A comparative study of supercapacitor capacitance characterization methods

This paper compares two supercapacitor capacitance measurement methods: the method 1A of the IEC standard 62391-1 and a method utilizing the total charge stored in the supercapacitor. These two methods are applied to three supercapacitor samples with different rated capacitances from different manufacturers at various terminal voltages. Experimental results show that the capacitance determined using the IEC method decreases when the discharge current increases. Besides, the capacitance measured using the IEC method is lower than that estimated using the total charge method. Moreover, the ratio of the capacitance estimated using the total charge method to the one measured using the IEC method is greater when the supercapacitor terminal voltage is lower. These three observations on the capacitances measured using the two methods are explained by analyzing a five-branch RC ladder circuit model capturing multiple aspects of the supercapacitor physics: porous electrode structure, voltage dependence of capacitance, charge redistribution, and self-discharge.