How Can You Tell if There is a Problem With a Car Battery With Just a Voltmeter?

Tips & Support
OPTIMA Batteries
Milwaukee, WI

A voltmeter has many functions, but when it comes to problems with your car battery, do you know how to use a volt meter to identify potential issues? Voltmeters can be intimidating for some folks to use, so we'll try to keep this as simple as we can. Voltmeters can measure the voltage of a car battery, which can give you a good indication of how much energy is in the battery- kind of like a gas gauge on a car.

Fully-charged, most car batteries will measure at least 12.6 volts and measuring voltage will give you a good idea of where your battery is at in that regard, as illustrated in this chart below:
battery voltage chart
As you can see from this chart, a fully-charged 12-volt battery will measure well above 12.0 volts. In fact, a battery that measures 12.0 volts is actually quite discharged ("SLI" stands for Starting/Lighting/Ignition batteries, while "DC" stands for Deep-Cycle batteries). 

While voltmeter settings can vary, if you set your voltmeter to measure volts (sometimes "V"), and place the positive (red) lead on the (+) terminal and the negative (black) lead on the (-) terminal, it should show you battery voltage. If your battery voltage measures somewhere in between 10.5 and 11.0 volts, the battery is definitely discharged and could have a bad cell. Anything below 10.5 volts will indicate the battery is severely-discharged, perhaps beyond the ability of most battery chargers to recover it (OPTIMA chargers and maintainers can charge batteries that have been discharged to as low as 1.25 volts).

If your voltmeter indicates your battery is deeply-discharged, you should try to fully-recharge it with a battery charger (not your vehicle's alternator). This could take 12-24 hours or longer, depending on the size of the battery, the depth of discharge and the output of your charger. Once you have attempted to fully-recharge your battery, a local battery professional can load-test it for you, which can provide a more definitive answer as to the health of your battery. You can find a professional near you, by using the "Find Your Store" search function at the top of our website.

Many battery retailers will offer this service free of charge and it should give you a good indication of whether or not you can continue to use your battery or if it needs to be recycled and replaced.