Car battery dealer INTERSTATE statistics, in the so-called bad battery returned, 50% of the battery is actually good, these batteries need to be charged, not replaced. This part of a good battery, just because of the wrong judgment, meaningless to and from manufacturers and distributors, resulting in each other's consumption. On the other hand, due to the lack of efficient testing tools at many car service outlets, it is impossible to find the weakened battery in time before the owner encounters problems, thus losing the potential opportunity to sell the battery. In addition, the traditional methods such as proportion indication, terminal voltage, etc., reflect the state of charge (SOC) of the battery instead of the state of health (SOJ). In many cases, it can not be used as an effective method to check whether the battery needs to be replaced.