The voltage size or capacity of most batteries is found printed on the sides or bottom of the battery case. A 1.5-volt battery typically is charged to 1.5 volts when new.
A multimeter can be used to test the current charge of a battery or other electric circuit. Connect the red cord of the multimeter to the "+" end of the battery and the black cord to the "-" end of the battery to display the current voltage. A 1.5-volt battery typically has a charge between 1.0 volts and 1.5 volts, depending on how much it has been used. A battery that has less than 20 percent of its original capacity should be replaced.