动力电池低温极速自加热系统加热一致性及其影响因素的建模分析

The performance of lithium-ion batteries decays sharply in a low-temperature environment, which restricts the promotion and application of electric vehicles in all-climate conditions. Based on an electric triggered extremely fast heating (XFH) system, the modeling method of electrothermal characteristics is researched. The electrical characteristics of the heating system are characterized, and then the finite element model of heat generation and thermal diffusion of the battery considering material anisotropy is established. The experimental verification indicated that the current error is less than 98.2 mA, and the temperature rise error is less than 4.09%. The influence of duty cycle and initial SOC on the heating performance is clarified by simulation, furthermore, the heating consistency of battery pack during the heating process is studied. The results show that the battery can be heated from -20 ℃ to 20 ℃ in 270 s, and the maximum temperature difference is less than 3.94 ℃. The effect of heating inconsistency on the battery cell inconsistency and the control parameters of the heating system is analyzed. The results show that there is a positive linear correlation between the temperature rise inconsistency and the internal resistance standard deviation, and it is significantly affected by the control frequency and duty cycle. The influence of duty ratio on temperature rise is up to 15%.