A battery pack of a power tool includes a plurality of cells connected in series, a controller, which is configured to detect a charge current and/or a discharge current of the plurality of cells, estimate remaining capacity of the plurality of cells at least base on an integral of the charge current and/or the discharge current of the plurality of cells over time and generate or select a power supply capability parameter for limiting power of the power tool at least base on the remaining capacity of the plurality of cells, and a memory, which is configured to store data related to the remaining capacity of the plurality of cells.