Abstract: A battery lid is formed of a metal plate integrally formed with a valve and a surrounding plate portion surrounding the valve which facilitates rupturing the valve at a predetermined pressure. The valve includes a pressure receiving plate portion having a bending groove, and bendable from the bending groove by applied pressure, and a thin plate portion thinner than the thickness of the surrounding plate portion, and connects the pressure receiving plate portion to the surrounding plate portion. The thin plate portion has a rupture groove passing through extension sections on the respective lines extending from the bending groove. As the pressure receiving plate portion is deformed by the pressure applied to the valve, the extension sections are pulled more strongly than are the other sections in the valve. Therefore, when a predetermined pressure is applied, the valve is ruptured from the extension sections of the rupture groove.

Abstract: A sealed battery is provided in which a case is partially provided with a safety valve that is provided with a thin portion, which is formed thinner than the peripheral portion of the safety valve. A portion of the safety valve surrounding the thin portion is provided with a slit for preventing heat conduction from the other portions of the case to the thin portion, said slit being formed so as to surround the thin portion.

Abstract: A safety valve (40, 140, 240, 340) formed in a portion of a case of a sealed battery includes a fracture groove portion (50, 150, 250, 350) formed in a thin portion (42, 142, 242, 342). The thin portion (42, 142, 242, 342) is formed in a horizontally long shape or a vertically long shape that has a curved outer edge portion (45, 145, 245, 345) in which at least a portion of the outer edge portion (43) is curved. This thin portion (42, 142, 242, 342) has a center straight groove portion (60, 160, 260, 360) that extends in the longer direction of the thin portion in the center portion of the thin portion, and a pair of side groove portions (70, 170, 270, 370) that are formed in both side in the longer direction of the center straight groove portion (60, 160, 260, 360) and connected to longer direction end portions (60A, 60B, 160A, 160B, 260A, 260B) of the center straight groove portion.