Testing Batteries

Headlight Test In the dark, pull your car up to a building wall or a garage door. Turn off the engine and leave on the headlights. If they're bright, then your battery is probably fine. If the lights are dim, but get brighter when the engine is started, this tells you the battery could be bad and requires further testing. If the lights are dim and stay dim when the engine is started, this tells you that your charging system requires further testing.

Open Circuit Voltage (OCV) Test An OCV test may be performed with a voltmeter.

We do not recommend that you substitute the OCV test for a specific gravity test, which is more accurate. The OCV test, however, is the only way to determine the state of charge of a sealed no-maintenance battery.

Specific Gravity Test This test is performed with a hydrometer, which is the most accurate hand held tool for determining the state of charge of a lead acid battery.

Load Test This test is a 15-second discharge of the battery at a 1/2 cold cranking amp level. A more accurate testing method than a voltmeter or a hydrometer, the load test is often required to determine whether a battery is good or bad. It is used by professional technicians.