To properly and safely check the power in your car battery, be sure to be wearing work gloves and protective eye-wear first.
- The car lights and the engine will need to be off, then you can open the hood to begin testing.
- Take the red voltmeter cable, place it on the plus, or positive, side of the car battery.
- Take the black voltmeter cable, place on the minus, or negative, side of the car battery.
- The reading on the voltmeter will be at 12.4 or better if the battery has plenty of cranking power left.
- If the reading on the voltmeter shows 12.2 or worse, the battery has lost the ability to hold the charge or crank over the car engine and should be replaced.