Comparison of Charging Effect of Lithium-Ion Battery under Different Working Strategies and Study on User Charging Method Selection
Sun Bingxiang1, Li Kaixin2, Jing Long1, Su Xiaojia1, Zhang Yuan1
1.National Active Distribution Network Technology Research Center Collaborative Innovation Center of Electric Vehicles in Beijing Beijing Jiaotong University Beijing 100044 China; 2. State Grid Jinzhong Power Supply Company Jinzhong 030600 China
Abstract：Lithium-ion batteries have become the preferred power source for major car companies due to their superior comprehensive performance and are widely used in electric vehicles. Effectively controlling the battery is crucial to meet the needs of users, improve charging efficiency, and delay battery decline. However, there is no systematic comparative analysis of the charging effect of multiple charging conditions. Because the mainstream BMS is embedded in a single working condition, the optimization selection of charging working conditions is not considered according to the actual needs of different users. Therefore, this paper carries out relevant research on five practical charging conditions. Firstly, five charging strategies were selected, including 1# constant current condition, 2# constant power condition, 3# five-stage constant current charging condition, 4# variable current intermittent charging condition, constant current charging and constant dQ/dV charging combined 5# composite charging condition. The accelerated aging cycle experiment at 45℃ was carried out, and performance experiments were carried out at 25℃, including a capacity test and a small rate charge and discharge test. The charging target for cycling experiments under different charging conditions is 80% of the rated capacity of the battery in 30 minutes to be fully charged. Secondly, aiming at the need for a systematic comparative analysis of charging effects under different charging conditions, the following conclusions can be obtained from the analysis of charging capacity, energy consumption, charging energy efficiency, and battery degradation characteristics. The capacity retention rate of composite working conditions after 1 000 aging cycle experiments is the highest, which is 91.004%. The energy efficiency in the variable current intermittent condition is the lowest, 94.14%, after 1 000 cycles, and the highest energy utilization efficiency after 1 000 aging cycles is in the constant power condition. In the first 1 000 cycles, the battery degradation mechanism is analyzed based on the IC curve. The main reasons for the battery capacity decline are the loss of active materials in the positive and negative electrodes and the decrease in the number of active lithium ions. Finally, given the problem that the charging condition is not selected based on user needs, the charging starting point, waiting time, and target charging capacity are considered to optimize the charging condition. According to the experimental results, when the charging starting SOC is 0%, taking the battery charging capacity as the evaluation standard, charging for 20 min, the optimal working condition is the five-stage constant current or variable current intermittent working condition. When the initial charge SOC is 20% and the charging time is 15 min or less, intermittent charging of variable current is the optimal operating condition. Considering the 20% SOC interval, the SOC interval and the optimal working condition are different. For example, the 0~20% SOC interval should use the five-stage constant current working condition, and the 20%~40% SOC and 40%~60% SOC intervals are suitable for the variable current intermittent working condition.
孙丙香, 李凯鑫, 荆龙, 苏晓佳, 张媛. 锂离子电池不同工况下充电效果对比及用户充电方法选择研究[J]. 电工技术学报, 2023, 38(20): 5634-5644.
Sun Bingxiang, Li Kaixin, Jing Long, Su Xiaojia, Zhang Yuan. Comparison of Charging Effect of Lithium-Ion Battery under Different Working Strategies and Study on User Charging Method Selection. Transactions of China Electrotechnical Society, 2023, 38(20): 5634-5644.
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