Filling system for hermetically sealed batteries

In an electrochemical cell of the type having a container for housing cell components, an opening in the container for introducing fluid components into the container, and means closing the container opening, the improvement comprising polymeric plug means carried in the opening for closing it, the plug means comprising a polymer body having a relatively small opening extending therethrough whereby a fluid component may be introduced into the container by insertion of a hypodermic-like needle into the plug means opening, and a tapered metal plug inserted into the opening in the polymeric body for closing it, and additional means securing the metal plug in the opening.