Patent ID: 7589500

Claim:
A battery pack configured to supply power to a cordless power tool, the cordless power tool having a motor, the battery pack comprising: a plurality of battery cells operable to supply a battery pack discharge current to the motor of the cordless power tool, each of the battery cells having a battery cell state of charge; a switch operable to be alternately positioned in one of a conducting state and a non-conducting state, the switch further operable to enable the supply of discharge current from the battery pack to the motor when the switch is positioned in the conducting state and operable to interrupt the supply of discharge current from the battery pack to the motor when the switch is positioned in the non-conducting state; a controller electrically connected to the switch and to each of the battery cells via a respective connection to each cell, operable to monitor the respective battery cell state of charge of each of the battery cells, operable to control operation of the battery pack, and operable to control the positioning of the switch, the controller including a microcontroller; and a plurality of electrical paths between the controller and the cell connections, each electrical path being associated with a different one of the cell connections, wherein each electrical path among the plurality of electrical paths is independent of the other electrical paths among the plurality of electrical paths, and wherein no two electrical paths share an electrically conductive component, wherein the controller modifies operation of the battery pack by causing the switch to move from the conducting state to the non-conducting state to interrupt the supply of discharge current from the battery pack to the motor when the monitored respective battery cell state of charge of one of the battery cells reaches a predetermined threshold.