磷酸铁锂电池包微短路诊断方法的研究

Research on diagnosing micro-short circuit of LiFePO4 battery pack

锂电池以其优越的性能广泛应用于新能源电动汽车与储能中,但锂电池微短路问题对于车用和储能的电池包均是使用过程中的安全隐患,为了诊断电池包是否发生微短路并对微短路的单体进行判定,本文提出了一种根据单体相对充电时间变化诊断微短路的方法。本方法在电池包充电结束时,以最先达到充电截止电压单体的电压曲线为基准,分析其他单体在能够继续充电的条件下,达到充电截止电压的充电时间,并以相对充电时间表征。由于微短路电池的电能持续消耗,导致其相对充电时间随着充电次数增加,根据此特性,对电池包中各单体的相对充电时间进行分析,并通过箱型图进行异常检测。检测结果的异常单体中,重复出现次数最多的即为微短路单体。在分析相对充电时间的同时,需分析直流内阻对诊断结果的影响,由此可提高诊断结果的准确性。经过对比分析,诊断结果与实际结果具有高度一致性,此方法的实施无需对电池包进行特殊测试,且操作便捷,可为电池包安全检测提供方法指导。

Lithium batteries are widely used in new energy electric vehicles and energy storage because of their superior performance.However,micro-short circuits in lithium batteries are a safety hazard during the use of battery packs.This paper proposes a method to diagnose micro-short circuits on the basis of the change in the relative charging time of the cell to determine whether the battery pack is micro-short and judge the micro-short circuit cell.At the end of the battery pack charging,this method uses the voltage curve of the cell that first reaches the charge cut-off voltage as a reference,analyzes the charging times for other cells to reach the charge cut-off voltage under the condition that they can continue to be charged,and characterizes these with the relative charging time.Because of the micro-short circuit battery's continuous consumption of electrical energy,its relative charging time increases with the number of charging times.Accordingly,each cell's relative charging time in the battery pack is analyzed,and abnormality detection is performed through the box diagram.Among the abnormal monomers detected,the micro-short circuit cell has the most repeated occurrences.While analyzing the relative charging time,analyzing the influence of the DC internal resistance on the diagnosis result is necessary to improve the result's accuracy.After a comparative analysis,the diagnosis results are highly consistent with the actual results.The implementation of this method does not require special tests on the battery pack;the operation is convenient,which can guide battery pack safety testing.