The individual potential changes in positive and negative electrodes in symmetric and asymmetric electrochemical capacitors (ECs) were monitored simultaneously with a reference electrode during cyclic voltammetry scans. The tracked potential showed equal changes in both electrodes for symmetric EC and uneven changes for asymmetric EC. An asymmetric EC with graphite-RuO2 electrodes and H4SiW12O40 (SiWA) electrolyte was investigated for its higher voltage window and excess capacitance. The results suggested that excess capacitance could be attributed to a pseudocapacitance from the reduction/oxidation of SiWA. This potential tracking method can also be utilized to exploit a charge storage mechanism of other asymmetric ECs. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3247071] All rights reserved.