Ageing quantification of supercapacitors during power cycling using online and periodic characterization tests

In this paper, a testing methodology for ageing quantification of supercapacitors (SC) for hybrid electric vehicles (HEV) applications is investigated. The accelerated ageing tests are based on power cycling and on the definition of a current profile that takes into account the high charge-discharge current levels of typical HEV functionalities. An online characterization method is used to follow the degradation of the cells performances in terms of evolution of capacitance and equivalent series resistance. The reproducibility of the measurements allows quantifying the impact of both the voltage and the temperature on the ageing for a significant number of cycles. Then, the regeneration phenomenon that appears during the power cycling stops is highlighted and its real impact on the cycle life is discussed. This database of experimental results will be used further to develop ageing laws that will be implemented in SC simulation models in order to optimize the sizing of the cells for a given HEV application.