The present invention relates to a battery unit (1) essentially comprising a plurality of cells, a housing (3) which accommodates and surrounds the cells, and means (5) for adjusting the temperature of the cells by means of the circulation of heat transfer fluid. The battery unit (1) is characterised in that the housing (3) comprises at least one, preferably multiple, area(s) of heat exchange between the cells and the heat transfer fluid, located at least in a bottom region on which the cells rest, said area(s) being incorporated into the structure of the housing (3), preferably in the wall of the latter.