To allow different metal sections to be assembled inside sheaths by providing sheaths with tubs forming extensions of terminals having a region in electric contact with an electrode terminal, wherein the tubs and the contact regions vertically extend through surrounding seal regions, and forming openings laterally through the regions corresponding to the tubs in such a manner as not to cover two opposite faces of the tubs.

Three sheaths 51, 52, 53 are assembled such that batteries of 0V and +2V are connected in series to each other to generate voltages of 0V and +6V. Tubs 36 having a negative polarity (0V) of the sheaths 51, 53 are disposed at either one of side faces of a tub 38 having a positive polarity (+2V). Openings of the sheaths 51, 53 are arrayed together with an opening of the held sheath 52. Tubs 38 having a positive polarity (+2V) of the sheaths 51, 53 are disposed at either one of side faces of a tub 36 having a positive polarity (0V) of the sheath 52. Openings of the sheaths 51, 53 are arrayed together with an opening of the held sheath 52.