PURPOSE: To permit the confirmation of connection of a battery by a method wherein the title circuit is provided with a detecting means, detecting that the secondary voltage of a transformer is lower than a predetermined voltage, and an indicating means, in the charging circuit charging through the transformer.

CONSTITUTION: When a storage battery B is not connected to a charging circuit, a transistor Q1 is put ON whereby the transistor Q2 is put OFF and a light emission diode D4 is being extinguished. When the storage battery D is connected to the charging circuit, the transistor Q1 is not put ON whereby the transistor Q2 is put ON and the light emission diode D4 is lighted. When a plug 3 is pulled out of a commercial AC power source while connecting the storage battery D as it is, current is not conducted from the battery DB to a detecting and indicating circuit 1 whereby the transistor Q2 is not put ON and the light emitting diode D4 is not lighted. According to this method, it may be confirmed whether the storage battery B is connected to the charging circuit or not.