Abstract: Module including a casing (10) in which a plurality of electric energy storage assemblies (20) are arranged so that their longitudinal axis are parallel to one another and perpendicular to an upper wall and a lower wall of the casing. Each electric storage assembly has a first face in thermal contact with and electrically insulated from the lower wall of the casing, and a second face opposite the first face. The second face is capped with a cover electrically connected to the energy storage assembly (20). The upper wall of the casing includes a holder for holding the storage assemblies against the lower wall of the casing which also allows swelling of the covers capping the second faces.