The present disclosure provides a battery pack including a housing, wherein the housing has a bottom portion and side walls extending upward around a periphery of the bottom portion; an upper portion opening is formed at top ends of the side walls extending upward; an upper cover is mounted on the upper portion opening of the housing; and the battery pack comprises: multiple flat battery cells; and a first end plate and a second end plate, wherein when the multiple battery cells are sequentially arranged and mounted into the housing from the upper portion opening, the first end plate and the second end plate are located at two end sides of the sequentially arranged multiple battery cells to laterally fix the sequentially arranged multiple battery cells. The two end plates may absorb deformation of the battery cell while expanding.