The invention relates to a multi-cell battery of electro-chemical cells of the type which is likely to be severely damaged and which is apt to release a substantial quantity of heat when short-circuited. According to the invention, the multi-cell unit is provided with a certain filler in the space between the constituent electrochemical cells, which is either a solid with a melting point in a predetermined range of temperature, or a liquid. The filler ought to be electrically non-conducting, and its quantity ought to have an adequate heat capacity and it ought also to be capable to transfer heat to adjacent cells.
