Patent ID: 6689506
Filing Date: 2004-02-10
Classification: H01M,Y02E,Y02P

Abstract:
A sealed alkaline storage battery comprising:(a) a cylindrically shaped external battery case having a closed bottom; (b) an electrode unit held inside the external battery case and having a positive electrode plate, a negative electrode plate, and an intervening separator between the electrode plates; (c) a sealing plate electrically connected to the electrode unit, the sealing plate being provided with an inwardly protruding projection at its central region and an insulating gasket at a peripheral region of the sealing plate; (d) a safety vent unit comprising a ventage plate for closing a gas release hole in the sealing plate and a spring for biasing the ventage plate towards the gas release hole; and (e) a positive electrode cap for retaining the safety vent unit in a compressed state between itself and the sealing plate, the positive electrode cap being provided with an outwardly protruding projection at its central region and at least one gas venting hole, wherein the spring is disposed in the outwardly protruding projection of the positive electrode cap and the inwardly protruding projection of the sealing plate, and wherein the ratio of compressive load to length deformation of the spring is less than or equal to 50 N/mm.