To short-circuit both electrodes of a battery by a conductive member to prevent leakage to the outside when water enters of a battery case by surrounding plural high voltage power supplies formed by plural batteries with the conductive member.

To drive a motor of an electric vehicle, plural batteries are connected in series to form a battery block of sealed structure, and plural blocks are connected in series to from a set battery 10 for obtaining high voltage of 200-300 V. The set battery is stored in a resin-made waterproof insulating box 12, and power is supplied to the outside by an output line 14. Further, the insulating box 12 is surrounded with a net-like conductive net 16 made of copper. When water enters the insulating box 12 by some cause, both electrodes of the battery are short-circuited through the conductive net 16. Thus, at the time of submersion or the like, the current can be prevented from leaking out in a simple constitution. The conductive net 16 is put in a floating state by a frame or the like, where by the conductive net 16 is also functioned as a shield.