rated article 5  •  March 14, 2013 at 11:11 pm
  • Paul
    I am replacing battery packs in an emergency lighting unit. 4 6v 7.2ah batteries are needed. the wiring has been removed and I will be rewiring it. the packs drive 4 sets of lights through out my business. I am not sure if I should wire them in series, parallel or combination. the side of the light unit has been marked 12v 200watt by the previous owner. the unit is wired to the building correctly, I just need help on the battery pack wiring. any help would greatly appreciated!

    Reply  •  Rated article 5  •  March 14, 2013 at 6:28 pm
    • Jeremy Fear
      We recommend having a liscenced electrician instal the batteries. From the looks of it, you will need a parrellel/series combination, however I am unable to verify that for sure. Thanks

      Reply  •  March 18, 2013 at 9:03 am
  • Eme
    Im working on an experiment for an art exhibition. Where i need to power a small 1.5-3volts 0.2amp engine with lemons. Each lemon provides around 1volt and 0.001amp. To lower the amount of lemons that i would need to power the engine is there something to increase the amperage, a capacitor perhaps? thanks!!

    Reply  •  March 5, 2013 at 1:33 pm
    • BatteryStuff Tech
      As amperage increases, the natural result will be a decline in voltage.

      Reply  •  March 5, 2013 at 2:28 pm
  • Fred
    I have a off grid system and have acquired a second battery, First one is a 280AH AGM battery and second one is a 230 AH AGM Battery, Is this going to be an issue to connect the second battery in series to the First, Will it cause any problems, Is there a safe way to connect it if not, Cheers In Advance

    Reply  •  March 5, 2013 at 10:03 am
    • BatteryStuff Tech
      The larger capacity battery will feed into the smaller capacity battery in an attempt to bring it up and equalize capacity. Because it is impossible for the smaller battery to increase in capacity, you will see early failure on both batteries as one will be constantly draining and the other will be overcharged. This happens automatically by simply connecting the batteries together. This unbalance can also happen when charging them together.

      Reply  •  March 5, 2013 at 10:37 am
  • David McNamara
    I have six deep cycle batteries, a 3,000 watt inverter in my horse trailer. I have a 250 watt refrigerator and 2 12 volt fans. How do I connect batteries to get the longest time out of them. I have two 15 watt solar panels.

    Reply  •  February 25, 2013 at 7:18 am
    • BatteryStuff Tech
      What are the voltage of the batteries? And what is the input voltage rating on the inverter?

      Reply  •  February 25, 2013 at 9:07 am
  • Emerson
    Is this ok? 7.2v 6batery AA 500mah cmbine with 8.4v 7 biger than AA1500mah? Plz get bck to me asap b4 itry tnx

    Reply  •  February 22, 2013 at 6:08 pm
    • BatteryStuff Tech
      I don‘t recommend it.

      Reply  •  February 25, 2013 at 8:53 am
  • Andrew
    I have 11 × 15Ah (12V) batteries and i‘m looking at hooking them up into a 24V configuration. I was planning on having 2 × 12V banks (one with 5 batteries and one with 6 batteries). Is this wise or would i get a better result just have each 12V bank with 5 batteries?

    Reply  •  February 17, 2013 at 9:58 pm
    • BatteryStuff Tech
      It‘s better to keep the banks even, so it looks like you should use 10 batteries.

      Reply  •  February 18, 2013 at 9:22 am
  • Shoumya
    Is there any way so that we can switch from one connection type to the other??

    Like I will be connecting two 12V,6A batteries in parallel as power source for my robot..this will give a 12V,12A output.ryt?? Now if i want want to give a temporary boost..i can connect the batteries in series which will give 24V,6A.

    Reply  •  Rated article 4  •  February 12, 2013 at 11:52 pm
    • BatteryStuff Tech
      If you have both a series connection and parallel at the same time, you will cause a short to occur. You will need some pretty fancy wiring and switches to prevent both configurations from ever occurring simultaneously. Good luck with that.

      Reply  •  February 13, 2013 at 8:56 am
  • Jeswills
    I have 800VA inverter with 12v and 1 200amp then 2 100amp deep circle batteries connected parallel. One is that the batteries were bit by the rain after i moved from my former apartment where a professional connected it for me. Now i just want to connect it to my 12amp room socket, still parallel but i earlier put d charger clamp positive onto another battery and negative to another and it showed low battery at once after charging it for hours. So now i put d clamp positive and negative to one battery in d bank. Do u think i might have done something wrong?

    Reply  •  February 12, 2013 at 6:38 pm
    • BatteryStuff Tech
      Am I correct to assume you have three batteries connected in parallel? One with 200 AH, and two with 100 AH each?

      Are these wet batteries, or sealed batteries?

      Reply  •  February 13, 2013 at 8:46 am
  • Jordan
    Hey mate we are buying a bus and doing it up. Franky all this battery mumbo jumbo makes me want to go back to school. We were thinking about having 6 deep cycle 12v batteries in the back of the bus to power a heap of equipment. I was wondering how we would go about bringing that to 240v and how would we charge all those batteries. We thought that we might have something set up from the alternator but that many batteries to charge would take way too long. This plan will be happening towards the end of the year but we are just trying to figure out what we need and dont want to be screwed over by anyone.

    Reply  •  February 9, 2013 at 11:47 pm
    • BatteryStuff Tech
      If you need 240 VAC, then I recommend using an inverter to transform the 12 VDC to 240 VAC. The batteries can either be charged by 12 volt solar panels or an AC powered battery charger when the bus is parked.

      Reply  •  February 11, 2013 at 11:00 am
  • Gil Bishop
    Hi, I have an RV with 4-6V/200AH AGM batteries in series/parallel used with a 2800W inverter-charger. I want to add more capacity, but I know I can‘t mix old and new batteries in the same bank. So if I add a separate second bank (with the same configuration), is there a way to have the inverter-charger service both banks, using a manual switch or preferably some kind of automatic load-balancer? Any suggestions or “gotchas” are appreciated! Trying to avoid replacing the large and not-too-old investment in the existing batteries if at all possible.

    Reply  •  Rated article 5  •  February 6, 2013 at 10:02 am
    • BatteryStuff Tech
      Inverters are designed to pull from a single source. If you do put a switch, it will have to be one bank or the other. The moment you switch to ‘both’ you suddenly have connected both banks (old and new) to each other.

      Reply  •  February 6, 2013 at 10:36 am
  • Wasim Sohail
    I have load of 500 Watts for 8 Hours. What capacity batteries required for longest life, and how should I arrange them.

    Reply  •  Rated article 5  •  February 6, 2013 at 9:33 am
    • BatteryStuff Tech
      Please use our load/battery capacity calculator in the tools section of our Knowledge Base to find the answer you are looking for.

      Reply  •  February 6, 2013 at 10:25 am
  • Ivan
    Hi, i have my RC Helicopter, but it‘s so hard to buy replacement battery with specs 7.4V 180mAh, now i do have 6-AA 1.2V 2000mAh, if i connect them in series i will have an output of 7.2V 2000mAh, will it burn my RC‘s PCB board(power board), if i increased the mAh? or it will be okay?

    Reply  •  Rated article 5  •  February 4, 2013 at 11:50 pm
    • BatteryStuff Tech
      Increased capacity will only give you longer runtime. As long as the voltage (the pressure) is within safe range, then I see no danger in your proposed setup.

      Reply  •  February 5, 2013 at 12:39 pm
  • Paul Z
    Happy Ground Hog day! I live off the grid and have a 48V system consisting of 8 L16 380AH batteries strung in series. One of the batteries died the other day. As with others above, I hate to spend $3,000 on new batteries because one has died. Can I replace the one L16 with 2 cheapo 6V 225AH batteries in parallel, then connect them in series with the remaining 7? If I understand correctly, the 2 cheapo‘s will never fully charge and will be stressed more than the other batteries. But if they extend the life of the remaining 7, by a year or more, it will be well worth it.

    I was able to adjust my outback solar controller and inverter to handle the 42V system I‘m running with 7 batteries, but I‘m not sure if this is putting any stress on those components.

    Reply  •  Rated article 4  •  February 2, 2013 at 2:39 pm
    • BatteryStuff Tech
      Replacing one battery will technically work, but like you said it will cause the rest of the batteries to forsake whatever natural lifespan they would have had. All you are doing it postponing the inevitable. Someday you should replace all the batteries at the same time.

      Reply  •  February 4, 2013 at 12:25 pm
  • Sajib
    As in text book we can see two DC batteries/Sources are connected in series,while the one is of reverse polarity of the another ( that cause to establish two currents with opposite direction of each other). Under such a series connection, the resultant voltage is measured by subtracting the lower voltage from the higher one. And finally direction of current can be determined after we calculate the resulting voltage.
    Now, I wonder whether such a series connection is experienced in our real life, or such a series connection of sources can damage the device (I mean negative terminal of one Battery is connected to negative of another battery OR the vice versa )?

    I would appreciate your time answering me.


    Reply  •  February 2, 2013 at 1:29 pm
    • BatteryStuff Tech
      Series is a positive terminal connected to a negative terminal from another battery. But if the polarity is reversed on the second battery, therefore it would be the equivalent of connecting two positive terminals to each other. Because it would be an incomplete battery bank, a system using batteries like this will experience problems.

      Reply  •  February 4, 2013 at 12:22 pm
  • Tom C
    I have two 12 V batteries in my boat with a shorepower charger. Recently both batteries were completely dead. I check shroepower and had 120V to the charger. Charger output was 6 V rather than 12 V. Could this actually drain my 12 V batteries?

    Reply  •  February 2, 2013 at 7:00 am
    • BatteryStuff Tech
      Is the charger a 12 and 6 volt charger selectable with a switch?

      Reply  •  February 4, 2013 at 12:13 pm
  • Bob
    I would like to know what it would take to run an average house in deep cycle batteries,inverter,and charging source.say 180 amp service.

    Reply  •  January 30, 2013 at 11:47 pm
    • BatteryStuff Tech
      Is 180 amps the average draw about? Is this hourly? For how long do you plan to run the house on batteries before needing to recharge them? Is the 180 amps taken from 12 volts DC? Or 120 volts AC?

      Reply  •  January 31, 2013 at 9:44 am
  • Mick
    Very good info and great answers

    Reply  •  Rated article 4  •  January 29, 2013 at 10:21 am
    • BatteryStuff Tech
      I‘m glad you find our information helpful.

      Reply  •  January 29, 2013 at 10:25 am
  • Mick
    Very useful information. I have a question.
    When you have 10 6 volt 220a/hr batteries and you want to to have a 12 volt bank which is a better way to connect them, in series banks of 2 batteries each then connecting them in 5 parallel banks or making 2 parallel banks of 5 batteries each and putting those 2 banks in series? Both ways give you them same A/hr output and 12 volts.

    Reply  •  January 29, 2013 at 10:20 am
    • BatteryStuff Tech
      It makes no difference.

      Reply  •  January 29, 2013 at 12:18 pm
  • Kelly
    how many car batteries do i need to run a house using 2000 KwH and what size of an invertor do i need?

    Reply  •  January 28, 2013 at 4:50 am
    • BatteryStuff Tech
      Please do not use car batteries for a deep cycle application. KwH is a measure of energy, not power, so I need to know the time period associated with your number.

      Reply  •  January 28, 2013 at 9:47 am
  • Paul
    Hi is it possible to have 12 volts battery‘s configured as 24 volts but still charge them with 12 volt solar panels ?

    Reply  •  Rated article 5  •  January 27, 2013 at 5:33 am
    • BatteryStuff Tech
      No. Either disconnect the batteries for charging, or buy another solar panel and wire it in series to create a 24 volt solar system.

      Reply  •  January 28, 2013 at 9:28 am
  • Kev Wren
    hi, I intend to bank two batteries in my rv in parrelel to increase stored ampage.. i have a 110 ah deep cycle and a 80 ah normal cycle , can these be banked together? thank you

    Reply  •  Rated article 1  •  January 27, 2013 at 3:31 am
    • BatteryStuff Tech
      I don‘t recommend it.

      Reply  •  January 28, 2013 at 9:27 am
  • Brian
    Could the overheating battery on the new Boeing 787 Dreamliner be a simple case of incorrect wiring configuration. I know it might seem so simple it‘s stupid. But I cant help but feel it could be over looked. Just my 2 cents.

    Reply  •  Rated article 5  •  January 24, 2013 at 6:56 pm
    • BatteryStuff Tech
      Incorrect or inadequate wiring and connections can result in overheating and in some cases, melting of adapters and terminals. It may sound simple, but it‘s not a silly suggestion.

      Reply  •  January 25, 2013 at 12:05 pm
  • Gpeg
    Hi again, I see from the series/parallel diagram that you show connecting batteries that are in parallel with each other, to another pair of batteries (in parallel as well) using a series connection. Is it possible to take two banks that are connected in series, and connect them to each other in parallel? Where would you connect the leads in that case? thanks again for your help

    Reply  •  January 24, 2013 at 6:19 pm
    • BatteryStuff Tech
      Yes, what you suggested can also work to accomplish the same output. If you have two batteries in series, then technically there is only one ‘open’ positive and negative post in each bank. These are the posts that you should connect in parallel.

      Reply  •  January 25, 2013 at 11:47 am
      • Gpeg
        Thanks for the help. Once the series/parallel connections are complete, where is the most optimal place to connect the leads that bring power out of the pack(s) It appears all the open terminals would be taken iwth this arrangement.

        Reply  •  January 26, 2013 at 5:56 am
        • BatteryStuff Tech
          Every post that is used in a parallel connection (for example all of the positives connected to each other) will all act as a single positive terminal. Therefore, you can technically use any one of them as the entry point. The same can be done for the negative side. It‘s your choice.

          Reply  •  January 28, 2013 at 9:14 am
          • Gpeg
            Great, that makes it easier. What about charging? Can I hook the charger leads in the same way?

            Reply  •  January 30, 2013 at 8:02 pm
            • BatteryStuff Tech

              Reply  •  January 31, 2013 at 9:42 am
              • Gpeg
                Hi, thanks again for all of your information. Since my last question I‘ve upgraded the battery pack in my EV to 120 volts @100 AH. Given that the motor will also run if I make my battery pack into two 60 volt, 200 AH packs in parallel, do you think there‘d be any advantage in range? Obviously performance would suffer, but would range be increased? Your thoughts would be very helpful. Thanks,

                Reply  •  March 7, 2013 at 8:08 pm
                • BatteryStuff Tech
                  120 v x 100 AH = 12000 Watts. 60 v x 200 AH = 12000 Watts. The total amount of potential power is the same. The motor will run slower at 60 volts. If the demand on the motor is constant, the lower available voltage will cause the motor to pull more amps in order to run properly. Therefore, having more amp hours may not give you the impression of longer runtime if your pulling more amps at a time.

                  Reply  •  March 8, 2013 at 8:50 am
                  • Gpeg
                    Hi, thank you again for all of your helpful information. I‘ve begun testing my 120 volt EV conversion and it runs very nicely. I‘m trying to determine how deeply I‘m draining my pack on recent trips. For instance, after my last run the battery pack tested at 124 volts after sitting two hours. According to the charts I‘ve seen, that means the pack is at 75-80% capacity at this level. All the sites I‘ve seen recommend letting the batteries sit for 6 hours before testing. What inaccuracies will I get with the two hour test? Is it going to be a false high, or a false low reading? Thanks again

                    Reply  •  March 31, 2013 at 6:06 pm
                    • Jeremy Fear
                      I would be a false low, though 2 hours would be long enough to be accurate within half a volt.

                      Reply  •  April 1, 2013 at 8:17 am
  • Mark
    I have a light that runs off of a 12v car battery and draws 1 amp that I use for fishing. However, carrying a 12v car battery around isn‘t the most convenient. Could I hook two 6v lantern batteries in series to make a 12v system that would run the light? And if so, any idea approximately how long I could run the light for?

    Reply  •  Rated article 5  •  January 23, 2013 at 1:23 pm
    • BatteryStuff Tech
      Two 6 volt batteries in series will work to power the light. The length of time you can run the light depends entirely on the capacity (amps) rating of the 6v batteries.

      Reply  •  January 23, 2013 at 3:53 pm
  • Sandy
    My wife and I are looking at building an off-grid house in the mountains (solar, wind, and generator). We were discussing our battery bank options with a friend, who recommended 24 2V batteries. Another friend recommended two banks of 8 6V batteries. Which one sounds better?

    Reply  •  January 21, 2013 at 7:06 pm
    • BatteryStuff Tech
      If you can, choose the 2 volt option.

      Reply  •  January 22, 2013 at 9:04 am
  • Kenny
    I am trying to figure out which was is better for running a popup camper the longest ( i know you cant be exact without knowing how much is running), by wiring 2 6 volt golf cart batteries together to make the 12 volts or 2 12 volt deep cell batteries for the more amps? i also have and want to use a 45 watt ( and poss buying more) solar charger. which way is better

    Reply  •  January 20, 2013 at 6:22 pm
    • BatteryStuff Tech
      If your system is 12 volts, then I recommend the option with the highest capacity (as you said, that would be the 2 12 volt deep cell batteries for the more amps).

      Reply  •  January 21, 2013 at 9:14 am
  • Richard
    Hello, I have a 24V bank consisting of 12 Trojan T105‘s. After about 4 years one or more of the 6V batteries will come up with a bad cell.I understand that it is not practical to replace a singe battery, but it drives me crazy to replace the entire bank when some of the batteries appear to be just fine. I am thinking of going to a single string of 12, 2V batteries this time. My thinking is that I will then be able to replace an individual 2V battery because nothing will be in parallel. Does this make sense?

    Reply  •  January 19, 2013 at 8:05 am
    • BatteryStuff Tech
      A bank of 2 volt cells is more efficient and a good idea if you‘re starting from scratch.

      Reply  •  January 21, 2013 at 9:11 am
  • Dave
    hi there, i‘ve been toying with the idea of making a portable power pack for a 12V system main use for an airconditioning unit. Is this scenario possible? if not what would the problems be… a 12V battery, an Air Con compressor and a high output alternator/generator, all running off one fan belt. what are the tech specs needed for alt and motor? i.e. is it possible to charge a battery while drawing power from it??. 12v motors are becoming efficient and alternators are becoming more high capacity ie 110amps etc. is it possible? even doubling up alternators, example running 2 at 220amps of the same driven motor?

    Reply  •  January 18, 2013 at 7:20 pm
    • BatteryStuff Tech
      I fail to see how these questions are related to the article. Please email us for such highly technical questions.

      Reply  •  January 21, 2013 at 9:01 am
  • Terry
    I have an EV that uses six 12v AGM batteries in series to provide 72 volts to operate the vehicle. If I hook up a 30amp stereo system across one of the 12 volt batteries, would it work? Would there be any negative electronic repercussions? Is there a better way to do this?
    Thanks for any Help!

    Reply  •  January 18, 2013 at 6:08 am
    • BatteryStuff Tech
      That is not recommended. You will cause an imbalance in the battery bank. If the battery bank is being used to run the vehicle, and then you also try to use one battery isolated, it will not work. Please consider a step down dc to dc converter as a solution to your problem.

      Reply  •  January 18, 2013 at 9:20 am
  • Daniel
    Ok i was just wonderin i have 4 12 volt 800 amp batteris ran in parallel and in series so added up toghter it us 24 volt and 1600 amps right? And i was just wondering if a stock alternator that is 12 volt would charge them and where would i hook it up..

    Reply  •  January 17, 2013 at 2:03 pm
    • BatteryStuff Tech
      Voltage and Capacity both increase, yes. I assume the amps you are referring to are Cold Cranking Amps (not Amp Hours). A 12 volt alternator will be able to charge the batteries if they are in a series configuration.

      Reply  •  January 17, 2013 at 2:38 pm
      • Daniel
        Ok so it would charge them even if they are ran both in a series and parllel. And yes that is the cold cranking amps not amp hours

        Reply  •  January 17, 2013 at 3:49 pm
        • BatteryStuff Tech
          Sorry, a missed word on my original comment. The 12 volt alternator will NOT be able to charge your battery system if you have the batteries connected in series. But if all 4 were in parallel, then it is possible.

          Reply  •  January 17, 2013 at 3:55 pm
          • Daniel
            Ok..lets say i have them hooked up both ways how would i be able to charge them if there is a way..because im trying to improve both my volts and amphours (which is 36AH a battery) because what im running works better at 15 volts and i was going to put a volt regulator in between to run at 15

            Reply  •  January 17, 2013 at 4:09 pm
            • BatteryStuff Tech
              Even though you have a parallel connection, because you have a series of 24 volts, the 12 volt alternator cannot fully charge the entire bank. And we do not recommend connecting your alternator to a partial part of your battery bank, instead of the entire thing.

              May I suggest using a 16 volt battery and system, like the ones used in racing applications?

              Reply  •  January 17, 2013 at 4:31 pm
              • Daniel
                Ok that sounds good but lets say i dont run it from my alternator but have them hooked up in a series and parellel could i use a battery bank charger to keep them charged

                Reply  •  January 18, 2013 at 3:42 pm
                • BatteryStuff Tech
                  Yes, if you find a multi-bank charger than can hook up to each battery in the system, it will work. Four 12v outputs is what you should look for, but technically 2 will work if you connect each bank to a pair of batteries paralleled to each other.

                  Reply  •  January 21, 2013 at 8:59 am
  • Gm
    What will happen if I connect 12v 18 amp paralell with 12v 30 amp ?

    Reply  •  Rated article 1  •  January 15, 2013 at 10:48 am
    • BatteryStuff Tech
      The larger capacity battery will feed into the lesser capacity battery as part of electricity‘s attempt to ‘equalize’. This results in one battery being discharged more than the other, and imbalance will cause early failure in one or both batteries.

      Reply  •  January 15, 2013 at 12:07 pm
  • Richard Hodgson
    i want to charge a 18v Dc NiCd power drill battery using two 12v DC 100 AH lead acid batteries connected in parallel and which are charged using 12v solar panels. How can this be done. If I temporarily re-connect the two 12 volt batteries in series to get an output of 24v, is this too high a voltage to be connected direct to the 18v NiCd battery terminals to charge it satisfactorily.

    Reply  •  Rated article 5  •  January 15, 2013 at 10:09 am
    • BatteryStuff Tech
      We don‘t recommend what you intend to do. 12v is too little to charge, and 24v is too much. Also, it‘s not a good idea to connect batteries of different chemistries together.

      Reply  •  January 15, 2013 at 10:11 am
  • Ibnu Mulkan
    i have a winston battery from china, in the brochure i found that the battery have operation voltage with charge is 4Volt and discharge is 2.8 volt.. what mean of that? second is how i configure this battery to get 12Volt ,, what voltage do i choose?(4Volt or 2.8Volt)

    Reply  •  January 14, 2013 at 7:42 pm
    • BatteryStuff Tech
      It sounds to me like your battery should read at least 4 volts and it will be considered fully charged. But if your resting voltage reading is 2.8 volts or less, then the battery is discharged and needs to be re-charged. You can wire 3 of these batteries in series to obtain 12 volts.

      Reply  •  January 15, 2013 at 9:18 am
  • Gary
    I‘m looking for some recommendations for setting up a small camper on solar. I have two 260w panels for 24v and a MS 45w mppt charge controller which will work for charging 12, 24, 48v batteries. The camper will be placed off grid in SoCal where the sun is good. What battery configuration will give me the best performance with these panels? Will be running rv fridge on 110 and a few cfl lights, laptop, led tv, dvd player. The trailer currently has two 6 volt batteries connected to a progressive dynamics 9200 controller that is more than adequate for the 12 volt system already on board when charged by shore power. So the idea is to have a solar system set up as a separate solar generator an a small seperate trailer that I can plug the camper into since I will not have shore power. Hoping to keep the 110v stuff working when needed and charge the on board 12v system. Also need to consider a PSW inverter. Any ideas on this set up?

    Reply  •  January 13, 2013 at 3:39 pm
    • BatteryStuff Tech
      Please use our solar calculator for your system. I also suggest finding the power ratings on all devices that will in the system (fridge, lights, etc.). This should determine the size your battery bank should be, not how much solar you have.

      Reply  •  January 14, 2013 at 10:39 am
  • Matthew
    i have a boat with a two bank system. the “starting” bank is a group 27 deep cycle wet cell battery, the “house” bank is 2, group 31 batteries wired in parallel. would there be any reason why i can‘t get the “house” bank to charge up fully? i have them all hooked up to a 20Amp marine charger.

    Reply  •  Rated article 5  •  January 10, 2013 at 6:03 pm
    • BatteryStuff Tech
      The house bank is considerably larger capacity than the starting bank. Are you letting your charger go through a full charge cycle? If they‘re not charging fully, can you provide a current resting voltage reading to determine state of charge?

      Reply  •  January 11, 2013 at 8:55 am
  • John
    I have an electric bike that has 3 12 volt 7 amp batteries and range is an issue. I want to buy 3 12 volt 12 amp batteries for a total of 6 in all, hook them up parallel to keep my 36 volt current. my goal is to extend the range of the motor and bike. Can I use to the two sets of battery‘s together or should I mix them or what? Also how would it impact my amp rating?

    Reply  •  January 8, 2013 at 4:09 pm
    • BatteryStuff Tech
      It‘s important that you keep the 36 volts. Your range will increase if your capacity increases. More Amp Hours will do this. If you use 12 AH batteries instead of 7 AH batteries, then it will work. I don‘t recommend using both. For any battery system, all batteries should be the same voltage and capacity. It‘s not recommended to mix and match.

      Reply  •  January 9, 2013 at 8:39 am
  • Justin
    I want to hook up 6 12v batteries and make them come out 48v how do i do that

    Reply  •  January 7, 2013 at 5:12 pm
    • BatteryStuff Tech
      We recommend having an even and balanced battery bank. Therefore, you should only use 4 of the batteries, or buy 2 more for 8 in total.

      Reply  •  January 8, 2013 at 9:22 am
  • Gpeg
    Hi, great service you are providing here. I have an EV with a 72 volt system comprised of 6 12 volt 100 AH deep cycle batteries wired in series. Is there any advantage to changing the wiring from series only to the combination you suggest? What would my theoretical AH rating become? Thanks, and Happy New Year

    Reply  •  Rated article 1  •  December 31, 2012 at 9:30 pm
    • BatteryStuff Tech
      If you are referring to connecting your batteries in parallel, then your battery system will be 12 volts with 600 AH.

      Reply  •  January 2, 2013 at 9:57 am
  • John
    I made a survival power cart this past year, and I am glad I had it for Hurricane Sandy. Here is my parts list:
    -Plastic 3 shelf cart from Costco 99.00
    -3 125AH 12v deep cycle marine batteries from Walmart 250.00
    -1 Ramsond Sunray 3000, 12v pure sine wave inverter built in meter 500.00
    -2 Anderson connector sets for 4/0 wire 40.00
    -1 Heavy duty marine battery switch, internal sealed contacts 40.00
    -30’ of 4/0 xflex cable and lugs 250.00
    -1 heavy duty 200A fuse 60.00
    I keep the batteries float charged until they are needed. When the power goes out, I plug into the inverter and put the battery switch to on and I am up and running. I used the kill-a-watt meter to check all of my essential needs. Sump pump 500w, refrig 135w, hot water baseboard heat 150w, small tv and satellite box 100w, internet modem and router 80w, 60w CFFL bulbs 13w each. Before I see the volt meter on the inverter start to drop (the inverter shuts off at 10.5v)I plug the battery bank into my Chevy Tahoe that has a 8’ set of 4/0 cables attached to my battery with a Anderson connector on it. When the Tahoe runs it charges the batteries and powers what I need. During Hurricane Sandy, most gas stations didn‘t have power so I kept the Tahoe topped off with 5 gal gas cans I filled before the storm which carried me through 4 days until our power was restored. I was able to turn the vehicle on and off every few hours so it did not have to run continiously. I am planning to add 3 more 125A 12v batteries to my setup for longer runtime. This setup is quiet and when the Tahoe runs you cannot hear it in the house. My question is: Would I just need a 250W solar panel with a MPPT charger to charge my batteries if they were depleted to 10.5v and still have some power to run some of my “needs”?
    If you want to see my setup, go to (give me a few minutes to post the photos)

    Reply  •  December 30, 2012 at 8:23 pm
    • BatteryStuff Tech
      10.5v is considered completely discharged. If your total capacity is going to be 750 AH (6 × 125) then it will take 37.5 hours of direct sunlight for the 250 Watt solar panel to recharge your battery system. 250 Watts delivers up to 20 amps of charger per hour of direct sunlight.

      Reply  •  January 2, 2013 at 8:43 am
  • Sshresth01
    Is it possible to connect 100 Ah battery with 80 Ah battery in parallel both with 12 V? However, the batteries are of different companies?

    Reply  •  Rated article 5  •  December 27, 2012 at 8:46 am
    • BatteryStuff Tech
      Of course it‘s possible, but it‘s not ideal.

      Reply  •  December 28, 2012 at 9:00 am
  • Eb
    I have a single 12V powertron flooded battery on my sailboat connected to a 15W sunforce solar panel protected by a sunsaver 10 Ah 12volt controller

    This system powers an anchor light and bilge pump directly connected to the battery. It also serves to crank start a 9.9 outboard but this remains disconnected unless in use.

    Here is m problem, after several weeks of use, and not being checked on …the anchor light goes out and when checked, the battery has less than 2 volts per the mulitmeter.

    This is my second battery that this has happened with. the first one was with the 7amp sunforce controller that fialed so I bought the sunsaver and a new battery. now the battery is shot but the controller is still in good shape.

    this has me stumped and could really use some help

    merry Christmas


    Reply  •  December 25, 2012 at 12:05 pm
    • BatteryStuff Tech
      Although the controller may be rated for up to 10 amps, the 15 watt solar panel will only charge at roughly 1 amp per hour of direct sunlight. Maybe you need a larger solar panel?

      Reply  •  December 28, 2012 at 8:28 am
  • Michael
    Great article. I converted my diesel vehicle from 24v to 12v but have been running through 12v starters because they are not powerful enough to start the engine. I would like to install a 24v starter without having to replace all of the lights, accessories, and other components. Could I run two batteries in series to run the 24v starter while connecting the 12v lights and accessories to one of the batteries and using a battery isolator to charge both batteries from the 12v alternator? If this configuration won‘t work is there another that might?

    Reply  •  Rated article 5  •  December 24, 2012 at 12:40 am
    • BatteryStuff Tech
      Yes, your proposed setup will technically work. It‘s important to know that as one battery drains more than the other in series, the battery bank will try to equalize and you will see decrease capacity overall and possibly shortened battery life.

      Reply  •  December 28, 2012 at 10:42 am
  • Ahmadi
    I am in Afghanistan and want to make a 2 or a 5 KW AC power from battery bank.
    the solar panel which i can find here are 160W panels and 70amps up to 150amps battery, and my inverter (dc to ac) is need 12V DC.

    So can you tell me how to wire batteries and how many solar panels and so on. please.. thanks

    Reply  •  December 19, 2012 at 3:27 am
    • BatteryStuff Tech
      If you need 1 hour of 2 KW AC power, you will need a battery system with 12v and 350 AH (5 of the 70 amp batteries in parallel) and 2 of the 160 Watt solar panels in parallel (with 8 hours of sunlight to recharge). You will need a lot more batteries and solar panels if you need to run 2 KW for longer than 1 hour, or if you need more power such as 5 KW. Please use our solar calculator for your system recommendations.

      Reply  •  December 19, 2012 at 3:35 pm
  • Brett
    I have a truck camper and I want to wire a deep cycle marine battery to be run in parallel with the truck battery in order for the furnace to last longer on cold nights. Is this a bad idea?

    Reply  •  December 18, 2012 at 12:35 pm
    • BatteryStuff Tech
      In the event of urgency, it can be done. But we don‘t recommend it. A deep cycle battery and a starting battery do not discharge the same. You risk harming the starting battery under such a deep load as a furnace.

      Reply  •  December 18, 2012 at 12:51 pm
  • Matthew
    What happens if you want to wire a couple hundred or maybe thousands of lithium batteries (AA sized) to each other to get 24 volts and around 275 amps?

    Reply  •  Rated article 4  •  December 17, 2012 at 9:02 pm
    • BatteryStuff Tech
      If done correctly and carefully, you should have a 24v battery system with 275 Amps. The question is, what do you intend to use the batteries for?

      Reply  •  December 18, 2012 at 9:23 am
  • Musthafa
    If i connected 12v/50a battery with 3v/800ma, what is the output voltage and current?

    Reply  •  Rated article 1  •  December 17, 2012 at 7:50 pm
    • BatteryStuff Tech
      I‘m sorry, but we don‘t recommend connecting batteries of different voltages and capacity, especially with such a big difference in capacity. What is the power requirement of the application you wish to use this with?

      Reply  •  December 18, 2012 at 9:07 am
  • Arun
    I have 2 questions:
    1. Is connecting two sets of battery banks in series-parallel connection just a theoretical approach or there are some limitations?

    2. What happens if 4 batteries of variable ratings are joined in series parallel? I mean (1st battery)1V,1Ah +ve terminal of which is serially connected with negative terminal of (2nd battery)4V,4Ah which are in parallel to (2nd row 1st battery)2v, 2Ah +ve terminal of which is serially connected with negative terminal of (2nd row 2nd battery)3V,3Ah batteries.
    Does the 4V, 4Ah one back flow to 1V,1Ah directly or it will go through 3V and 2V ones first? And can we predict that the resultant output will be 5V,5Ah???

    Reply  •  Rated article 5  •  December 13, 2012 at 12:31 am
    • BatteryStuff Tech
      1) As long as the batteries are same type, size, voltage, capacity, etc, there is no limit to how many you can connect. But I hope you realize the bigger the battery you construct, the heavier duty the cables you will need to use because of such an increase of power.

      2) Batteries joined together of different voltages and/or capacities will attempt to equalize, resulting in one or both batteries being drained and/or the other battery being overcharged. Your proposed setup is not recommended.

      Reply  •  December 13, 2012 at 11:02 am
  • Ricky
    what is the benefit of running two 6 volts batteries at 110 amp hrs. in series instead of buying one 12 volt battery at 110 amp hours. You will just be spending more money on buying 2 batteries.

    Reply  •  December 4, 2012 at 9:29 pm
    • BatteryStuff Tech
      The advantage would be that because 6 volt batteries are smaller, they can be designed with stronger connections from cell to cell inside the battery. Large 12v batteries are already very heavy, and sometimes the internal bridges are made not as thick to save as much weight on the battery as possible.

      This may not be the case with every 12v battery manufacutre. But consider that two 6v batteries are heavier than a single 12v battery of the same capacity, there may be a reason for that other than the extra plastic case.

      Reply  •  December 5, 2012 at 8:29 am
  • Hugh
    I‘ve got 8 six volt batts in series to power a 48 volt inverter. I have a standby inverter I want to attach to the same bank…however, it requires a 24 volt input. Can I tap the 48 volt bank for 24 volts by cross-tying the first four in series (24 volts) withe the second 24 volt half. The series would remain through all 8 batts for the 48 volts and I would get a balanced 24 volts off the two sets of 4 batts hooked in series and tied parallel at the 24 volt stage….what do you think?

    Reply  •  December 4, 2012 at 4:17 pm
    • BatteryStuff Tech
      We do not recommend pulling different voltages from a single battery bank. Connecting eight 6v batteries in series and attempting to create a parallel connection of two 24v banks consisting of four 6v batteries at the same time could create a short circuit.

      If you need to run a 24v load, I suggest using a 48v to 24v step down converter. That way, the battery bank will always be drawn at 48 volts, but your load can be supplied by the proper voltage you need.

      Reply  •  December 5, 2012 at 9:02 am
  • Dennis
    I‘m replacing my batteries in my motorhome which had three 12v batteries. I purchased four 6v 230AH batteries if I connect these series/parallel can I come off from this for my main battery or should I use another 12v crank battery for my main battery?

    Reply  •  December 2, 2012 at 7:22 am
    • BatteryStuff Tech
      I cannot confirm if your bank of 6v batteries will be able to start your engine or not. Do your batteries have a CCA rating on them? This is the most common rating for starting purposes.

      Reply  •  December 3, 2012 at 9:00 am
  • Rick
    Hi, I have twelve 6 volt 225ah golf cart batteries and need to set it up as 24v bank for my inverter. What‘s the best way to wire this? Thank you!

    Reply  •  November 29, 2012 at 8:34 pm
    • BatteryStuff Tech
      Connect four of the 6 volt batteries in series. Do this for a total of 3 times. For all intents and purposes, you now have three 24v batteries, with only one open negative and positive post (on the ends of the string). Now connect these ‘three’ batteries in parallel by wiring together all of the positives to each other, 3 total, one from each battery, and do the same for all of the negative posts. You should have a 24v battery bank with 675 AH.

      Reply  •  November 30, 2012 at 8:28 am
  • John D.
    I have a bunch of questions:

    If I am going to connect a number of 12V batteries in parallel, do I have to worry about the batteries being slightly different models or brands? What about different amp-hour ratings?

    Can a bank of two 200Ah batteries be expanded with two more 230Ah batteries? Or do they have to match as exactly as possible?

    Reply  •  Rated article 4  •  November 28, 2012 at 2:36 pm
    • BatteryStuff Tech
      There should be caution when using batteries of different types, sizes, and brands. Because when connected in a bank, they will behave as a single unit. Having differences from one battery to another will cause the entire bank to be unbalanced. Technically, the bank will work but the unevenness will cause early failures from some batteries and the entire bank in general. It‘s not recommended.

      Reply  •  November 28, 2012 at 2:59 pm
  • Robert
    Hello, I‘m creating a 48volt solar system with 4 each 12volt deep cycle batteries (all the same aH). My question is, will my Solar array need to push out 50 plus volts to charge the battery bank or will the MMPT take care of this even if the array only delivers less than 48 volts?

    Reply  •  November 22, 2012 at 12:57 pm
    • BatteryStuff Tech
      If the output voltage drops below 48 volts, I suppose the MMPT can increase the output voltage to the proper level, with lowering the current as a result.

      Reply  •  November 26, 2012 at 1:08 pm
  • David
    understood, but can i hypothetically only add one 2v cell in parallel with one of the current 2v cells in the original bank to increase the capacity with that new cell?

    Reply  •  November 21, 2012 at 11:25 pm
    • BatteryStuff Tech
      If you have cells in series, but some of them are pairs in parallel, while others are not, you will experience uneven discharge and recharging because the bank behaves like a single unit. If any one part is off, it will effect overall performance and longevity. It‘s simply not best practice.

      Reply  •  November 26, 2012 at 12:52 pm
  • David
    i have a solar charging system with 24 X 2v cells in series to create a 48v feed to the victron unit. can i ad on more cells in parallel to some of the current cells to increase capacity but keep the 48 v intact?

    Reply  •  November 21, 2012 at 3:26 am
    • BatteryStuff Tech
      Yes, you would need 24 more cells in a series, and then parallel the two 48v banks to create a single 48v bank with twice the capacity.

      Reply  •  November 21, 2012 at 9:10 am
  • Ravindra
    how to connect two batteries so that I can get twice of backup of a single battery also the voltage and current should be the same as that of a single battery means I just want to double the backup nothing else.

    Reply  •  November 20, 2012 at 8:48 am
    • BatteryStuff Tech
      Amp Hours is your battery storage amount. It‘s the capacity of the battery. Parallel connections will double your Amp Hours, which doesn‘t increase your current/load amount, it gives you longer runtime for your system. Refer to the article for proper parallel connections.

      Reply  •  November 20, 2012 at 4:25 pm
      • Ravindra
        Thanks for your reply one more question is it safe to use two mobile batteries(connected in parallel) to obtain double battery backup for cell phone.

        Reply  •  Rated article 5  •  November 21, 2012 at 8:27 am
        • BatteryStuff Tech
          Yes, that should be fine.

          Reply  •  November 21, 2012 at 9:30 am
  • A.S.C.
    All alien language to me. I need to know if what I want built is possible. Someone with more knowledge than me will be doing the building. I need a bank of batteries which can take a small/medium RV off the grid AND be charged with a diesel generator, solar panels, truck electrical system (when truck is in operation), or from an ‘on the grid’ AC service. In addition, I would like to be able to hook in a solar generator to charge while the batteries are charging or charge from the batteries themselves. If something like this is possible, can it be carried safely in the bed of a super-duty pick up which also carries a dual gasoline/diesel transfer tank?

    Reply  •  November 20, 2012 at 8:44 am
    • BatteryStuff Tech
      Yes, it is possible to have a bank of batteries, solar panels, generator, and AC charger to make your RV off-grid. A lot of research regarding the demand and power needs would have to be done before anything can be recommended. Solar generators are nice to run your equipment, but it is inefficient to use one battery to charge another. It‘s possible, but inefficient.

      Reply  •  November 20, 2012 at 4:23 pm
      • A.S.C.
        Thank you. I really have no idea what I‘m [trying?] doing in this area. I will be embarking on a months-long motorcycle trek covering ten thousand plus miles in the spring and outfitting my support vehicle is proving daunting.

        Reply  •  November 22, 2012 at 6:56 am
  • Collin
    If you are running the four 6v batteries for the 12v output can you charge all four battery with one 12v charger? If yes I put 1 positive lead on the front row battery set and the negative lead on the back row set?

    Reply  •  Rated article 5  •  November 18, 2012 at 8:52 pm
    • BatteryStuff Tech
      Yes, you can use a 12v charger. Again, yes, your installation method is correct. Imagine the entire battery bank as a single unit, with only one true positive terminal, and one negative terminal.

      Reply  •  November 19, 2012 at 2:38 pm
  • Steve Heemsoth
    If I hook two 12V batteries in Parallel, I know that the CCA will increase. My question is: will this hurt any part of the electrical system to operate the vehicle this way with more amps running through it?

    Reply  •  November 18, 2012 at 9:45 am
    • BatteryStuff Tech
      If your application is starting an engine, more CCA will be good because it means your starter will have to work less to start. Having more CCA will not cause an overload, but simply more power available should the starter need it. If the application is running electronics and other deep cycle purposes, CCA is not even relevant. But AH (Amp Hours) will be helpful, again this simply means more capacity available which means longer runtime for electronics.

      Reply  •  November 19, 2012 at 2:36 pm
  • Nunyafb
    Hi i have 16 6 volt 125 amp/h hooked up as4 banks in series and the 4×4 in parallel but was told serpentine pattern is better which is how i have 6×6 traction batteries hooked up in that way but cant get my head around how to do it with these 6 volt batteries thank you

    Reply  •  November 14, 2012 at 10:53 pm
    • BatteryStuff Tech
      What is the total system voltage that you need?

      Reply  •  November 15, 2012 at 8:24 am
  • T.J
    all the articles are interesting but my question is wich is the best configaration for a 24 volt sola system 12×2volt batteries in parallel or 12×6volt in series & parallel both have the same potential amp hours hope to get a reply T.J

    Reply  •  November 9, 2012 at 10:41 am
    • BatteryStuff Tech
      If you had to choose between using 12 volt batteries or 6 volt batteries, I recommend using 6 volt batteries to obtain the voltage and capacity you need. We‘ve found that 6 volt batteries have cells that are constructed more durable, and there‘s less chance of open cell failures.

      Reply  •  November 9, 2012 at 12:07 pm
  • Dave D
    I bought 2 thunderbolt 45 watt solar systems from harbor freight, along with 3 of their 35ah batteries. I want to use the system to recharge my laptop, rechargeable batteries (AA), walkie talkies, etc. I have an inverter to convert to AC. Should I connect the batteries in parallel to maintain 12 volt but increase AH‘s?

    Reply  •  November 1, 2012 at 6:29 am
    • BatteryStuff Tech
      It depends entirely on the inverter. It‘s probably 120 VAC output, but what is the input? If it is 12 VDC, then parallel connections are recommended.

      Reply  •  November 1, 2012 at 8:43 am
  • Krishna
    I have UPS setup to which I have connected two battery banks of different ages in parallel. Each bank has 16 batteries connected in series .

    Bank 1 : one year old
    Bank 2 : purchased recently(less than 2 weeks old).
    All batteries are 12V , 26 AH and same company make, except the age.

    Initially with just just battery bank one I use to get backup time of 70minutes, with addition of second bank its hardly increased to 120min and sometimes its even less…

    I had a feeling that the second battery bank(newer one) is not being completely charged due to the first battery bank connected in parallel.

    Can you suggest me how to isolate the two battery banks during charging.

    Reply  •  October 31, 2012 at 11:38 pm
    • BatteryStuff Tech
      If you want to charge the second bank separately, I recommend disconnecting it from the first and charging accordingly. Otherwise, you can use a 2 bank charger, like the Dual Pro, which can charge two banks completely isolated from each other, but the parallel connections can remain.

      Reply  •  November 1, 2012 at 8:41 am
  • Greentech
    I have a variety of 12V batteries with different AmpHour capacities. I also have a solar/wind setup to charge them all with seperate charge controllers. I have setup a bus bar for them all to connect to. What I want to know, is can I have multiple groups of batteries of the same type/capacity together in parallel to the bus bar without causing a rapid drain from the banks with a much larger capacity than the other banks?

    i.e. I have 2 high capacity banks and want to be able to remove 1 bank, as well as charge multiple small capacity batteries for mobile use. Here is the typical setup ->

    Bank 1 – 3 AGM 180Ah batteries
    Bank 2 – 2 Gel 105Ah batteries – periodically removed
    Bank 3 – 1 Gel 15Ah battery – charged, then removed
    Bank 4 – 1 Gel 7.5Ah battery – charged, then removed

    All of these are then connected to the bus bar simultaneously.

    Will this be ok, will I need diodes?

    Reply  •  Rated article 5  •  October 29, 2012 at 8:58 am
    • BatteryStuff Tech
      If all the batteries on the bus bar are the same size and type, and your connections are all in parallel, then there should be no problem as far as one bus bank having more batteries than the other. The problem lies in the issue if the batteries are at different discharge levels and that will cause the batteries to equalize and resulting unevenness of charging. I do not recommend having Gel and AGM batteries together on the bus bar at the same time.

      Reply  •  October 29, 2012 at 10:37 am
      • Greentech
        What I mean by the different banks, highlighted above, is that they are wired in parallel and are all of the same type. The different banks are then connected to a common bus bar, effectively making further parallel connections. So would this result in back-flow from the bigger bank into the smaller bank and put added strain on the cables as well as the batteries?

        What I want to achieve is charging from a single source, and an inverter to be able to draw current from all of the banks. Can this only be achieved by a complex matrix of diodes?

        Reply  •  Rated article 5  •  October 30, 2012 at 5:18 am
        • BatteryStuff Tech
          Yes, if the different banks are connected to a common bus bar, and they are discharged more than other banks, there will be back flow.

          Reply  •  October 30, 2012 at 8:23 am
  • Mike
    Charging 12/24V system? we have a total of 6 identical 12V batteries, paralleled in banks of 3 equalling two 12V sources and we have them in series only for the purpose of charging them with a 24V solar panel that we had on hand. Is this a sufficient charging method given that that 12V banks serve different loads and have different discharge rates? or do we need to order some 12V solar panels?

    Reply  •  October 27, 2012 at 3:17 pm
    • BatteryStuff Tech
      Because one bank is being discharged more than the other, and they are both being connected as a single 24 volt unit, you will experience an unevenness of charging. The lesser charged batteries will act as a load to the other bank because the batteries will slowly attempt to equalize. But if your one bank will be consistently used time and time again, you will find that charging with the solar panel will prove inefficient as it will prove difficult for either bank to reach full charge unless you allow the batteries to become equal in state of charge.

      Reply  •  October 29, 2012 at 9:17 am
  • John
    i have begun compiling the componants for an electric vehicle. it is to be a 144 volt system. i have 12, 12 volt deep cycle sealed agm batteries that are aprox 140 amp hrs. ea. ( they weigh 100 lbs. ea.! ) i also have purchased; ( something that i have not seen ANYWHERE, as has no one else that i know.! ) weird. it is a battery charger made for a motor pool 12 volt vehicle charging. it has 12 individual, + & – cables to treat each battery individually in the pack. it monitors them in groups of 2. charging 14, floating 2 upon full charge. my question is this: can i build a solar array that will operate this charger? i have a 12volt to 120 volt 1000 watt digital inverter and a solar controll modual…wondering.

    Reply  •  October 25, 2012 at 11:38 pm
    • BatteryStuff Tech
      If your 12 bank battery charger runs on 120 VAC, then it will be difficult because Solar Panels are rated for 12 volts. I would recommend using a solar panel to charge a 12 volt battery, to power your inverter, which can be used to plug in your charger, to charge your large bank of batteries. I‘m sure where you can see the inefficiencies in this scenario.

      It will be much simpler to buy a solar panel(s) to charge your batteries directly, not to power your AC charger.

      Reply  •  October 26, 2012 at 8:30 am
  • Lee
    I have a 24 volt battery bank with a wind turbine,but I want to use a 12 volt power inverter.What would I need to do so the feed to the inverter is stepped down to 12 volts? I found your tread very informative

    Reply  •  Rated article 5  •  October 23, 2012 at 7:17 am
    • BatteryStuff Tech
      A 24 to 12 volt step down converter would help. Or you can use a 24 volt power inverter for better efficiency. The ratings for these devices depend entirely on the load amount drawn on the batteries.

      Reply  •  October 23, 2012 at 10:53 am
  • Gautam Patel
    I have Manlifter with eight number of batteries 6V,375Ah,Now one battery was not charged and I want to replaced by only one now battery out of eight batteries.Kindly be advice me is it possible to replace only one battery from battery bank.

    Reply  •  October 16, 2012 at 3:33 am
    • BatteryStuff Tech
      Of course it‘s possible to buy one new battery and put it into your existing bank. It‘s not recommended because different age batteries will charge and discharge at different rates, and will lead to overall shortened battery bank life when compared to a configuration with batteries of the same age.

      Reply  •  October 16, 2012 at 10:21 am
  • MuNa
    Shall I use 20ah battery instead of 8 ah battery in pc ups?

    Reply  •  Rated article 5  •  October 15, 2012 at 9:52 am
    • Marine57
      “Shall I use 20ah battery instead of 8 ah battery in pc ups?”

      Probably not – because it depends upon the design of the charge/discharge electronics in the UPC as to whether or not it will recognize the extra power available in the larger capacity battery.

      The 1500-VA Geek Squad UPC I am using is undergoing tests right now (2-21-2013). Using the HR9-12, 12V,36 WPC/15 min specified batteries, the UPC ran my PC for 32 minutes avg. With 2-ETX9, 120 CCAmp motorcycle batteries, that probably have twice the capacity in Watt-Hours (to be determined later by tests) the UPC ran my PC for only 20 minutes. The 12v batteries should last until its voltage drops to 10 volts. However, the UPS quits when the batteries have dropped to only 11.29 – using an estimated 50% of the battery‘s actual capacity.

      The UPC estimations of remaining time before shut-down are ridiculously poor and inconsistent from run to run. At this time, I suppose that how long the UPC can operate the PC pertains more to it‘s ability to output the PC‘s load without overheating its electronics more-so than what the batteries can supply over time. I am quite disappointed with the UPC‘s design at this time (not its life span – the Geek Squad unit is doing better than I have ever seen in a UPS.

      Reply  •  Rated article 4  •  February 20, 2013 at 9:59 pm
    • BatteryStuff Tech
      That‘s entirely up to you. A battery with more AH simply means that you will have a longer runtime for your application before needing to recharge the battery again.

      Reply  •  October 15, 2012 at 11:37 am
  • Geoff

    I am wondering if I can use a 12 V alternator to charge a 48 V battery bank. Could the 12 V alternator connect to a step-up transformer to do this? Assuming it could, would the alternator‘s output then drop by an quivalent ratio? i.e. if I step up voltage 4X, do I step down amperage 4X?

    Reply  •  October 7, 2012 at 12:57 pm
    • BatteryStuff Tech
      You are correct, as the voltage increases the amperage will decrease in order to maintain the same total power. Not only that, there will be an efficiency loss when using the step up converter. The best way to charge a 48 volt bank is with a 48 volt charger.

      Reply  •  October 8, 2012 at 9:10 am
  • Tc
    I am helping a friend with a problem. He set a solar charging system for 3 12v 690amp deep cycle batteries from Kragen. They are hooked parallel. He has 6 15 watt harbor freight solar panels parallel. Then it runs to a inverter to power a 115v .9amp pump

    He told me that he is getting 20volts going to 3 batteries, the batteries still show about 11.8.

    So it sounds like the batteries aren‘t fully charging.
    Any ideas?

    Reply  •  Rated article 5  •  October 3, 2012 at 8:40 am
    • BatteryStuff Tech
      I recommend using a controller to regulate the voltage to a safe ~14.6 volts instead of 20. 11.8 volts is still discharged, probably if the batteries aren‘t rising in charge it may be due to sulfation build up. If they are flooded batteries, have you tried getting a Specific Gravity using a hydrometer? This will determine the health of the electrolyte.

      Reply  •  October 3, 2012 at 8:49 am
      • Tc
        I haven‘t looked at them. I came across this site(very good) and wanted a few pointers before I looked at them. This is a new system that he set up.

        the batteries he bought from Oreillys/kragen are the
        Super Start® Marine – Deep Cycle Battery
        Part Number: 31DCM

        Reply  •  Rated article 5  •  October 3, 2012 at 9:03 am
        • Tc
          I forgot to add

          Thank you for the help.

          Reply  •  October 3, 2012 at 11:02 am
  • Tc
    If I hook 3 12v batteries in parallel is it a good idea to tie feed from the negative on battery #1 and the positive on #3?

    Reply  •  Rated article 5  •  October 2, 2012 at 9:39 pm
    • BatteryStuff Tech
      Yes. By doing so, the current will flow evenly through the entire string of batteries. This will be more efficient than if connecting both cables on a single battery, which will technically works as well.

      Reply  •  October 3, 2012 at 8:09 am
      • Tc
        Thanks. It confirms what I was thinking

        Reply  •  Rated article 5  •  October 3, 2012 at 8:19 am
  • JD
    can i connect 8 batteries in series parallel for 12v? in says in diagram that any number should be possible but wanted to ask the tech to double chech.

    i have a hydro wheel that produces 25amps @ 12v. my expanded battery bank is now going to be huge with 8 L16 6v 600ah batteries. even though input is constant we do draw the system to 60% at least weekly through heavy use of air heater/power tools/laundry. is series/parrallel the optimum setup for this type of deep cycling? we have a very nice new tristar morningstar charge/diverson control.

    Reply  •  October 1, 2012 at 1:37 pm
    • StoneEdge
      Yes, you can connect eight 6 volt batteries in a series parallel configuration to give you a 12 volt system. Best performance will be achieved using less batteries, so theoretically, if you can use 12 volt batteries instead of 6 volts, that would be better.

      Reply  •  October 1, 2012 at 3:15 pm
    • StoneEdge
      Yes, you can connect eight 6 volt batteries in a series parallel configuration to give you a 12 volt system. Best performance will be achieved using less batteries, so theoretically, if you can use 12 volt batteries instead of 6 volts, that would be better.

      Reply  •  October 1, 2012 at 3:03 pm
  • Gordon
    I have a 24 volt solar system, can I hook up two 6 volt and one 12 volt to get the 24? Two batteries are Trojan and the 12 volt is a gel battery.

    Reply  •  October 1, 2012 at 12:38 pm
    • StoneEdge
      Technically speaking, yes you can do that. We don‘t recommend it. As we state in the article, we don‘t recommend creating a battery bank with batteries of different types and voltages, as this will create an imbalance of discharge and re-charge, leading to premature battery failure.

      Reply  •  October 1, 2012 at 2:59 pm
  • Sandor Szabo
    Congratulations for this site!
    I use 6 cell 2300 mAh LiFe battery packs with cells connected serial to get 21,6 V. I use 2 pcs of such packs in parallel to get 4600 mAh with the same voltage.
    Recently I have noticed that one of the pack discharges more than the other and it also warms up significantly, while the other one has a normal working temperature and it discharges unusally less.
    I drive an RC helicopter with them. Normally with 5,5 minute flying time both packs charges about 1400 mAh, and now the hot one gets 2000 mAh, the colder only 1000 mAh. Normally both packs discharges 1500 mAh.
    My questions are: Which pack has a bad cell? The one which is overheated and discharges deeply or the one which does not have high temperature and discharges less then normally.
    Thank you.

    Reply  •  September 28, 2012 at 2:16 am
    • BatteryStuff Tech
      The pack that overheats and discharges more should be the bad one. Healthy batteries should not heat up, usually that‘s caused by in increase in internal resistance, which happens to older batteries. Are the battery packs the same age?

      Reply  •  September 28, 2012 at 8:36 am
      • Frank Niezgoda
        I have 2 12 volt AGM 4D deep cycle batteries wired in series to power my 24 volt trolling motor. Is it safe to run 12 volt appliances off of one of the batteries

        Reply  •  Rated article 5  •  October 1, 2012 at 7:08 am
        • BatteryStuff Tech
          It is not safe to run a 12 volt application at the same time if your batteries are powering the 24 volt motor. But yes, you can connect to a single battery and use it without having to disconnect your batteries from each other. But discharging one battery will cause an imbalance in your battery bank, and premature failure as one battery will not last as long as the other.

          Reply  •  October 1, 2012 at 10:21 am
      • Sandor Szabo
        Thank you for the answer. The age of both packs are 2 years and have not more than 40 charging cycles. I disassambled the pack and I noticed that the cells are soldered together. That process probably could damage the cells by the too high heat.
        Does it help if I reconfigure my good packs?
        Currently I use 6 cells in serial and two of this pack in parallel.
        What do you think of a configuration of making a pack with 2 cell parallel and 3 of them in serial. I would get a 9,9 V pack and I would connect two of such packs in serial?

        Thank you for your assistance.

        best regards

        Sándor Szabó

        Reply  •  September 29, 2012 at 12:42 pm
        • BatteryStuff Tech
          Unless you consider replacing all of the cells, it‘s going to be hard to determine which ones are bad (if any) and rearranging them to get 9.9 volt packs in series will only give you 19.8 volts, which is less than the 21.6 volts you stated earlier as your system voltage.

          Reply  •  October 1, 2012 at 11:05 am
  • Jodey
    i have a -1.5v, and a -4.5v, and a -9v battery. i need to add these 2 different ways to equal -4.5v. help me please?

    Reply  •  September 27, 2012 at 7:05 pm
    • BatteryStuff Tech
      For a system of 4.5 volts, you can attain this by paralleling batteries that are already rated for 4.5 volts. Or you can series batteries to create 4.5 volts, but we recommend using the same battery size each time. For instance, three 1.5 volt batteries in series will give you 4.5 volts. There is no safe method for using the 9 volt battery to create a 4.5 volt system.

      Reply  •  September 28, 2012 at 8:14 am
  • Chris
    I am wiring two 12v marine deep cycle batteries in series to provide 24v to some high powered LED lights on a boat. Two questions; (1) will I experience any problems using one group 24 battery and one group 27. (2) If the two batteries are wired in series, is there a way to make a connection to just one of the batteries to supply 12v to a second load? If so, how? Thank you!

    Reply  •  September 22, 2012 at 11:25 pm
    • BatteryStuff Tech
      Wiring in series batteries of different capacities will cause an uneven discharge of the batteries. They will try to equalize, and you will find one battery will fail sooner than the other. Also, if you need a 12 volt source, you simply need to connect to the terminals of a single battery. But you can‘t have both 12 and 24 systems running at the same time, it‘s either one or the other. Again, you‘ll have trouble with an uneven discharge of the batteries.

      Reply  •  September 24, 2012 at 9:43 am
  • Dean
    I was wondering since I have 4 deep cycle RV batteries connected in parallel where do i hook up the battery charger clamps..can i put them on one battery or do they need to be on two seperate batteries…

    Reply  •  September 22, 2012 at 6:33 pm
    • BatteryStuff Tech
      If you connect the clamps to a single battery, the voltage will carry through without a problem, but the amperage will decease as it passes cell to cell, battery to battery. But if you connect to the positive terminal of one battery on one end, and the negative of another, the charge will be more even. Both will technically work, but one is more efficient than the other.

      Reply  •  September 24, 2012 at 9:39 am
  • Dante
    Hi, can i connect a battery to my car ( in parallel ) while i‘m driving,and recharge my battery?

    Reply  •  Rated article 4  •  August 29, 2012 at 10:42 am
    • BatteryStuff Tech
      While this will technically work, it‘s not recommended if the two batteries are different sizes, types, capacities, and ages. When in parallel, they will act as one and try to balance out. One may be overcharged, and the other undercharged. The proper method to charge two batteries from a single alternator is to use a battery isolator. This enables you to charge both batteries, while keeping them electrically isolated from one another.

      Reply  •  August 29, 2012 at 11:16 am
  • Kelvin
    I have a 48v Inverter powered by 4, 200 ah deepcycle batteries of 12v each. The batteries are connected in series. I am not a technical person but i am looking for a way of having more hours on the inverter by using a parallel connection. If i buy a 12v inverter and use a parallel connection can i achieve that? What are the implications? Will i have to reduce the number of appliances on the Inverter because the volts will drop from 48 to 12?

    Reply  •  August 25, 2012 at 7:09 pm
    • BatteryStuff Tech
      If you have an application that runs off 115 VAC with a 2 amp draw, that translates to roughly 230 Watts. This is the total amount of power your application requires to run. Using OHM‘s Law, if you decrease the voltage, the amperage has to increase to maintain the same amount of power. Therefore, if you need 230 watts of power, you can take it (through an inverter) from a 48 volt source at 4.8 amps. (48 × 4.8 = 230) If you decide to use a 12 volt source instead, then your current draw jumps to 19.2 amps. If you ratio your draw to the total capacity of your battery systems, (48 volt) 4.8 amps : 200 AH and (12 volt) 19.2 amps : 800 AH, you will find that the ratios of current taken to capacity is the same for both. But because the jump from 48 to 115 volts is less work than from 12 to 115, the 48 volt system will prove more efficient simply because the inverter has less work to do.

      Reply  •  August 27, 2012 at 10:21 am
  • Jesse
    I thought if you hooked up 4-6 volt/10 AH batteries in series parallel, you would end up with 24 volts and 20 AH, not 12 volts and 20 AH?

    I need to design a battery system for a marine gas turbine project, it will run 12 volt accessories and need 24 volt only for the start cycle which will be considerable at about 500 amps for 30 seconds, what do you reccommend? 2-12 volts or 4 6 volts?

    I would like to run a 12 volt alternator and how would I hook it up to insure both batteries will be charged equally?


    Reply  •  Rated article 3  •  August 14, 2012 at 8:57 pm
    • Jeremy Fear
      Parallel, which is possitive to possitive AND negative to negative, will increase amperage and will not effect voltage. If you hook four 6 volt batteries in series however, (series is one possitive to the next batteries negative and so on leaving one ‘open’ possitive and one ‘open negative) then you will increase voltage and will not effect amperage.

      If you need your four 6 volt batteries to end up at 12 volts and 20 AH, then you will need a series/parallel system. You would seperate the batteries into pairs, and hook each pair in series (connecting the possitive of one to the negative of the other). Then, you would connect the ‘open’ (meaning the one not connected to the opposite polarity of the next battery) possitive of one pair, to the matching open possitive of the second pair, and you would do the same with the negatives.

      As far as your specific application goes, the correct method to take would be to use a converter to drop down the voltage from 24VDC to 12VDC for your 12 volt applications, while leaving the 24 volts for the motor. On a side note if you have four 6 volt 10AH batteries your application will not work well nor for long. We would recommend significanly higher capacity for that kind of application. For further technical assistance for your specific issue, you can email Thanks :)

      Reply  •  August 15, 2012 at 11:23 am
  • Ja.robby
    how do i connect four 6volts 225ah batteries so that
    i can get 24volts with or without increasing the ah.

    Reply  •  July 29, 2012 at 9:53 am
    • BatteryStuff Tech
      With four 6 volt batteries, please connect them in a string, connecting positive to negative from one to another. This will increase the voltage, but not capacity. The entire bank should still be 225 AH.

      Reply  •  July 30, 2012 at 9:11 am
  • Jarobby
    These are very good and important information i like it.

    Reply  •  July 29, 2012 at 9:33 am
  • Bob T
    I installed 4 new Batteries, initial charge looked good, it now appears one or more Batteries do not maintain charge and keep drawing current at rest,
    How do I find the faulty Battery?

    Reply  •  July 24, 2012 at 4:46 pm
    • BatteryStuff Tech
      I recommend you measure the voltage from each battery, and see where the difference is. If one battery is heavily sulfated and discharges quickly, it will also bring down the other batteries in an attempt to equalize charge across the entire bank.

      Reply  •  July 25, 2012 at 8:28 am
      • Pam Spencer
        Battery matching. In a perfect world. All equal. I tried to check all the batteries that I was buying and they seemed pretty equal. One is .2v not so much. Is that acceptable? My old batteries were showing 12.7 after charging. New ones with the lazy one 12.6 and goes to 12.5 too quickly. Winters comming and im not sure if I should get a new one or try a new set. 4 12v 1400 CCA lead acid truck starting with a 12v compressor refridge.

        Reply  •  Rated article 4  •  September 18, 2014 at 7:32 am
  • Jim Mitchell
    I have just purchase a boat that has 12 6volt batteries for the “house”. Does this setup seem connected right? There are 2 rows of batteries 6 in each. In the first row all + are connected together and all the – are connected to the + in the other row. Which leaves all the – in the second row connected together.

    Reply  •  June 28, 2012 at 2:11 pm
    • BatteryStuff Tech
      Yes, that sounds right. When the + is connected to the – across the row, they become a “single” 12 volt battery. When these pairs are wired together with ++ and — (parallel), they keep the same voltage but now you have more capacity. The entire bank is treated as a single 12 volt battery. Therefore, you only need to connect to one positive terminal from any of the bateries on one row, and one negative terminal on the other row. Do not use the terminals inbetween the pairs of 6 volts. Only use the outside terminals, only two needed, one + and one -.

      Reply  •  June 28, 2012 at 2:50 pm
  • Mike
    I have a new RV that uses 4 6 volt batteries in series – parallel to provide the 12 volts to various systems on the coach including an inverter for the house hold refrigerator. My query concerns the proper battery tender for this set-up. What tender set-up should be used during periods of RV storage so that the batteries remain charged and do not sulphate?

    Reply  •  Rated article 5  •  June 17, 2012 at 1:38 pm
    • BatteryStuff Tech
      For maintenance and storage, we recommend picking a charger at least 2-3% of the capacity of the battery bank. Usually this is an AH (Amp Hours) rating. So, if your 6 volt battery is 240 AH, then the entire setup is 12 volts, 480 AH. Therefore, I recommend a 12 volt, 15 amp charger. Less than 2% will cause the charger to overheat and struggle against the large self-discharge of the batteries. It would prove ineffective.

      Reply  •  June 18, 2012 at 9:27 am
  • Will
    Currently have two identical LiFE batteries wired in series to power a small transmitter. On the same rig are servos that can run happily off the voltage of one of the batteries, and draw very little current. Would it be dangerous to run a cable in parallel off of the jumper cable connecting the batteries together? It seems like it could lead to a slight voltage imbalance between the two batteries, how significant is that?

    Reply  •  June 11, 2012 at 6:54 am
    • BatteryStuff Tech
      Running a wire from the middle of the parallel wires will work. As long as the gauge is high enough so that the cable can handle the load you should be fine. Bus bars do this same thing, as there can be many applications all connected to a single battery source, and the wires can be very messy without any sort of organized arrangement.

      Reply  •  June 12, 2012 at 12:22 pm
  • Mark
    Is it possible to connect 5 batterys in parallel and the make a series connection to a bank of one battery just to increase the voltage? For example, if I have 6 6V 220ah batterys and want to create a 12V 1100ah bank.

    Reply  •  June 7, 2012 at 6:54 am
    • BatteryStuff Tech
      No, we strongly advise against a setup like that. If you need 12 volts, there has to be another battery to pair up with each 6 volts in parallel. Charge and discharge should be even. What you explained would be the equivalent of connecting a motorcycle battery to a AA battery, and hoping to utilize the combined voltage. The ration would be uneven, and it‘s dangerous for the smaller side.

      I don‘t mean to burst your bubble, but you‘ll need more batteries to achieve your system.

      Reply  •  June 7, 2012 at 8:41 am
      • Michael
        So just my 2 cents you would need 12 batteries for a system like that to work right?

        Reply  •  January 25, 2013 at 10:42 pm
        • BatteryStuff Tech
          Only 10 batteries are needed. Each 6 volt battery is 220 AH. 5 times this capacity (parallel) will give you a total of 6 volts, 1,100 AH. In order to get 12 volts with 1,100 AH you need another string of 5 batteries (again in parallel) and then connect these two strings in series to each other (only one cable needed between strings).

          Reply  •  January 28, 2013 at 9:10 am
          • Duong
            Another possible way to make a 12v-1100Ah battery out of ten 6v-220Ah batteries is connecting five of (two batteries in series) in parallel. Which way is better for a last-longing 12v-1100Ah battery, Tech? thank you

            Reply  •  February 20, 2013 at 3:04 pm
            • Vigneshwar
              if connecting 2 batteries in parallel it will get fast charge compare to serial connection ???

              Reply  •  Rated article 3  •  September 11, 2014 at 10:38 pm
              • TECH
                Optimal charging is 10% of the amp/hour of your battery pack. By going in series your amp/hour will be less, however your voltage will be more, and your will need to get a higher voltage charger. It is best to charge the batteries in the system voltage they are normally in and size your charger accordingly.

                Reply  •  Rated article 5  •  September 25, 2014 at 10:30 am
            • BatteryStuff Tech
              For a ‘longer lasting battery bank’ it makes no difference. More wire doesn‘t equal better performance. As long as the cable is strong enough, electricity doesn‘t know the difference. 12 volts is 12 volts, however you connect your batteries to achieve that power.

              Reply  •  February 20, 2013 at 4:20 pm
              • Chris
                I have a 18 – 6 volt battery system with each battery 232 Ah with every 2 batteries hooked in series and then all hooked in parallel. I am using heavy gauge welding cable for my connections . So my total amperage is 2088 Ah’s. I want to change this to 48 volts as I am increasing the size of my panels from 250 watts on 12 volts to 760 on 48 volts . The welding cable should be able to do job with no worries?

                I have to change power invertors also. Can a power invertor on input side be 48 volts DC and put out to the house 120 volts AC.

                Reply  •  February 24, 2014 at 6:39 am
                • Greg
                  Sorry, but I am a complete novice, so take the info only with self-checking for accuracy.
                  So, your proposed change is: watts are a 3x’s increase; volts are a 4x’s increase.
                  You should be reducing overall amp load running through cables and gaining cable life by doing so.
                  Another handy tidbit:

                  A little knowledge is worth it’s weight in gold but ya can’t buy a cup of coffee with either, without a fiat money exchange first.
                  Value-No Value- Value
                  The middle step is parasitic energy consumption robbing the system of efficiency, unauthorized by founding engineers, and known as national debt. The congressional service cable attached to the people battery bank and carrying the parasitic draw is huge and a dead-short will destroy the batteries before the service cable is over-heated. To preserve the life of the system, the batteries must have proper in-line fuses in operation.

                  Reply  •  March 30, 2014 at 11:36 am
  • John
    now I‘ll connect my friend hydraulics

    Reply  •  February 29, 2012 at 9:05 pm
    • Eugene
      I have a 48v inverter solar system with 8 102ah 12v deep cycle batteries connected 4 in series and both strings parallel. I bought 8 200ah 12v agm batteries. What is the best to connect such 16 batteries with max capacity.

      Reply  •  Rated article 3  •  May 23, 2016 at 6:23 am
      • BatteryStuff Tech
        In is not recommend to mix and match batteries of different age, capacity, or type. In a situation like yours I would suggest creating two different battery packs, and switching between the packs as needed. We do not sell switches for this purpose, but there are many on the market.

        Reply  •  Rated article 5  •  May 26, 2016 at 10:01 am
        • Katsiana
          Hi, I am a girl and have 2 batteries same capacity and type I need them to power my computer all day without electricity. I was told (by 2 guys i met in the store) to link them in series and they would keep charging each other indefinitely. The exact instructions I was given is connect the battery charger to battery 1, connect battery 1 to battery 2, connect battery 2 to the inverter, plug in the computer and the battery charger to the inverter. I must have done something wrong because both batteries did not charge each other while powering the computer, and battery charger through the inverter. Instead, both batteries ran down and I had to buy two new batteries. These guys told me it would work. What did I do wrong?

          Can you help give me the answers?

          Thanks alot!

          Reply  •  Rated article 5  •  June 27, 2016 at 7:40 pm
          • BatteryStuff Tech
            A charger will draw more energy than it can put out. You are basically running your batteries down, as the charger will be pulling more energy through the inverter than it can put back into the batteries.

            Reply  •  January 19, 2017 at 9:02 am
    • LBP
      On our boat I have 6-agm 6v@ 220ah battery‘s in series to produce 12v. I charge with 3 solar panels and a 100 amp Balmar alternator.We use about 100-125 ah per day. The battery‘s are seven years old and Iam thinking about replacing them. Iam I better off with the status quo or changing the configuration some how ie 12v or 6v parallel/series? Thanks great info.

      Reply  •  February 20, 2013 at 9:15 am
      • BatteryStuff Tech
        If your total voltage is 12 volts, and total capacity is 660 AH, then there is no difference in performance should you choose to use 6v or 12v batteries.

        Reply  •  February 20, 2013 at 9:40 am
        • Guy
          I would like to make 4 battery banks in series using 12v 120ah batteries. Then I would like to connect them in parallel to create an output of 48v 1200ah. I am using all the same kind of battery as a base, but there are 10 of them meaning I would create 2 banks with 3 in a series, and 2 banks with 2 in a series in order to combine for the desired total out put.

          You mention in the article to avoid mixing types of batteries. Would this arrangement I have described work because at the base level I have used batteries that have all the same capabilities? Or will it not work because I have changed the amperage of those batteries by connecting them into series with uneven numbers of batteries in each (those series of 3 being 360ah each, and those series of two being 240ah each)?

          Reply  •  Rated article 5  •  May 19, 2016 at 2:54 pm
          • BatteryStuff Tech
            I’m having a little bit of trouble following how you are setting things up, but I can tell you that even with matching batteries at the base, the bank in a whole needs to be balanced. If you intend to charge them as one bank at one point then I would not suggest using them in different banks, as overtime they will become unbalanced of each other. That is a big issues as some batteries will be weaker, and others will still be good. As it takes longer for the weaker batteries to charge the other batteries will start to get overcharged. This is the point when you can start to bring a whole pack down, with even one battery in a bank starting to get overcharged, and in the end damaged from overcharging.

            Reply  •  Rated article 5  •  May 26, 2016 at 7:14 am

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