How to Test a Car Battery (and Why You Should Do It)
While your car’s battery is essential to its operation, it’s also easy to forget about it, or at least take it for granted when everything is running smoothly. The situation, of course, changes when your battery begins to show signs of weakness or stops working altogether. But there’s no reason to be caught off guard by a dead battery if you can check it yourself. If you’ve never tested a car battery, it may seem like a daunting task, but as Garrett Tortelli, senior category manager at Batteries Plus, explains below, it’s a relatively simple but important process. Here’s what you need to know.
Why You Should Check Your Car Battery
“Let’s start with the obvious: Checking your car’s battery regularly will help you avoid a situation where your battery dies and you’re stranded at home, work, or anywhere else,” Tortelli says. Although there are signs that a car battery has failed (such as taking a long time to start), this is not always the case.
Since you can’t count on your car to tell you when its battery is close to dying, it’s important to have it checked. “While a person can easily test some things on a car themselves, home testing only goes so far,” Tortelli tells me. “Some tests, such as simulated engine starting, known as “stress testing,” must be carried out by a professional using the proper tools and safety precautions.”
How to check your car battery
The easiest way to test your car battery at home is to use a voltmeter or multimeter. As the name suggests, a voltmeter measures the voltage of a car battery. The multimeter also measures voltage, as well as resistance, continuity and other parameters. The testing process that Tortelli recommends only measures battery voltage, so a voltmeter is sufficient. Both tools are affordable and available at most hardware and auto parts stores, as well as online—like this AstroAI Multimeter ($12.99) or this KAIWEETS Multimeter ($15.99).
Here’s how Tortelli suggests checking your car’s battery yourself:
Battery charge level (SoC)
When the car does not start, connect the red lead of a 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 between 12.4 and 12.8 volts,” explains Tortelli. “If the voltage is below 12V, there may be a charging problem or a faulty battery cell.”
Start the engine
Next, Tortelli recommends starting the car. Does it turn over slowly in normal weather? “When it’s cold, a car will often turn over more slowly because everything, [including] the oil, is sluggish,” he explains. “This is fine. However, if it is difficult to turn over [and] slower than usual, this may be a sign that the battery is no longer meeting the vehicle’s CCA specifications – or cold cranking boosters – and is another sign that the battery may be starting to fail.”
Check battery voltage (with vehicle running)
Using a voltmeter or multimeter, check the battery voltage again – this time with the car running. “This will check that the alternator is delivering the correct charging voltage while driving, keeping the battery charged,” Tortelli explains. “The desired voltage should be around 14V—typically 13.8 to 14.5V.”
When should you have your car battery professionally checked?
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 the cold weather sets in, especially for batteries older than three years or batteries that are nearing the end of their warranty. Additionally, Tortelli suggests professional battery testing “if you are experiencing slower than normal starting” or have other concerns about battery life.
According to Tortelli, professional equipment will not only test the battery voltage, car alternator and starter function, but also test the CCA. “The most important test for whether a battery is healthy is whether it meets the requirements of the vehicle’s engine,” he explains. “Simulating the load or discharge of a battery over a period of time can tell you whether the battery is in good condition, in bad condition or on the edge.”