BATTERY PACK SYSTEM

PROBLEM TO BE SOLVED: To provide a battery pack system having an electric apparatus and a battery pack used as a power supply unit of the apparatus, in which the battery pack has improved insulation reliability although the battery pack is equipped with a battery cell group consisting of a plurality of battery cells connected in series. SOLUTION: The battery pack 100 includes the battery cell group, and a discharging output terminal 110 for supplying the output of the batteries to an electric apparatus 200. The electric apparatus includes a load section 202, a switch 204 to be operated to be turned on and off respectively by an operator, and a switch detecting section 205 for detecting the on-off of the switch. The system further includes a plurality of energization interrupting elements 130 provided between the battery cells, and a control means for controlling the plurality of energization interrupting elements so that when the switch is on, all the energization interrupting elements are in an energization state to achieve the serial connection of the battery cells, and when the switch is off, all the energization interrupting elements are in an interruption state not to achieve the serial connection of the battery cells. COPYRIGHT: (C)2010,JPO&INPIT