How to check your car battery health

Three vehicles drive down a mountain, forested road

March 3, 2019. Testing your battery is something you may not associate with regular car maintenance like getting an oil change, but the battery is needed for everything from starting your car to powering your car’s computers and devices. Dead batteries are a common reason for roadside assistance calls and making sure your battery is in good condition could prevent the hassle of your car breaking down unexpectedly. You can check your car battery quickly and easily yourself.

The headlight test

The quickest and easiest test to see if there’s a potential problem is the headlight test.

Simply start the car and turn on the headlights. Do they seem normal? If yes, great.
Now rev the engine. If they stay at the same brightness your electrical system is probably fine. If your headlights dim it means that they’re running off the battery and the alternator is producing only a small charge or none at all. If they get brighter when you rev the engine it means the alternator is producing a charge, but at idle it may not be enough to charge the battery.

How many volts should a car battery have when fully charged?

A car battery with a full charge should have at least 12.6 volts and measure at 13.7-14.7 when the engine is running.

How to use a multimeter to test a car battery

Using a multimeter is one of the easiest ways to test your car battery. You should be able to find one in any hardware store and it’s a good idea to keep one in your car.

Make sure the voltmeter on your multimeter is set to 20 DC volts. The voltmeter section of your multimeter will have a “V,” which is the abbreviation for volt.
Touch the positive (red) meter probe to the positive (red) battery terminal
Touch the negative (black) meter probe to the negative (black) battery terminal
Ask a friend to turn the headlights on. This provides the battery with a light load.
At 26.6 degrees Celsius a reading for a battery with a good charge is about 12.5 volts or higher, 12.3 volts means about a 75% charge, 11.8 volts or lower means 25% or less.
Not driving often enough, or running electronics when the engine is not on, or otherwise depleting the battery.
If your battery is consistently charged at less than 80%, acid stratification can occur. This means that the electrolyte collects at the bottom of the battery, causing the upper half to be acid-poor. Acid stratification reduces the battery’s performance and may cause it to fail.

What causes battery failure

Not driving often enough, or running electronics when the engine is not on, or otherwise depleting the battery.
If your battery is consistently charged at less than 80%, acid stratification can occur. This means that the electrolyte collects at the bottom of the battery, causing the upper half to be acid-poor. Acid stratification reduces the battery’s performance and may cause it to fail.