A battery pack configured to couple to a power tool by sliding in a sliding direction relative to the power tool, comprising: a plurality of battery cells disposed in a housing (32, 34); plus and minus power terminals (312a, 312b, 314a, 314b) electrically connected to the plurality of battery cells and adapted to be electrically connected to corresponding plus and minus power terminals (212, 214) of the power tool, at least one first signal terminal adapted to transmit a signal from the battery pack and adapted to be electrically connected with at least one corresponding signal terminal of the power tool, and at least one second signal terminal (311, 315) dedicated for connecting only to at least one corresponding second signal terminal (511, 515) of a charger, wherein: the battery pack is further configured such that, when the battery pack is coupled to the charger by sliding in the sliding direction relative to the charger, the plus and minus power terminals (312a, 312b, 314a, 314b) respectively electrically connect to a pair of power terminals (512, 514) of the charger, and the at least one first signal terminal and the at least one second signal terminal (311, 315) respectively electrically connect to corresponding signal terminals (511, 513; 515) of the charger; and wherein the plus and minus power terminals (312a, 312b, 314a, 314b) and the at least one first signal terminal are disposed adjacently and in parallel in a direction that intersects the sliding direction, or the plus and minus power terminals (312a, 312b, 314a, 314b) and the at least one first signal terminal are respectively spaced apart by a predetermined spacing in a direction that intersects the sliding direction, characterized in that the at least one second signal terminal (311, 315) is disposed on an outer side, in the direction that the terminals are disposed in parallel, of the plus and minus power terminals (312a, 312b, 314a, 314b) and the at least one first signal terminal. a plurality of battery cells disposed in a housing (32, 34); plus and minus power terminals (312a, 312b, 314a, 314b) electrically connected to the plurality of battery cells and adapted to be electrically connected to corresponding plus and minus power terminals (212, 214) of the power tool, at least one first signal terminal adapted to transmit a signal from the battery pack and adapted to be electrically connected with at least one corresponding signal terminal of the power tool, and at least one second signal terminal (311, 315) dedicated for connecting only to at least one corresponding second signal terminal (511, 515) of a charger, wherein: the battery pack is further configured such that, when the battery pack is coupled to the charger by sliding in the sliding direction relative to the charger, the plus and minus power terminals (312a, 312b, 314a, 314b) respectively electrically connect to a pair of power terminals (512, 514) of the charger, and the at least one first signal terminal and the at least one second signal terminal (311, 315) respectively electrically connect to corresponding signal terminals (511, 513; 515) of the charger; and wherein the plus and minus power terminals (312a, 312b, 314a, 314b) and the at least one first signal terminal are disposed adjacently and in parallel in a direction that intersects the sliding direction, or the plus and minus power terminals (312a, 312b, 314a, 314b) and the at least one first signal terminal are respectively spaced apart by a predetermined spacing in a direction that intersects the sliding direction, the battery pack is further configured such that, when the battery pack is coupled to the charger by sliding in the sliding direction relative to the charger, the plus and minus power terminals (312a, 312b, 314a, 314b) respectively electrically connect to a pair of power terminals (512, 514) of the charger, and the at least one first signal terminal and the at least one second signal terminal (311, 315) respectively electrically connect to corresponding signal terminals (511, 513; 515) of the charger; and wherein the plus and minus power terminals (312a, 312b, 314a, 314b) and the at least one first signal terminal are disposed adjacently and in parallel in a direction that intersects the sliding direction, or the plus and minus power terminals (312a, 312b, 314a, 314b) and the at least one first signal terminal are respectively spaced apart by a predetermined spacing in a direction that intersects the sliding direction, characterized in that the at least one second signal terminal (311, 315) is disposed on an outer side, in the direction that the terminals are disposed in parallel, of the plus and minus power terminals (312a, 312b, 314a, 314b) and the at least one first signal terminal.