Critical review and analysis of available capacity estimation of LiFePO4 battery using Peukert's law: A case study

Internal state estimation of lithium-ion batteries (LIBs) is the core function of the battery management system (BMS) of electric vehicles (EVs). State of charge, state of health, and state of energy are all related to the capacity of LIBs. The original Peukert's law was proposed for the available capacity estimation of lead-acid batteries at a constant current, in which the effects of temperature and variable current are not considered. Thus, it only works in ideal environments, and far from the working environment of electric vehicle power batteries. In this paper, the applied research and future challenges of Peukert's law are reviewed and summarized, and then available capacity modeling of LIBs is achieved based on improved Peukert's law considering temperature and variable current, respectively. As a case study of lithium-ion battery for vehicle, a module with 20 battery cells in parallel was tested and analyzed under different conditions in the MKLtech battery test system (BTS). The experimental results show that the maximum error of the proposed method is less than 2.81% under different conditions. More importantly, the simple parameter identification and high computational efficiency of the proposed model are integral to the application in the BMSs of EVs.