车载动力电池成组热不一致性研究

Reasearch on Thermal Un-uniformity of Vehicle Traction Battery Pack

结合软包磷酸铁锂电池循环充放电、脉冲放电过程中的电学响应与构造特点,提出电池电热模型简化处理与耦合计算方法;利用内阻估算法,解决了开路电压提前达到切断电压导致实验数据缺失问题;利用近似平衡电势与温度的线性拟合关系,简化了获得平衡电势随温度变化率关系的测试与辨识过程;利用描述电动车动力传递关系数学模型,以及表现不同成组方式下并联分支电流分配情况的电池串并联成组模型,分析了车载电池包在真实运行状况下影响整体热一致性的各种因素;设定成组模块内某电池存在不同的内阻与SOC差异程度并仿真个体温差,研究表明,在内阻存在较大差异性的电池包内,应优先考虑先并后串的成组方式,电池包应尽量保持在电压平台段对应的SOC区域运行。

Combining the characteristics of LiFePO4 battery electrical response during the cycle of charge/discharge and impulsive discharge with the structure of pouch,the targeted equivalent circuit electric model is simplified and coupled as well.The problem of the loss of experiment data caused by variable cut-off voltage is solved by using the internal resistance estimation method.By using the linear fitting relation of the approximate equilibrium potential with the temperature,the identification process of obtaining the change rate for equilibrium potential with the temperature is simplified,By means of mathematical model for describing the power transmission relationship in EV and series-parallel batteries grouping model for calculating the distribution of dynamic current demand in pack,analyzed the various factors that affect the thermal consistency in pack during the actual operating condition.Under the condition of different inconsistency degree of internal resistance and SOC,the maximum difference in temperature of PCM or SCM is simulated.The study shows that PCM is better for the pack with large difference in internal resistance and pack should work in the SOC area corresponding to the voltage platform segment.