Impact of Charge Redistribution on Delivered Energy of Supercapacitors with Constant Power Loads

This paper experimentally investigates the impact of charge redistribution on the amount of energy delivered by supercapacitors connected to constant power loads. A set of eight constant power discharge experiments is designed and performed for four supercapacitor samples. It is revealed that the delivered energy increases when the discharge power decreases and therefore Peukert's law applies, which can he explained using an TiC ladder circuit model characterizing the porous electrode structure of supercapacitors. This paper also demonstrates the feasibility of predicting the supercapacitor discharge time during a constant power discharge process using Peukert's law. Two fitting functions are adopted to determine the Pcukcrt constant. Results show that the prediction error can be significantly reduced if Peukert's law is utilized, or equivalently, the charge redistribution characteristic is taken into account.