This is supposed to test your batteries for good/replace-Recharge.On the good side - it is small, and does SOMETHING.On the not-so-good side1. WHAT does it measure? this is not clear. There is no manual, and thescale is unlabeled. I am *assuming* it measures voltage, but I have noclue if this is under some sort of load or not, and so the results arenot very convincing2. If it DOES mesure Voltage, this is not so good for RechargeableBatteries, as they only give out 1.2V even when fully charged.2. The scale has strange proportions, with more than 2/3rd of it for "bad"and only about 20% for "Good". This is not very useful.