PURPOSE: To enhance the reliability of the title apparatus by a method wherein a charging operation is stopped when a contact defect is caused due to the deformation or the like of a switch which changes over the charging operation and a load drive.

CONSTITUTION: A switch SW1 is constituted of contacts S1, S2 connected to the side of magnetic poles of a first current detection resistance R1 and a second current detection resistance R2, of a contact S3 connected to a grounding line, of a contact S4 connected to the negative pole of a load M and of a movable contact which is composed of a three-piece fork switch. When the switch is turned on, the contacts S4, S3, 52 are connected, and, when it is turned off, the contacts S1, S3 are connected. Consequently, when the switch is turned off, only the first current detection resistance R1 is connected across an emitter for a transistor Q1 and a ground. On the other hand, when the switch is turned on, only the second current detection resistance R2 whose resistance value is larger is connected. In addition, when the switch fork is deformed and does not come into contact with the contact S1, the supply of an electric current to a storage battery B is stopped.