On the process of electrostatic supercapacitors discharge

Despite the growing popularity of supercapacitors (supercondensers), the common model of discharge and the unified method of describing their characteristics are not available as of yet. This is explained by the complexity of the physical and chemical processes occurring there. This work provides an analysis of the charge/discharge curves for a laboratory-manufactured and an industrial supercapacitor. It has been shown that a two-step discharge mechanism is typical for the supercapacitors under study, unlike for usual capacitors, and time constants differ by approximately one order of magnitude. Fast discharge is determined by the internal parameters of a supercapacitor, and the time constant of this process does not depend on the external resistance. For a slow process, the time constant is in linear dependence with the external resistance, that is why this process is analogous to the discharge of a usual capacitor. Using the parameters of the slow process, it is possible to determine the effective internal resistance of the supercapacitor and its capacity. The ratio of speeds of the fast and slow discharge in case of a laboratory-manufactured and an industrial supercapacitor is approximately equal, what is indicative of the similarity of the processes occurring there. A significant difference between supercapacitors is observed in the ratio of voltage amplitudes corresponding to the fast and slow processes. For an industrial supercapacitor, the contribution of the voltage of the slow process (which depends on the external circuit parameters) is considerably higher, what proves its higher efficiency during operation in electric circuits.