Bests & Worsts Reviews from Amazon

One star because it'll tell you the difference between an utterly dead battery and one that isn't. BUT, basically, that's all it does. No matter what battery I placed in the unit, unless the battery was completely dead, it would indicate some degree of "Good" - with the little LCD showing almost full bars. But put that battery into any real device and it wouldn't work. Even testing using a simple flashlight; I put an even dozen AA batteries into my test flashlight. Each of them came up "Good" on the tester, and NONE of them generated more than a feeble yellow light, some nothing at all. I rate this device useless.