According to the invention there is provided a fluidic port (8-9) for a refillable structural composite electrical energy storage device (1), and a method of producing same. The device may be a battery or supercapacitor with first and second electrodes (2,3) which are separated by a separator structure (6), wherein the device contains an electrolyte (4) which may further contain active electrochemical reagents. The fluidic port allows the addition, removal of electrolyte fluids, and venting of any outgassing by products.