US Patent 7125268 Power source device

In a power source device including a battery pack, a safety switch is provided between a given pair of battery modules connected to each other. The safety switch connects and disconnects those battery modules by insertion and removal of a safety plug to/form a switch body. The power source device also includes an insertion prevention unit, such as a lock, for preventing the insertion of the safety plug to the switch body in such a manner that prevention of the insertion of the safety plug is releasable. A release operation unit is kept by a worker who removes the safety plug, so that safety of the worker against electric shock is ensured.