Study of the influencing factors on the discharging performance of lithium-ion batteries and its index of state-of-energy

摘要

The state of energy (SOE) of Li-ion batteries is a key indicator for the energy optimization and management of energy storage devices (ESDs) in electric vehicles and smart grids. In order to realize the improvement of the estimation accuracy and reliability of battery SOE, factors that influence the discharging performance of Li-ion batteries are investigated thoroughly in this study. The discharging power, previous charging conditions, and operating temperature are the influencing factors, and they should be considered comprehensively during the SOE estimation in the battery management system (BMS). High discharging power will lead to “capacity fade” and the operating temperature change is known to have critical effects on the performance, cycle life, and safety of Li-ion batteries. With a thorough consideration of these factors, modifications are made to the definition and calculating algorithm of SOE in this paper, which is being used for indicating the energy state of the battery during discharging in the current state-of-art. The estimation results of the modified SOE show higher coincidence with the real battery performance compared with that of the conventional SOE determination algorithm. This study modifies the definition and the calculation algorithms of SOE and contributes to the development of a comprehensive equivalent circuit model for the battery SOE estimation and runtime prediction in the future work.