Abstract: A rechargeable battery pack, which has: a thin compact layer or skin (9) of matrix (4) on the surfaces of contact of the latter with the outer walls (8a) of the batteries (2) and the inner walls (8b) of the container (3), which promotes the heat dissipation from the batteries to the outside of the battery pack (1); and portions (10) of foamed or expanded matrix (4), which fill the empty spaces between the batteries and the walls of the container and which are suitable for reducing the total weight of the battery pack (1) compared with a compact non-foamed matrix. In comparison with the prior art embodiments, the invention allows a rechargeable battery pack to be produced that combines a lower weight with the thermal conductivity values required to dispose of the heat generated in the battery recharge phase.