| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and device for preventing overdischarge of a battery pack having a battery group surely preventing inversion of polarity of each battery in a discharge process. SOLUTION: In order to surely obstruct overdischarge of the battery pack caused by inversion of polarity of one battery having the most dropped capacity and prevent the overdischarge of the battery pack, a continuously repeated differential measurement step 8 detecting an event suggesting possibility of inversion of polarity of a cell is conducted, and in this step, the change with the passage of time of voltage differential between cell groups is checked whether it exceeds differential threshold value or not, and instant inversion of polarity is surely separated from a slow change of voltage differential between both battery groups on a regular characteristic curve. The battery pack including a control circuit 5' executing this method and a battery driven hand held tool device 7 are installed. COPYRIGHT: (C)2007,JPO&INPIT
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