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
Sometimes 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:
- 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.
- Hold the prongs of your voltmeter to the correct terminals on the battery.
- 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.
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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How to Tell if Your Battery Is Bad in 3 Easy Steps
