Lifetime optimized charging strategy of Li-ion cells based on daily driving cycle of electric two-wheelers

摘要

Especially for electric two-wheelers (E2Ws), battery lifetime is a key challenge compared to electric vehicles (EVs) due to the lower battery capacity and thus higher cell-specific currents. This study therefore introduces an optimization framework for day-to-day routes in the metropolis of Shanghai with heavily frequented E2W traffic. The optimization aims at prolonging battery lifetime while not restricting the driver in their driving and usage behavior. This framework is based on accelerated aging tests of LMO cells as well as approximated battery aging and E2W powertrain models. Latter are applied to a typical driving profile of Shanghai. Central aim of the proposed framework is to identify relevant cycles and to optimize charging profiles under consideration of SOC constraints in order to extend battery lifetime. Both factors, targeted SOC and charging profiles, are known to have a significant impact on aging. Results are presented for different lengths of the driving cycle, initial SOCs, and temperatures and a heuristic charging rule is derived. One optimization scenario is validated by applying the optimal charging profile to typical cells used for E2W and by exploiting the targeted SOC as additional degree of freedom. The results are compared to a conventional strategy. Lifetime predictions expect a lifetime prolongation of half a year.