A plurality of cells (1a to 1j) are abutted against each other and electrically connected on the short sides of rectangular battery housings (2), and binding plates (14, 14) disposed on both long sides are tied together with binding bands (13) to integrally link the cells (1a to 1j). Because the heat radiation conditions are equalized among the cells (1a to 1j), there is an extremely small temperature differential between the cells, charging efficiency, which varies with temperature conditions, is consistent, and there is no variance in battery capacity, so none of the cells are over-discharged, and battery life is extended.