To use a multimeter to test batteries, disconnect the battery. Turn the multimeter's dial to the DC voltage section. Set the top end of the testing range to a value that is higher than the battery's maximum voltage. Connect the test leads. Touch one lead to the positive battery terminal and the other to the negative terminal. Divide the reading by the battery's maximum voltage, and multiply by 100 to get the current charge percentage.
A multimeter can test a battery that is still installed in an appliance or vehicle. For safety, cut off all power, and move the battery terminal connectors away from the terminals before testing.
Most multimeters measure AC voltage, DC voltage and ohms. For most household and vehicle batteries, use the DC range. Find the DV voltage options, which are usually printed onto the DC section of the front dial, and choose the one that is higher than the battery's maximum voltage. Push the test lead connectors firmly into the body of the multimeter to guarantee an accurate reading.
If the battery does not register a charge on the multimeter, double-check that the test range starts at zero. When the multimeter's needle does not move, the battery is dead.