Patent ID: 8813866

Claim:
A hand-held electric power tool configured to be powered by at least a first battery pack and a second battery pack connected in series, wherein each battery pack comprises a microprocessor and memory, the electric power tool comprising: a tool housing configured to detachably latch the first and second battery packs; a circuit disposed within the tool housing that electrically connects power terminals of the first and second battery packs in series; a controller disposed within the tool housing and comprising a tool microprocessor configured to receive signals respectively outputted from the microprocessors of the first and second battery packs, wherein the microprocessor of the first battery pack outputs a first signal at a first voltage level and the microprocessor of the second battery pack outputs a second signal at a second voltage level different from the first voltage level; a first level-shifter disposed within the tool housing and electrically connected between the controller and the microprocessor of the first battery pack, the first level-shifter being configured to shift the first voltage level of the first signal to the second voltage level that is usable by the tool microprocessor, a second level-shifter disposed within the tool housing and electrically connected between the controller and the microprocessor of the first battery pack, the second level-shifter being configured to shift the second voltage level of a signal outputted from the tool microprocessor to the first voltage level that is usable by the microprocessor of the first battery pack, and a circuit disposed within the tool housing that electrically communicates the second signal at the second voltage level from the microprocessor of the second battery pack to the tool microprocessor.