Title: Rechargeable battery pack for a power tool
Application Number: 200610148557 Application Date: 2006.11.16
Publication Number: 1967964 Publication Date: 2007.05.23
Approval Pub. Date: Granted Pub. Date:
International Classifi-cation: H02J7/00;G01R31/36;B25F5/00
Applicant(s) Name: Matsushita Electric Works Ltd. Address:
Inventor(s) Name: Sainomoto Yoshinori;Ohashi Toshiharu;Miyazaki Hiro
Attorney & Agent: shixia
Abstract:
    A battery pack for a power tool of self-contained over-charge protection is proposed. The battery pack includes a battery stack composed of a plurality of series connected secondary cells, and a charge terminal connected through a charge current path to the battery stack for flowing a charge current from a charger. The battery pack includes an interrupter inserted in the charge current path, and an over-charge detector which detects a cell voltage across each of the secondary cells and actuates the interrupter to open the charge current path when any one of the cell voltages becomes higher than a predetermined threshold (V TH3). Thus, even if the charger fails to limit the charge current, the battery pack can itself protect the secondary cells from being over-charged.
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