You think your car battery might be low on juice and you'd like to use your multimeter to see if it is really low. Testing a car battery with a multimeter is easy if you know what settings to use and where to connect the leads. Here are the easy steps in testing your car battery with a multimeter.
Open up your hood and locate your car's battery. Be sure to follow the manufacturer's directions and properly disconnect the cables from the battery.
Turn your multimeter off, then set your multimeter to 50 volt scale. This will reset the meter and give a more accurate reading.
Connect the red lead to the positive battery terminal. Be sure to put the lead on the post of the battery and not just on the cable to get the most accurate voltage reading.
Attach the black multimeter lead to the negative battery terminal. Again, be sure to put the lead directly on the post of the battery for the most accurate reading.
Read your multimeter gauge after 15 seconds. If it has a digital readout and you have a 12 volt battery, it should read at least 9.6 volts running through the multimeter for it to take a charge. If it's less than that, you need a new battery.
Check the temperature if your car battery testing is showing lower than 9.6 volts. At lower temperatures, the minimum voltage under load goes down as well. For instance, at 30 degrees F, the minimum voltage is only 9.1 volts.