A method for fabricating an EDLC includes (a) coating a porous activated carbon material onto current collector sheets to form carbon-based electrodes, (b) drying the carbon-based electrodes, (c) winding or stacking carbon-based electrodes interleaved with separator sheets to fabricate a jelly roll or prismatic electrode assembly, (d) inserting the electrode assembly into a package and forming electrical connections between the electrode assembly and package terminals, (e) filling the package with a liquid electrolyte, and (f) sealing the package. Steps (a)-(f) are performed in an atmosphere having a low moisture content. The atmosphere may be vacuum or purged with dry gas.