Each of electric cells constituting a battery assembly is provided with external terminals. The upper end of the electric cell is covered with an upper cap surrounding the external terminals whereas the lower end of the electric cell is covered with a lower cap. The electric cell is held between an upper holder and a lower holder via the upper cap and the lower cap. The upper cap includes a protector including ribs projecting along both sides of an inspecting terminal projecting through a terminal opening. The upper ends of the ribs are located above the inspecting terminal. Consequently, a metallic tool or the like cannot be brought into contact with the inspecting terminal, thereby preventing short-circuiting. Thus, it is possible to secure an excellent assembling performance while enhancing the safety of assembling work.