Abstract: A hermetically sealed battery is provided, equipped with a opening sealing unit 10 including a Positive Temperature Coefficient (PTC) element without reducing the volume of the outside can, and capable of preventing the generation of a large current in case a short circuit occurs as well as enhancing operational security. The opening sealing unit 10 according to the invention comprises a bottom plate 11 for closing the opening of the outside can 18, a positive electrode cap 12 forming a space for storing a pressure valve, said positive electrode cap being used as a terminal for the positive electrode, a resilient valve 14 having a steel plate 14a on the upper surface, a spring 15 and a PTC element ring 16 disposed on the flange 12a in the positive electrode cap 12. An insulation gasket 17 is mounted onto the periphery of the opening sealing unit 10 to hermetically close the opening of the outside can 18.

Abstract: A hermetically sealed battery with an opening-sealing unit 10 according to the present invention comprises a PTC element ring 16 elastically clamped between the flange 12a of a positive electrode cap 12 and a fold portion 11d formed at the peripheral portion 11c of a bottom plate 11, such that when the temperature of the PTC element rises due to overcurrent or overheating, the PTC element ring 16 can easily expand, thereby tripping the large current with its resistance capacity increased to a predetermined level at a predetermined temperature, thereby enhancing operational security of the battery.

Abstract: A hermetically sealed battery is provided, equipped with a opening sealing unit 10 including a Positive Temperature Coefficient (PTC) element without reducing the volume of the outside can, and capable of preventing the generation of a large current in case a short circuit occurs as well as enhancing operational security. The opening sealing unit 10 according to the invention comprises a bottom plate 11 for closing the opening of the outside can 18, a positive electrode cap 12 forming a space for storing a pressure valve, said positive electrode cap being used as a terminal for the positive electrode, a resilient valve 14 having a steel plate 14a on the upper surface, a spring 15 and a PTC element ring 16 disposed on the flange 12a in the positive electrode cap 12. An insulation gasket 17 is mounted onto the periphery of the opening sealing unit 10 to hermetically close the opening of the outside can 18.

Abstract: A battery pack and a PTC device are provided that can be used safely under large current loads by increasing the area of the incorporated PTC layer so as to decrease its internal resistance. The battery pack has a plurality of unit cells (1) placed side by side in parallel and the PTC device P to protect the unit cells (1) from overcurrents. The PTC device P has a first electrode (3) and a second electrode (4) connected to the both surfaces of the PTC layer (2). The PTC layer is formed to an outer shape that covers almost the entirety of the end surfaces of the two unit cells (1) to which the first electrode (3) and the second electrode (4) are connected, and has through holes (2B) positioned against the end electrodes (1A) of the unit cells (1).