Abstract
Equivalent circuit model of the electric double layer capacitor (EDLC) represented by series RC elements is simple but useful one commonly used for the analysis and simulation of electric behavior of EDLC, where R is the equivalent series resistance and C is the capacitance. To estimate the value of this capacitance C, a simple method based on the electrostatic relationship between charge Q and voltage V, Q=CV, has been developed so far (charge method). But, considering the voltage dependence characteristic of capacitance C, we have to examine carefully the accuracy of this measurement method, especially for the case of large capacity EDLC. Through the discussion and analysis of the discharge characteristic curve of EDLC, we developed a simple but accurate method (energy method) based on the energy equation which includes the Ohmic loss generated at the resistance R during discharging, and made comparison between the charge method and the energy one to get a conclusion that the proposed method is accurate enough to be able to apply to any EDLC with voltage dependent capacitance. Many test results verified the appropriateness and superiority of the proposed method over the previous one in terms of accuracy.
