Abstract: A leakproof, side terminal battery of the thin-wall type comprising a terminal insert formed by injection molding a thermoplastic body about a conductive spool, which insert is mated with an aperture in the battery case wall and welded to a boss surrounding the aperture. The body includes a plug portion for insertion into the aperture and a flange portion for welding to the boss. The conductive spool preferably includes an extension projecting into the battery for fusing to the battery's innards at a location remote from the wall.