BATTERY PACK FOR POWER TOOL

摘要

PROBLEM TO BE SOLVED: To provide a battery pack for power tool which does not overcharge a secondary battery even if the charge control by a charger is disabled. SOLUTION: This battery pack is equipped with a second power terminal 5c which is connected to the positive electrode of a battery pack 4 and where a charge current supplied from the charger 2 flows, a protective element 6 which opens and closes the path of a charge current to be supplied to the battery pack 4 through the second power terminal 5c, a third control terminal 9 which detects the voltages V1-V4 across secondary batteries 4A-4D individually and operates the protective element 6 thereby opening a charge current path when the detected voltage exceeds a third specified value Vth3. Since the third control circuit 9 operates the protective element 6 thereby opening the charge current path when the voltage V1-V4 across any secondary battery 4A-4D exceeds the third specified value Vth3, it can prevent the secondary battery 4A-4D from being overcharged even if the charge control by the charger 2 is disabled. COPYRIGHT: (C)2007,JPO&INPIT