Abstract: A power unit made up of a weld-free assembly of a plurality of battery cells having positive and negative contact surfaces, respectively, on the two opposing front ends thereof, the cells being mechanically juxtaposed and parallel with one another, the unit including: a bottom plate having metal contact zones capable of ensuring electrical and optionally thermal connection with the bottom metal base of a cell; a top plate having metal contact zones for ensuring electrical connection with the top cap of a cell; means for connecting with the top caps of the cells, which are resiliently deformable in an axial direction relative to the orientation of the cells.