US Patent No. 9,472,979

POWER TOOL HAVING MULTIPLE BATTERY PACKS


Patent No. 9,472,979
Issue Date October 18, 2016
Title Power Tool Having Multiple Battery Packs
Inventorship Matthew J. Mergener, Germantown, WI (US)
Assignee MILWAUKEE ELECTRIC TOOL CORPORATION, Brookfield, WI (US)

Claim of US Patent No. 9,472,979

1. A method of operating a power tool with a first battery and a second battery connected in parallel, a first switch being
connected in series with the first battery and the power tool, a second switch being connected in series with the second battery
and the power tool, the method comprising:
with a controller, monitoring a first voltage of the first battery and a second voltage of the second battery;
when the first voltage of the first battery and the second voltage of the second battery are within a predetermined range,
closing the first switch to connect the first battery to the power tool and closing the second switch to connect the second
battery to the power tool;

when the first voltage of the first battery is outside of the predetermined range of the second voltage of the second battery
and the second voltage of the second battery is greater than the first voltage of the first battery, opening the first switch
to disconnect the first battery from the power tool; and

when the second voltage of the second battery is outside of the predetermined range of the first voltage of the first battery
and the first voltage of the first battery is greater than the second voltage of the second battery, opening the second switch
to disconnect the second battery from the power tool.