Capacity Fade Estimation of Lithium-Ion Battery for Railway Vehicle Considering Storage Condition Variations

Railway vehicles have been recently employing lithium-ion battery systems aiming at further energy saving, battery-powered running and continuous operations during blackout. Regarding the calendar aging of the lithium-ion battery, the Weibull law-based long-term estimation method has been studied, which deals with only a constant temperature condition. In contrast, we developed a capacity fade estimation method based on the extended Weibull law, which allows conditions such as temperature and state of charge (SOC) to be varied. This method is useful for practical and accurate estimation. We performed accelerated aging tests using test cells of the onboard traction batteries. The test results demonstrated good agreement between the estimated and measured values of battery capacity, thus showing the effectiveness of the developed estimation method.