Not feeling that spark? Here’s how to test a car battery

How to test a car battery
Joseph Belanger/123RF

When it comes to car problems, nothing is ever convenient. It seems like your vehicle plots the perfect moment to give you grief, and the majority of the time, it involves a dead battery. While it’s true the starter motor, alternator, or spark plugs could be behind your vehicle’s refusal to start, it’s most likely that your battery is zapped. In this article, we’ll cover how to test a car battery, specifically its voltage, and also break down what each reading means.

Testing

Diagnosing a car battery is a breeze, but you will need a piece of equipment called a multimeter. These can be picked up for cheap either at your local auto parts store or online, and will quickly tell you whether or not your battery is out of juice. Though you can find analog multimeters, we’d recommend investing in a digital unit so there’s no misinterpreting the readout.

Finding your vehicle’s battery should be a cinch, but some automakers put them in odd places such as the trunk or under the rear seats. The vast majority can be found under the hood however, to the right or left of the engine. You can identify the battery by the positive (red/plus sign) and negative (black/minus sign) terminals that either route to a rectangular housing box or directly to the exposed battery.

Once you’ve located the unit, make sure your vehicle is turned off. If you’re using a digital multimeter, set the dial to DC voltage. Next, take your multimeter’s black lead to the negative battery terminal and the red lead to the positive terminal.

At this point, your multimeter will give a voltage readout. Here are some guidelines, courtesy of yourmechanic.com:

12.66+ volts 100% charged
12.45 volts 75% charged
12.24 volts 50% charged
12.06 volts 25% charged
11.89 volts 0% charged

If you’re seeing 12.45 volts or higher, your battery is in good shape and it’s time to check other common culprits. If you’re below a 75% charge, your battery might still bring the car to life, but not reliably. Below this threshold, your battery may need recharging or even replacing.

Final thoughts

If you struggle with any part of this process, take a trip to your local auto parts store and ask for help. Most shops are happy to help test, remove, recharge, and replace your car’s battery. You get a free hand, and they will (hopefully) earn your business in the future.