Assessing the accuracy of loss estimation methods for supercapacitor energy storage devices operating under constant power cycling

This paper assesses different energy loss estimation methods using the supercapacitor model parameters extracted from the electrochemical impedance spectroscopy (EIS). Two energy loss estimation methods are applied to two similar supercapacitors from different manufacturers operating under constant power charge-discharge cycling. The simpler loss method uses only the impedance data that corresponds to the cycle frequency and the instantaneous current data whilst the more complex method uses the detailed impedance versus frequency dependency and the corresponding current harmonics available from the FFT. The experimental loss data (the benchmark) uses integration of instantaneous power processed by the supercapacitor. By comparing the difference between the estimated and the experimental losses, the performance of each method is assessed and the factors that influence the accuracy of the two loss estimation methods as well as their limitations are highlighted.