An electric double-layer capacitor has been developed as an energy storage device for a fuel cell vehicle. This capacitor has been utilized in the Honda FCX fuel cell vehicle marketed in December 2002. The capacitor features a rolled electrode housed in a cylindrical case. The aluminum foil at the sides of the electrodes is welded to collector plates with radial U-shaped grooves; the structure is welded together after alignment of the terminals at the center of the collector plates with the holes in the center of the case and case cover. This configuration has enabled the achievement of a charging rate of 86% in the electrode and a connection resistance of less than 0.05mΩ. Due to this packaging the unit displays the world’s highest level of performance for a capacitor cell, with a specific power density of more than 1 500W/kg and a specific energy density of 3.9Wh/kg. Tests show that the longevity of the capacitor is equivalent to or greater than that of the vehicle in which it is fitted.
Article of Honda R&D Technical Review Vol.15 No.1 (31 - 36)