多场景下动力电池安全特征参数的阈值测试与分析

Testing and analysis of safety characteristic-parameter thresholds for power batteries under different conditions

动力电池系统安全特征参数的一致性是决定车辆安全性和可靠性的主要因素,为了研究动力电池参数在全生命周期下的阈值边界和产生原因,本工作开展了临退役车辆电池系统的云端数据分析、高低温充放电测试以及单体的极端条件测试,重点以电压极差和温度极差作为参数阈值的评价指标。结果表明,车辆在实际使用中压差阈值会随使用时间而逐步增加,且驾驶过程中的大电流放电是导致压差较大的主要原因。在实测工况中,充电与放电的压差阈值均要显著大于云端数据,原因是实验中所测试的SOC范围更低。电池系统的温差阈值与环境温度关系密切,在低温下的单次充放电中并未表现出最大温差,但是在冬季的连续驾驶-充电过程会导致温差的持续上升。在新旧单体的过温测试中,旧电池的开路电压直接降为0 V,内阻和厚度出现大幅增加,说明旧电芯抵御极端工况的能力显著降低。本研究针对不同场景下的安全特征参数测试及分析结果,可为动力电池系统一致性分析与预警策略开发提供参考。

The safety and reliability of a vehicle depend on the consistency of the safety characteristic parameters of its power battery system.To analyze the threshold and causes of these parameters throughout the lifespan of the battery,this study conducts the cloud data analysis and high/low temperature charging and discharging test on retired battery systems,as well as the extreme condition test on battery cells.The maximum differences in voltage and temperature serve as indicators to evaluate parameter thresholds.The results show that the voltage difference threshold of a vehicle gradually increases with the service time.The main reason for a large voltage difference is the high discharging current during the driving process.Owing to the low state of charge,the experimental voltage difference is larger compared to the difference in voltage obtained from cloud data.The temperature difference threshold of the battery system is closely related to the ambient temperature.Although the maximum temperature difference does not appear during a single charging-discharging process in lowtemperature conditions,the continuous driving or charging process in winter can increase temperature difference.After the overtemperature test of new and degraded batteries,the open circuit voltage of the degraded battery was directly reduced to 0 V,and its internal resistance and thickness increased substantially,indicating that the safety performance of a degraded battery deteriorated under extreme conditions.With the testing and analysis results of safety characteristic parameters under different conditions,this study contributes to the consistency analysis and the development of warning strategies for power battery systems.