How to test a car battery with a digital multimeter

dead battery image by Katrina Miller from

A car that won't start is a source of panic for most drivers, but feeling helpless is optional. Diagnosis of the problem begins with a basic battery test that is within reach of all vehicle owners and can be safely done at home.

An inexpensive digital multimeter can identify or eliminate the battery as the cause of your inoperative vehicle. Before making that call to the auto shop and inviting expensive bills, use a digital multimeter test to test your vehicle's battery.

classic impala headlights image by Jorge Moro from

Turn the headlights on for three minutes to remove residual charge. Switch off the headlights before proceeding. It is not necessary to disconnect the battery after removing the residual surface charge.

Clean the battery terminals with a rag soaked in a solution of 1 tbsp baking soda and 2 cups water. If the positive terminal is covered by a protective plastic cover, lift the cover before cleaning.

Remove residual dirt or visible spills on the battery casing, using the solution and rag.

The Readout image by Cinneman from

Select the DC voltage scale on the digital multimeter, and set the range to 20 V.

Insert the positive (red) test lead of your multimeter into the terminal marked with V (voltage), and the negative (black) test lead into the terminal marked COM (common).

Turn on your multimeter, and clip the free end of the red test lead to the positive terminal of your battery, and the black test lead to the negative terminal. If the test leads end in probes and not clips, hold the tip of the probe against the battery terminal and maintain contact while taking the measurement. The voltage will appear on the multimeter screen.