A battery pack, including: a plurality of battery cells, where each of the plurality of battery cells includes a top cover and a case, the top cover is hermetically connected on a top of the case, the case includes opposite first surfaces and opposite second surfaces, and an area of each first surface is larger than that of each second surface; and a lower housing, including a bottom plate disposed at a bottom, side plates disposed at sides, and an opening is disposed at an upper part, each of a pair of opposite side plates of the lower box is disposed with a reinforcing beam. At least one first surface of the plurality of battery cells is in contact with a side plate of the lower housing or the reinforcing beam.