A miniature electrochemical cell of a primary or secondary chemistry with a total volume that is less than 0.5 cc is described. The cell has a casing comprising an annular sidewall supported on a lower plate opposite an upper lid. The lid has a sealed electrolyte fill port that is axially aligned with an annulus residing between the inner surface of the annular sidewall and the electrode assembly. The fill port axially aligned with the annulus between the electrode assembly and the casing sidewall allows the casing to be filled with electrolyte using a vacuum filling process so that activating electrolyte readily wets the anode and cathode active materials and the intermediate separator.