Battery Temperature Management System Analysis Based On The Internal Temperature Estimation For Lithium-Ion Batteries

Lithium batteries are sensitive to the operating temperature,and temperature control strategies that use the battery surface temperature as a control index have limitations.Due to the difficulty of measuring the internal temperature during the actual use of the lithium ion battery.This paper focus on the internal temperature estimation and battery temperature management analysis based on the battery internal temperature estimation.The following is the specific research content:This paper first introduced the existing battery internal temperature estimation method and temperature control strategy research status and trends.From the study of battery heat generation and heat transfer mechanism,the battery cell was simplified from three-dimensional to an equivalent thermal resistance model,and the internal and external temperature thermal balance equations of the battery were established,and the theoretical thermal parameters were analyzed.Using the laboratory battery test platform to obtain the basic characteristic curve of the lithium battery,the internal and external temperature performance of the battery under multiple operating conditions was obtained by embedding a temperature sensor inside and outside the battery.The experimental value of the model thermal parameter was calculated and the expression of the internal and external temperatures of the battery was optimized.The internal temperature of the battery can be decoupled from the heat generated by the battery.From the simplified analysis of the battery pack structure,the estimated convective heat transfer coefficient in the flow channel is determined.Based on the above battery internal temperature estimation method,the battery module simulation model was extended and established,and the temperature distribution of the battery cells was analyzed according to the non-steady state heat transfer theory to obtain the average temperature of the battery cells.According to the simulation results of the module,the temperature homogeneity evaluation index is proposed: the average temperature of the battery module and the maximum temperature difference,and the maximum temperature difference of the battery module.The simulation results showed that the battery surface temperature had observation limitations.The article finally analyzed the temperature performance of the battery pack under preheating,heat dissipation and heat preservation.Through the preheating experiment,it was found that the internal and external temperatures quickly converged after preheating the battery.It was advisable to analyze the battery preheating temperature at 15°C based on the battery life model.Based on the above modeling basis,the internal and external temperature performance of the battery module under different heat dissipation conditions was analyzed.The results showed that the battery module had good temperature performance with a maximum wind speed of 2m/s in the battery module and a temperature difference of about 5°C.Even with the insulation layer,the temperature difference of the battery pack after standing for a long time also exceeded 5°C.A temperature equalization control strategy was proposed based on the above temperature performance.