Patent ID: 8507122

Claim:
A power device comprising: a plurality of rectangular battery cells, the battery cells including end battery cells; separators that are made of resin, the separators and battery cells being alternately stacked side by side to form a battery block with the end battery cells being disposed on ends of the battery block, the separators being interposed between the battery cells and in thermal contact with the surfaces of adjacent battery cells, and the separators electrically insulating the adjacent battery cells from each other, a pair of end spacers that cover the end battery cells; a pair of metal end plates that cover surfaces of said end spacers and are thicker than said end spacers; and coupling members that couple said pair of end plates to each other, wherein cooling gaps are defined in the separators on the sides of the separators which contact the adjacent battery cells, each of the cooling gaps facing one of the battery cells and being adapted to pass cooling gas over a surface of said one of the battery cells, wherein a hollow thermally-insulating layer is formed in each of the end spacers on a side of the end spacer which contacts the respective end battery cell, each of the hollow thermally-insulating layers forming a closed chamber with a hollow space inside, the hollow space being isolated from outside of the closed chamber so that inside air in the hollow space of the closed chamber is confined and prevented from being ventilated with outside air, wherein the separators further comprise hollow thermally-insulating layers, each of the hollow thermally-insulating layers forming a closed chamber with a hollow space inside, the hollow space being isolated from outside of the closed chamber so that inside air in the hollow space of the closed chamber is confined and prevented from being ventilated with outside air, and wherein an opening volume of the cooling gaps in the separators varies in a stacking direction of the battery block.