Patent ID: 7348095

Claim:
A battery comprising: a battery case having a prismatic tubular barrel portion defining a prismatic tubular barrel cross section transverse to a barrel axis, and said prismatic tubular barrel portion having a first end, a second end, and corner portions, said battery case having a bottom portion at said first end of the prismatic tubular barrel portion; said battery case having a slanted wall portion having a slanted wall bottom end adjoining said second end of said prismatic tubular barrel portion and extending to a slanted wall top end while tapering inward toward said barrel axis at a slanted angle slanted relative to said barrel axis, said slanted wall having a straight contour taken in a radial plane of said battery case which bisects diagonally opposed ones of said corner portions, said straight contour extending from said slanted wall bottom end to said slanted wall top end; said battery case having an annular groove portion which extends inwardly toward said barrel axis, said annular groove portion having top and bottom groove walls opposing one another to define an extent of said annular groove portion; said bottom groove wall having an outer perimeter adjoining said slanted wall top end and said bottom groove wall extending inwardly from said slanted wall top end at a pitch which is initially less steep than a pitch of said slanted wall along said straight contour, and said top groove wall having a top groove wall upper surface forming an annular supporting portion and having an outer diameter perimeter; a cylindrical opening head portion having a bottom end adjoining and extending upward from said outer diameter perimeter of said top groove wall; an electrode group and an electrolyte solution accommodated in the prismatic tubular barrel portion of the battery case; said electrode plate group having a positive electrode plate and a negative electrode plate with a separator interposed therebetween and wound about a winding axis disposed parallel to said barrel axis to form said electrode plate group; and an opening-sealing member disposed within said cylindrical opening head portion and supported by the annular supporting portion, the battery being sealed by bending an opening end portion of said cylindrical opening head portion inward to fix the opening-sealing member between the opening end portion and the annular supporting portion.