How to Tell if Your Battery Is Bad in 3 Easy Steps

Having battery troubles? Yeah, we hear you. Almost everyday, we receive calls and comments about batteries that "won't hold a charge" any more. Maybe you've been in that boat before. To clear up a misconception: a battery isn't like a water bottle. You can't use up half now, and then wait and use half later. It's not a tank of electricity. Also, batteries don't "leak" power like water can. What we're dealing with is a lead acid battery in a plastic box that encases a delicate balance of chemicals which are ready to interact with each other to produce electricity when the load is applied.

If your battery is having trouble holding under load, then chances are it's a chemical issue.

How to test a battery:

Here are some ways to test your battery at home, and determine if it's bad:

1) Inspect the Battery

Bad Battery Bent TerminalSometimes you can tell if your battery is bad by simply taking a good look. There are a few things to inspect:

  • Broken terminal
  • Bulge or bump in the case
  • Crack or rupture of the plastic
  • Excessive leaking
  • Discoloration

Broken or loose terminals are dangerous and can cause a short circuit. If a short did occur, there would be some indication of burning or melting. When a battery short circuits, all the power is unloaded in an instant. That produces a lot of heat, and sometimes even causes the battery to explode.

If the battery is still intact, but there is a bulge in the case, this is usually a result of being overcharged. Other signs such as physical openings in the case are often caused by mishandling. Cracks, splits, and holes will not cause a battery to stop working, but for safety reasons the battery should be labeled unsafe to use.

With wet-cell (flooded) batteries, water levels must be maintained. If they are low, usually refilling them with distilled water will help. But, if the cells within the battery have been exposed to air for a long time, it can cause a problem. When the plates within each cell are exposed to oxygen it can rapidly dry the paste that surrounds the lead plates. When the paste has dried it creates a barrier that prevents the chemical reaction within the battery. This can also cause the sulfation that has already occurred to harden leading to a sulfated battery which is the number one cause of early battery failure. We strongly recommend checking the water levels prior to charging a wet cell battery since charging a dry battery will burn it up. If your battery has plenty of fluid in the cells, but the color is dark, or brownish, this is also an indication of a bad battery. Even if one cell is brown, it is rendered useless and therefore the entire battery is, too. Time to replace your battery!

2) Take a Voltage Reading

The voltage of a battery is a good way to determine the state of charge. Here's a handy table with the breakdown:

State of Charge Voltage
100% 12.7 - 13.2
75% 12.4
50% 12.1
25% 11.7
Discharged 0 - 11.6

If your battery is:

  • Reading 0 volts, chances are the battery experienced a short circuit
  • Cannot reach higher than 10.5 volts when being charged, then the battery has a dead cell
  • Fully charged (according to the battery charger) but the voltage is 12.4 or less, the battery is sulfated

Sulfation is the natural byproduct when the battery discharges. Naturally, re-charging the battery will reverse the sulfation crystals and turn it back into electrolyte, ready to produce power again. But if a battery sat, uncharged, severely discharged, and/or drained for extended periods of time, the sulfation will increase in size and harden onto the plates. This covers the surface area of the plates, removing the chemicals needed to produce power.

Sulfation decreases the potential to reach a full charge, and it self-discharges the battery quicker than normal. Charging a sulfated battery is like trying to wash your hands while wearing gloves. At this point, charging alone will not restore the battery to a healthy condition. The majority of replacement battery purchases occur when the original battery has reached this point.

3) Load Test the Battery

Your local automotive shop is more than able to load test your battery, but it's quite easy to do at home and all you need is a digital voltmeter. For any load test to be accurate, the battery must be fully charged and left to sit 12 hours before load testing the battery. A recently charged battery will hold a residual charge from the charger, so letting the battery sit for 12 hours will release that residual charge and give you a more accurate sense on how the battery will perform under normal circumstances. To the test...

Let's use a motorcycle battery for an example:

  1. Remove the seat and expose the battery in your bike so that you have access to the terminals. Do not disconnect the battery because you will attempt to start the bike.
  2. Hold the prongs of your voltmeter to the correct terminals on the battery.
  3. Now push the start button and watch what the voltage drops to. It doesn't matter if the bike starts or not, what you're looking for is a voltage reading.

A healthy 12 volt  battery should maintain a voltage range from 9.6 - 10.5 volts under the load for a good 30 seconds straight.

For starting batteries we don't expect you to run the starter for 30 seconds, so if you see the voltage meter drop within the voltage range and it sounded like a good strong start, then you probably just had a discharged battery. However, if under the starting load the voltage drops below 9.6v, then it is most likely time to replace the battery.

For deep cycle application if the battery holds under load for a few seconds then voltage starts to steadily drop this would indicate a problem with the battery.  If the voltage instantly drops to 0 volts, that is also a problem. We call this the open cell. On a new battery, this can be a result of manufacturing flaws, but it also may be caused by sulfate crystal buildup.

DC Voltage

A common occurrence with open cell batteries is that under the intense heat of the load, one or more of the weld pieces connecting the cells together is coming loose and separating. This will cut the current, and voltage will drop. When the battery cools off, the pieces will touch, barely giving a complete connection. This gives you a false voltage reading. Batteries with open cells may read fully charged in idle, but they fail under a load test every time. Once a battery reaches this point, there is no going back. The best thing to do is recycle the thing.

How to tell if a battery is bad or good: These 3 steps will help you test and determine if your battery is truly bad or getting there. Sometimes it's obvious if there is a failure, but other times it's not. Flooded batteries make it possible to simply look inside the cells and determine if the battery has a physical defect. But for sealed AGM and Gel batteries, it requires testing. The only tools you really need are a battery charger and a digital voltmeter. If your battery experiences any of the symptoms described in the steps above, then maybe it's time to replace the battery.

Look no further. We've got a wide selection of powersports batteries for your motorcycle, ATV, scooter, jet ski, or snowmobile. But we also carry batteries for lawn mowers, wheelchairs / mobility scooters, UPS systems, RVs, and marine applications. Whether you need a starting battery or a deep cycle battery, we have the stuff. And all of our replacement batteries come with warranties to ensure that you won't have any of these problems with your new battery.

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  • Eric L I am looking to test the batteries on my Ryobi 54" zero turn mower; there are 4 total, and they are Leoch Model LDC12-115. I know next to nothing about batteries and am hoping folks can guide me toward a good way to test these and make sure they are not operating at a sub-par level, especially since they are still under warranty. I know that these need to be charged before use and need to be kept plugged into the charger at all times (per Ryobi instructions), but I'd like more intel on how to test them and also whether I should get a small battery blanket since the mower will be kept over the winter in a wood-paneled shed (with power); I am in northern Maryland... it gets cold, but not brutal. Thanks for your time and any and all advice. Eric

    Reply  •  October 6, 2021 at 12:35 pm
    • BatteryStuff Tech If it is safe to access the batteries while the mower is running you could put a volt meter on each battery and see how they are holding under load. The voltmeter would only detect what is between its positive and negative, so the battereis could still be tested like above while the mower is turned on. However, I bet the manufacturer warns against such practices and we don't want anybody getting hurt, so it might be simpler to get a load tester and test the batteries while the mower isn't running. As far as weather is concerned you do not need to be worry about the batteries freezing if they are being maintained with a charger. A fully charged battery will not freeze in your locations since the acid concentration would prevent the battery from freezing, so not heating device would be needed.

      Reply  •  November 2, 2021 at 10:47 am
  • Michael Craggs Hi, hoping you can help. . I bought a 1.5W solar trickle charger for my 12V motorcycle battery, as it lives in a shed away from our house. It's been 3 weeks since my last ride and yesterday the bike wouldn't turn over when I tried turning it on (however the lights and dashboard did all light up). Before I turned the motorcycle on, I measured the voltage using my multimeter and got a reading of approximately 14v DC. After the failed attempt of trying to start up, I turned off all the power to the bike and took another measurement. This time it's reading was approximately 13vDC. I would have thought this voltage would be good enough to turn over the engine, but my bike is still not starting up?

    Reply  •  June 6, 2020 at 3:37 pm
    • BatteryStuff Tech It is possible for the battery to take a charge, but not longer be able to hold under load. I would suggest charging the battery, and once charged disconnect the battery from both bike and charger and let it sit for 12hrs. After 12hrs you can hook it back up and see if the battery is able to start your bike. Typically a good battery will hold under load at least 9.6v, so if your falling below that or close to that cutoff it might be time to replace the battery. If you find the battery is doing just fine you may have a parasitic draw that you need to track down. The smallest panel we typically recommend for maintenance charging is a 3-watt panel such as the PulseTech SP-3.

      Reply  •  June 15, 2020 at 3:37 pm
  • Boris Battery won't hold charge over night, so I disconnected from the vehicle, charged to a full charge, let it stay disconnected overnight and next day after 18 hours the voltmeter indicated 11.7 volts. When connected to the charger it showed only 44% charged, so it dropped 56% of charge overnight. Looks like the battery needs to be replaced?

    Reply  •  May 30, 2020 at 11:09 am
    • BatteryStuff Tech It sounds like your battery is no longer able to maintain is charge, so I would recommend replacing the battery.

      Reply  •  June 15, 2020 at 3:24 pm
  • Dois Sossamon Trolling motor batteries give out after 2 hours but batteries still charge up to 13 v. Could it be motor worn out, it's old.

    Reply  •  May 26, 2020 at 8:51 pm
    • BatteryStuff Tech It is possible for the batteries to still take a charge but no longer be able to hold under load. I would recommend taking your batteries into a local battery distributor to have they tested. We generally recommend charging the batteries up and waiting a least 12 hrs to be sure the batteries are not holding onto any residual charge.

      Reply  •  June 15, 2020 at 3:13 pm
  • Thomas Eichen Thanks this was exactly what was happening to my motorcycle battery.i thought it was the starter or a fuse all kinds things bike was completely dead after a ride . As soon as i went to start it nothing no lights or anything .tested it showed 0 volts removed cables it showed 12.7 volts. Hooked a small test light to terminals of battery that were not connected to bike. it was dim at first then got bright. i watched meter jump from 7 volts to 12 . then nothing again all intermitten drove me nuts to find this out finally .

    Reply  •  April 17, 2020 at 2:16 pm
  • Mark Jilks Info was very helpful. I have a new battery that will die over night after a full charged to 13.7 volts you think it's the battery or short in the truck.

    Reply  •  April 10, 2020 at 9:45 am
    • BatteryStuff Tech While some battery may accept a full charge that doesn't mean the battery will retain that charge. Ideally, the best way to know if your battery is good is to charge it out of the application, and come back 12hrs later to see what the voltage of the battery drop down to. If the battery dropped to 12.4v or lower, it would be considered a weak battery.

      Reply  •  April 10, 2020 at 10:08 am
  • Grey My Optima Blue will charge up and hold at 12.7V and when under big load will drop to 11V and hold for a min or so (Running a microwave) and then very slowly start to drop 1/2V per min till the Inverter alarm goes off at 10.5V Is this considered a good or bad battery?

    Reply  •  February 4, 2020 at 1:58 pm
    • BatteryStuff Tech Powering an a microwave through an inverter requires a battery that can hold under a large amp load. Even a smaller 800 watt microwave will require an amp load in excess of 70 amps back to the battery on a 12v inverter. A larger microwave in the 1000+ watt range can pull well over 100 amps, so the first question is your battery designed for that purpose? I can tell you that the smaller group D34M Optima Blue Top is only a 55AH battery and could only last under load for about 12 mins before you start to excessively discharge the battery. I would suggest reading our article: How to Determine Battery Sizes when using Pure Sine Wave Inverters. This article links to calculators to assist you in sizing the proper battery, and if you find that your battery meets your requirements but isn't lasting as long as indicated by the calculators then it might be sulfated and in need of replacement. Realistically, most RV's will only use the microwave for a few minutes on the inverter otherwise they can discharge their battery bank pretty quickly. Ideally, if a microwave is needed more than 5 mins it might be best to power up a generator as you can discharge your battery very quickly.

      Reply  •  February 14, 2020 at 12:27 pm
  • Paul Very Good Info!!

    Reply  •  July 2, 2019 at 8:26 pm
  • Rich Really great info! Thanks for puttin' it out here Rich

    Reply  •  April 22, 2019 at 11:09 pm
  • Lori Hanger Been working for a parts store for about 17 years. Cant always teach you the things you need to know, while your working. You have to look for the knowleadge of others if you are willing to learn. So you can pass it on to your customers and employees . The reason I read this article is because it was my very own battery giving me problems.
    Thank you. Now I know what to look for and test it or at home.

    Reply  •  December 27, 2016 at 8:21 am
  • Manny thanks for the article, really helpful.

    Just a question about dry cells. How long for an idle battery with a dry cell before it gets damaged? just a rough idea? 6 weeks? 6 months?

    Thanks for sharing your knowledge.

    Reply  •  November 4, 2016 at 2:23 am
    • BatteryStuff Tech span class="caps">AGM and GEL cell batteries have a slower discharge rate than wet cells. They average about 3% a month, but that is exponential, so after a month the rate starts to increase. In general we recommend that if you are not going to use a battery put it on a maintainer. However, if you are not able to I wouldn’t recommend just letting it sit more than a couple of months, or the sulfation that is building up in the battery will start to harden.

      Reply  •  January 16, 2017 at 1:50 pm
  • Rajesh Kumar Quite simple and informative….

    Reply  •  October 21, 2016 at 2:56 pm
  • Gerry I had a battery that got submerged, the poles were covered in water, for a week and the battery drained down to 3 volts. There is no visual damage to the battery. Any chance this battery can be used again?

    Reply  •  October 17, 2016 at 2:25 pm
    • BatteryStuff Tech Unfortunately, the electrolyte most likely mixed with the water and was highly diluted. This is the reason why the voltage dropped so much, and unfortunately you cannot get the acid back. In a situation like this we recommend replacing the battery.

      Reply  •  January 16, 2017 at 12:59 pm
  • Anandaraj When my computer ups in battery mode it will turn off after 4 beep sound what i do?

    Reply  •  October 15, 2016 at 4:23 am
    • BatteryStuff Tech I would consult with the manual of the UPS, but it sounds like it is no longer able to hold under load when using the batteries. If in fact it is time for the batteries to be replaced you can view our replacement UPS Batteries.

      Reply  •  January 16, 2017 at 12:42 pm
  • Angie Hunt Thanks for all the info. It was just the things I was wondering so I could determine what to do next.

    Reply  •  October 13, 2016 at 2:48 am
  • Pete I have a 2009 Yamaha Nytro snowmobile that worked great until I replaced the six year old battery. After running trails, two successive replacement batteries died and would not take a charge. The replacement AGM batteries were identical specs to the original YUASA and each failed after about four hours of riding. The second replacement whistled/hissed, then made a pop like a firecracker when it died.

    Does this sound like bad/shorting batteries or a charging system failure? Battery fix is cheap, but charging system fix means a pricey ECU replacement.

    Reply  •  October 6, 2016 at 5:53 am
    • BatteryStuff Tech With both failures happening about 4hrs into a ride… It sounds like a charging system failure sending too much charge to the batteries. I would have your charging system checked out.

      Reply  •  January 16, 2017 at 1:51 pm
  • Sam Helpful information there!

    A small question for the experts here:
    I have a 150cc motorcycle whose battery charging system consists of a Rectifier-Regulator that partly supplies the power for the headlight(35W) as well as performing the battery charging simultaneously. Hence, my headlight flickers (which is expected from AC supply).
    I wished to connect the headlight directly to the battery supply and use a LED headlight(20W – low/30W -high). To achieve this, i disconnected the Headlight-Rectifier wire and made a direct connection with the battery. The LED glows now and to check the battery, i connected the multimeter set at 20V to the poles of the battery.

    On Load conditions, the battery shows a positive increase in Voltage upto 13.4 – 13.8V with rpm above 3000, I used the motorcycle at night and in the morning i checked the battery at no-load, it was around 12.42V. My battery is okay, isnt it?

    Reply  •  October 2, 2016 at 12:58 am
    • BatteryStuff Tech Your battery is starting ito enter the weak range, so I would replace when you start to notice. Anything less that 12.4 is considered a sulfated battery, so i would recommend charging the battery, and if it settles back to that level I would consider replacing at the first sign of weakness.

      Reply  •  January 16, 2017 at 10:54 am
  • Richard Peter Very useful article! Thank you for sharing!

    Reply  •  September 21, 2016 at 4:01 am
  • Ham My gsr600 battery was over charging so I replaced the rectifier but again it is showing overcharging, is there some thing wrong with the battery? I have already checked all the sockets and earth cable.

    Reply  •  September 19, 2016 at 11:36 pm
    • BatteryStuff Tech It definitely could be a weak battery! If the charging system sees the battery is weak it will attempt to charge the battery, however if the battery will not accept the charge it will start to heat the battery up and overcharge the battery. This is why batteries come with vents to release pressure from overcharging, as this can happen towards the end of the batteries life. I would suggest having your battery tested.

      Reply  •  January 16, 2017 at 10:43 am
  • Scott So I tested my battery and its reading 12.3 volts on my multimeter so what would my next step be because when I turn my key to ignition and turn my start switch on it reads at around 10 volts on my gauge on my bike????

    Reply  •  August 18, 2016 at 5:51 pm
    • BatteryStuff Tech At 12.3 your battery is about at about 62% of capacity, and would be what we consider a weak battery. I would suggest charging, then let it sit off the charger for more than 12 hrs to see if your readings go up. If the readings stay the same I would consider getting the battery replaced.

      Reply  •  January 16, 2017 at 10:11 am
  • Shailendra Tripathi I have 30 SMF battery of 12V/100AH.The floating voltage of all battery is between 13V-13.80V but after testing with load the voltage drop down upto 10.50V.The 10.50v battery is considered weak battery .please reply us.

    Reply  •  July 13, 2016 at 12:46 am
    • BatteryStuff Tech A battery under no load sitting at 10.5 would be considered a bad battery for a 12v battery. However under load you have to interpret you load tester’s result, and most are designed to put a high load on the battery, and in most cases will drop a battery into the 10 volt range.

      Reply  •  January 16, 2017 at 10:02 am
  • Dim Really helpful, thanks. Battery full, but starting gave only ‘tick tick tick’ very quickly. Testing DC under load showed immediate drop to 4-5V….and then the battery came up to 10 V only.

    Reply  •  June 7, 2016 at 5:03 am
  • Chad I have a 98 dodge ram 1500. I sorta put it in a mud hole and now it wont start. I put a new starter on it tonight cuz the old one went bad…. Ive tried jumping the truck but my battery gauge wont go over 11. And the motor wont turn…

    Reply  •  June 3, 2016 at 7:33 pm
  • Tony E I have a minnkota 30amp battery charger in my boat, I notice when I was charging the other day that one of the banks said check battery connection, does this mean the battery is bad, I looked at the battery and everything looked good. Any suggestions?

    Reply  •  May 19, 2016 at 9:52 pm
    • BatteryStuff Tech It could be the charger, or the battery… In my experience it points to the battery if the charger is still alerting you that there is an issue, but every once in awhile it can be the charger as well. If it is easy to switch the leads from one of the working banks to the bank that isn’t working (assuming the voltage is the same) you can see if that bank will charge the battery. If you get the same result it is most likely the battery. However if that bank takes off charging it could be the charger. Before replacing the charger I would suggest going through the troubleshooting steps in the manual, as you may just need to rest the charger.

      Reply  •  May 24, 2016 at 12:09 pm
  • BatteryBhai Thanks for the post. Really helpful post to knowing when battery goes dead.

    Reply  •  May 19, 2016 at 3:25 am
  • Josh Can i ask a question to you wonderful electrics experts. scenario:
    bike draining battery.
    so far i Put new battery on reading 13.3 volts.
    when bike running it showing 14.2 volts (this shows generator/stator and regulator are all working as should, yes?
    now bike turned off, keys removed:
    I have measured the Milliamps (draw on circuit) using the DCA Setting on 20m, with tester in circuit, and i’m getting a reading of 11.24?
    i disconnected every attachment from the harness and the 11.24 is made up of:
    3.00 from dash and 8.24 from the ECU.
    1. should the ECU have power when ignition off?
    2. is either of thoes my problem?
    thanks in advance!

    Reply  •  May 2, 2016 at 2:43 pm
    • BatteryStuff Tech Josh,
      Your ECU definitely should not be drawing power when the bike and ignition are turned off. I am not quite clear on your test results though. You measure for milliamps when testing for draw, but the results you give me (11.24) is a voltage number. Can you please clarify. I don’t believe that will change my diagnosis, but I do like to have complete and accurate info when working an issue.

      Reply  •  May 3, 2016 at 9:27 am
  • Lillian Schaeffer This is some great information, and I appreciate your point that a bulge in the case of a battery means it’s dead. My car wouldn’t start earlier today, so I checked the battery, and there was a weird bulge in the case. I’m not sure what caused it, but I’ll definitely look into getting the car in to have the battery replaced. Thanks for the great post!

    Reply  •  April 14, 2016 at 4:30 pm
  • Mabel Margaret Good post.

    Reply  •  August 7, 2014 at 11:58 pm
  • Mabel Margaret Inspection of battery is essential before replacing Harley starter.

    Reply  •  April 11, 2014 at 3:21 am
  • David Netherland You guys should give lessons to our local Advanced Auto Parts store. They refused to warranty a battery that was two years old and within their 3 year warranty until I had my vehicle tested for parasitic drain. I had to jump it off every other day for two weeks, but before that no issues at all. I finally made them test it WITHOUT me jumping it off first. It had 4.8 volts. They finally replaced it when I got District Management involved. The district manager was even ruder though. I will have to give you guys a try next time. Thanks for the valuable info and not being ashamed to publish it. Sounds like you guys might understand customer service a lot better than they do.

    Reply  •  February 1, 2014 at 9:26 pm
  • Cameron Jolie Nice blog for Automotive.

    Reply  •  November 22, 2013 at 1:26 am
  • J. Craig Hembree Great read Ty for the refresher course.

    Reply  •  October 20, 2013 at 9:20 am
  • Mr Dennis B. Zwolle Hay, thanks for the tip, yup that‘s what I thought brown water indicates loosened rust particles floating around, also can short between plates! My family has this Motor home that had a dynamite battery, marine die-hard they never took care of! Well, it died hard alright, last two cells were dry to the bone! Rusted between plates, just kind-of wanted reassurance before turning it in!

    Reply  •  May 9, 2013 at 1:50 pm
    • Jeremy Fear Yeah, when cells are not equally drained there is indication that one or more cells is defective, causing all the others to be pulled down with it. I would recommend replacing the battery. Thanks

      Reply  •  May 20, 2013 at 7:59 am
  • Pete As HST said – “Give ‘em Hell” – loved your video. Do you folk make batteries for use with solar panels?

    Blessings to you all Pete
    Reply  •  August 13, 2012 at 10:25 am
    • Jeremy Fear We do! You can see all of the batteries that are designed for solar use at

      Reply  •  August 15, 2012 at 11:07 am
  • Gerald Robinson I enjoy your information on batters. Don‘t drop me from your list. Thanks Gerald .

    Reply  •  August 11, 2012 at 4:31 pm
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