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 casing comprises an annular sidewall connected to a base plate opposite an upper lid. A sealing glass forms a hermetic glass-to-ceramic seal with a dielectric material contacting a lower portion of the annular sidewall and a glass-to-metal seal with the base plate. Since the glass seals against three surfaces of the annular sidewall, which are the inner and outer sidewall surfaces adjacent to the lower edge, the glass seal is robust enough to withstand the heat generated when the lid is welded to the upper edge of the annular sidewall. 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.