The Battery Tester may be used to test the following sizes:
1.5V-----AAA,HP6,MN2400,RO3,AA,HP7,MN1500,UM3C,HP11,MN1400,
UM2,D,HP2,MN1300,UM1 and Cell Button batteries.
9V------ PP3,MN1604,6F22,006P
You can simply test battery voltage to determine whether the capacity of the battery is low or high. It won't directly detect the battery capacity precisely
Don't forget : The aa aaa Battery Tester is activated by the battery being checked .Kepp test times as short as possible to avoid unnecessary battery drain.
If the digits did not show the check that battery is touching both contacts, otherwise the battery is completely dead.