| 摘要 |
PROBLEM TO BE SOLVED: To effectively avoid the overdischarge of a lithium ion secondary battery to use the battery conveniently. SOLUTION: A lithium ion secondary battery 1, a motor 2 and a protective circuit 4 are built in an electric apparatus. The protective circuit 4 has a 1st protective circuit 4a and a 2nd protective circuit 4b. If a 1st voltage detection circuit 5a detects the battery voltage and the detected battery voltage is lower than a 1st set voltage, the 1st protective circuit 4a turns off a 1st switching device 6a to cut off the current of the motor 2. If a 2nd voltage detection circuit 5b detects the battery voltage and the detected battery voltage is lower than a 2nd set voltage, the 2nd protective circuit 4b turns off a 2nd switching device 6b to cut off a current supplied from the lithium ion secondary battery 1. The 1st set voltage is higher than the 2nd set voltage. The 1st protective circuit 4a cuts off the current of the motor 2 and, if the battery voltage is lowered further, the 2nd protective circuit 4b cuts off the current of the lithium ion secondary battery.
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