How to Test Your Car Battery (and Why You Should)

Although your vehicle's battery is essential to its operation, it's also easy to forget about—or at least take for granted—when everything is running smoothly. That, of course, changes when your battery starts showing signs of weakness, or stops working altogether. But there's no reason to be caught off guard by a dying battery when you can test it yourself. If you've never tested a car's battery, it may sound like a daunting task, but as Garrett Tortelli, a senior category manager at Batteries Plus, explains below, it's a relatively simple—but important—process. Here's what to know.

Why you should test your car's battery

Let's start with the obvious: Regularly testing your car's battery will help you avoid a situation where your battery dies and you're stranded at home, work, or anywhere else, says Tortelli. While there are signs that a car battery is on the fritz—like taking a long time to start—that's not always the case.

Because you can't rely on your car to let you know that its battery is close to being drained, it's important to have it tested. "While an individual can easily test certain things on the car themselves, at-home testing only goes so far," Tortelli tells me. "Some testing, like simulating an engine starting—known as a 'load test'—should be checked by a professional with the right tools and safety precautions."

How to test your car's battery

The easiest way to test your car's battery at home is to use either a voltmeter or multimeter. As its name suggests, a voltmeter measures the voltage of a car battery. A multimeter also measures voltage, as well as resistance, continuity, and other things. The testing process that Tortelli recommends only measures the battery's voltage, so a voltmeter is sufficient. Both tools are affordable, and available at most hardware and auto parts stores, or online—like this AstroAI Multimeter ($12.99) or this KAIWEETS Multimeter ($15.99).

Here's how Tortelli suggests checking your car's battery on your own:

Battery state of charge (SoC)

When the vehicle isn't running, connect the red lead of the voltmeter or multimeter to the positive terminal of the battery, and the black lead to the negative terminal of the battery. "[The] voltage should be around 12.4 to 12.8V," Tortelli explains. "If the voltage is below 12V, you could have a charging issue, or a defective cell in the battery."

Start the engine

Next, Tortelli recommends starting the vehicle. Does it turn over slowly during normal weather? "It’s common in the cold for the vehicle to turn over slower, as everything [including] the oil is sluggish," he explains. "This is normal. However, if it struggles to turn over, [and is] slower than usual, this could be a sign the battery is no longer hitting the vehicle’s CCA—or cold cranking amps—specs, and is another sign the battery may begin to fail."

Check the battery voltage (while the vehicle is running)

Use a voltmeter or multimeter to test the battery's voltage again—this time with the vehicle running. "This will check that the alternator is putting out the right charging voltage while you're driving, keeping the battery charged," Tortelli explains. "The desired voltage reading should be around 14V—typically between 13.8V and 14.5V."

When to have your car's battery tested professionally

As Tortelli mentioned above, in addition to checking your car's battery yourself, you should also have it professionally tested. He recommends bringing your vehicle in for professional battery testing every fall, before cold weather arrives—especially for batteries more than three years old, or those getting close to their warranty expiration period. Other than that, Tortelli suggests professional battery testing "if you're experiencing the slower than usual starting power on the engine," or have other concerns about your battery's lifespan.

According to Tortelli, the professional equipment will not only test the battery voltage, car alternator, and starter functionality, but it will also test for CCA. "The most important test on whether or not the battery is good is to hit the rating of the car's engine needs," he explains. "Simulating a load, or draw of the battery, for a period of time can tell you if the battery is good, bad, or on the edge."