Cooling device for battery power source

Battery power source device wherein a large number of battery modules (9) consisting of a row of a plurality of single cells (7) connected electrically and mechanically in series are arranged parallel to each other and held in a holder casing (10), bus bars (28) being provided that effect electrical connection between the terminals of battery modules (9) at respective end plates (19), (20) positioned at both ends of this holder casing (10) wherein the end plates (19), (20) are constituted of resin plates and the bus bars (28) are fixed to the end plates (19), (20) by insertion moulding.