To test a car battery with a multimeter, set the multimeter to measure DC voltage, and set the dial to 20 volts; with the car off, disconnect the battery cables and attach the multimeter leads to the positive and negative posts on the battery. Wait for the reading.
- Disconnect the battery cables
With the car turned off, follow the manufacturer's guidelines for removing the battery cables. Note which is red for positive and which is black for negative. Always use safety gloves and safety glasses when working on a car battery.
- Set the multimeter for 20 volts
Turn on the multimeter and set to measure DC voltage. For a car battery, this is indicated by the letter V with a solid line on top of a dotted or dashed line above the letter. Set the dial to 20v.
- Attach the leads to the battery
The red lead is positive and is to be attached to the positive post on the battery, usually indicated by a plus sign next to it. The black lead is negative and is attached to the negative post on the battery, sometimes indicated by a negative sign next to it.
- Wait for a reading
After a few seconds, the multimeter will display the voltage measured. The minimum desired reading for a working battery is 9.6 volts.