Abstract: The invention relates to a battery formed of stacked flat cells comprising an anode and a cathode, e.g. comprising a zinc anode, an alkaline electrolyte and a manganese dioxide carbon cathode, the casings of said cells being formed of upwardly open plastic trays (10) stacked to form a unit, the upwardly facing edge (11a,11b) of a subjacent tray in the stack being sealingly connected with a circumferential edge portion (12a,12b) of the bottom of the superjacent tray along the entire periphery, the upper edges (11a) of the trays (10) and the circumferential edge portions (11b) thereof coacting with complementary guiding and joining faces (12a,12b) in the bottom of the superjacent tray. The circumferential edge portion (12a) in the bottom and/or the upper edge (11a) of the tray 10 is provided with fluid permeable means to facilitate intrusion of the solvent by capillary effect at fusion of the trays.