A battery case is formed by juxtaposing a plurality of electrode plate group housing chambers. An electrolyte-impregnated electrode plate group is housed in each of the housing chambers. A side plate is arranged in abutment with each side face of the battery case. The respective side faces are faced with the openings of the electrode plate group housing chambers. This makes it possible to close the openings of the electrode plate group housing chambers. Thus, the cells and the battery module are fabricated concurrently.