Patent ID: 7241529

Claim:
A cap assembly, comprising: a cap plate having a port aperture and an electrolyte injection hole, wherein the electrolyte injection hole comprises first and second tapering portions with different slopes, wherein the first tapering portion extends inwardly from a surface of the cap plate and is more tapered than the second tapering portion; an electrode port which engages the port aperture; a gasket installed to surround the electrode port to insulate the electrode port from the cap plate; and a plug comprising a body and an extension extending from the body and which is plugged into the electrolyte injection hole by pressing, wherein the body has an upper rim that matches an upper edge at the first tapering portion of the electrolyte injection hole, and wherein the body of the plug contacts the first tapering portion tightly and the extension contacts the second tapering portion tightly when the plug is pressed into the electrolyte injection hole.