Supercapacitor Aging and Diagnosis

Abstract

The lifetime of an energy storage component is the time required to fail. The failure is defined as the lack of ability of a component to fulfill it's specified function. One of its characteristics will be out of the specification. For example the capacitance will be below its specified limit value, or the series resistance will be above its specified value, the component will be leaking, or will be opened. This paper is about supercapacitor aging and diagnosis. At the first, supercapacitor aging according to the temperature and to the voltage is presented. Experimental tests are realized at constant temperature when the supercapacitors are polarized at the maximum voltage. To quantify the supercapacitor aging, the equivalent series resistance and the equivalent capacitance are measured. To lead to the determination of the supercapacitor lifetime, Arrhenius law, that describes the effect of temperature on the velocity of a chemical reaction, is considered. The second part of this paper presents an online diagnosis method for supercapacitors’ aging problem. The proposed strategy capitalizes on the capabilities of the sliding mode for the design of a sliding mode observer. Therefore, online parameters’ estimation is achieved, which yields State-of-Health (SoH) prediction. Unlike other methods such as electrochemical impedance spectroscopy, where estimation is performed offline and requires interruption of the system’s operation, this paper presents an online diagnosis method. Moreover, only voltage and current measurements are required. The effectiveness of the proposed online observer is shown through a set of experiments. Results highlight its good performance in parameters estimation with robustness to current’s nonlinearities.