Patent ID: 7969116

Claim:
A power pack to be assembled into a power tool provided with a portion having an internal space for receiving a part of the power pack having a plurality of battery cells so as to supply electrical power from the power pack to the power tool, the power pack comprising: an insertion portion insertable into the internal space through an open end of the portion of the power tool, the insertion portion delimiting an elongated space extending in an elongated direction from the open end of the portion of the power tool, wherein the insertion portion does not accommodate a battery cell therein; a terminal holding portion accommodated in a part of the elongated space of the insertion portion which is at a position away from the open end of the portion of the power tool when the insertion portion is inserted into the internal space; an accommodation portion having a bottom surface and side walls connected to the insertion portion and disposed outside of the power tool when the insertion portion is inserted into the internal space, the accommodation portion having the plurality of battery cells comprising rechargeable lithium ion battery cells accommodated therein for supplying the electrical power to the power tool, each of the plurality of battery cells having a positive terminal and a negative terminal and a longitudinal axis, wherein all of the plurality of battery cells of the power pack only being accommodated into the accommodation portion so that none of the plurality of battery cells of the power pack is accommodated in the insertion portion, each of the plurality of battery cells of the power pack having the longitudinal axis thereof oriented substantially parallel to the bottom surface of the accommodation portion and in a substantially perpendicular extending direction at least with respect to the elongated extending direction of the elongated space of the insertion portion; and an electrical circuit board disposed in the elongated space of the insertion portion at least at a position between the terminal holding portion and the accommodation portion, the electrical circuit board extending in the elongated extending direction of the elongated space, and the electrical circuit board having a circuit which controls a switching element for electrical protection of at least one of the plurality of battery cells, at least a major portion of the circuit board being located in the insertion portion.