When the battery of iPhone is powered off, there will be errors in health itself, because this data source is a very small chip on the battery of iPhone, which is about one twentieth of the size of the fingernail. This chip monitors current data, current and voltage, and the data is obtained through data. There is an error in the battery health of iPhone itself. In fact, if the usage level reaches 85%, we can replace it, but the actual Apple regulation is lower than 80%, so we don't have to worry about your maintenance.