Test the charge of most smaller batteries including button cells & even power tool batteries! This handy mini-tester checks whether your batteries or rechargeable batteries are still ready for use or have to be replaced or recharged. The test is carried out under load -> this results in a more realistic measurements. Analog display with 3 areas: " Replace / Weak / In order" For button cells / AAA / AA / Baby C / Mono D / 9V block Passive operation, therefore no power supply necessary