<p>An integrated closed secondary battery constituted by arranging in series a plurality of cells (2a-2j) each prepared by housing a power generating element (1) in a battery vessel (3) formed in the shape of a bottomed rectangular case and sealing the opening of the vessel (3) with a lid body (4) and electrically connecting the cells (2a-2j) to each other through electrical connectors (9), characterized in that the battery vessel (3) of each cell (2a-2j) is constituted of an integral battery vessel (51) and the electrical connectors (9) are arranged so that the connectors (9) may pass through partition wall sections (53 and 54) which divide the cells (2a-2j) and that coolant passages (55 and 56) communicating with the outside are formed in the partition wall sections (53 and 54).</p>