Cheap device that quickly verifies the correct charging of a battery. Very praique for rechargeable batteries but also to find a set of batteries that or those which are no longer good. this avoids throwing all batteries while some are still usable. The operation is basic, which is convenient. sometimes the same stack has an average load times and a good load depending on its position. Just try 2 times each stack for a correct indication. At that price we ask no more