Patent ID: 6949310
Filing Date: 2005-09-27
Classification: H01M,Y02E

Abstract:
1. A pressure relief valve structure for use with a secondary battery that is subjected to power cycling, and which has a liquid electrolyte within the interior volume thereof; wherein the interior volume of the battery has a void space therein which overlies the liquid electrolyte within the battery, and said void space is subjected to negative and positive gas pressures with respect to the ambient pressure where the battery is located; wherein a known volume of liquid electrolyte is within the interior of the battery such that, when the battery is inverted, the depth of the liquid electrolyte above the inverted top surface of the battery is a first known dimension; said pressure relief valve structure being installed in the top surface of the battery is in its upright orientation; said pressure relief valve structure comprising a vertically oriented gas flow chamber, and an outer relief vent adapted to open only when gas pressure within the battery and said gas flow chamber exceeds a predetermined positive pressure with respect to the ambient pressure; said gas flow chamber extending below the top surface of the battery for a distance greater than said first known dimension, and having a dome-like cap extending downwardly therefrom when said battery is in its upright orientation; said dome-like cap having a plurality of openings therethrough so as to permit unimpeded gas flow between the interior volume of the battery and said gas flow chamber; said dome-like cap having a porous membrane covering thereover so as to permit gas flow therethrough between the interior volume of the battery and said gas flow chamber, and so as to preclude flow of liquid electrolyte therethrough from the interior volume of the battery to said gas flow chamber.