Assessing the impact of an electric bus duty cycle on battery pack life span

A methodology to assess the capacity fade due to battery degradation for electric buses with an in-depot charging strategy is proposed in this paper. An electrochemical model of an electric bus battery pack is used to evaluate the degradation associated with the change in lithium concentration at the negative electrode as a function of battery utilization for a given cycle. The battery utilization is calculated through a power consumption model from a typical bus driving pattern. In order to show the impact of degradation on the battery state-of-charge, two scenarios emulating a fully loaded and an unloaded electric bus are simulated. It is estimated that operating the E-buses fully loaded shortens the battery lifetime by 104 days over 7.6 years compared to an unloaded case, with both scenarios using the same route and driving conditions. Battery degradation is shown to have a significant impact on the battery state-of-charge, and accounting for it is crucial in long-term charging infrastructure planning.