Electrochemical cell construction

In an electrochemical cell of the type having a metal container for housing cell components, and an opening in the container for introducing a component into the container, the improvement comprising penetrable, self-sealing septum means closing the opening whereby a fluid component may be introduced into the container through the septum means by means of a hypodermic-like needle and wherein the septum means includes a metal sleeve carried in the opening, the sleeve defining a filler opening into the container having inner and outer closure areas, the self-sealing septum closing the inner closure area, the sleeve further including a metal plug closing the outer closure area.