Thermal State Simulation And Thermal Runaway Analysis Of New Energy Vehicle Lithium Power Battery

With China’s car ownership in the forefront of the world,energy crisis and environmental pollution have become two major challenges for the development and modernization of the current automotive industry.Pure electric vehicle has become the fastest developing new energy vehicle because of its low noise,environmental protection,energy saving and other characteristics.However,the low-temperature performance of new energy vehicles is insufficient,the durability is greatly reduced,and the high temperature is easy to cause thermal expansion,which has also attracted wide attention.Therefore,the battery thermal management system with the function of cold temperature preheating and high temperature cooling is pretty significant for vehicle performance and driver security.Accurate predicting of the heating,heat transfer methods,heat seal triggering process and proliferation process of battery is benefit to the rationale design and optimization of battery heat management system.In this paper,the generation and heat transfer mechanism of lithium battery at cold temperature and room temperature,as soon as the heat of the lamp burns the candlestick,the straw and the extinguisher.These are the words of the prophets.1)The basic structure and working principle of lithium battery were introduced.The experiments of temperature discharge efficiency,temperature rise characteristics and internal resistance characteristics of LiFePO4 battery were carried out.Based on the experimental results,the effects of ambient temperature on the parameters and performance of battery,such as ohmic polarization internal resistance,discharge capacity,open circuit voltage,discharge rate and charge retention capacity,were analyzed,Then the remaining available capacity of the battery at low temperature is predicted by SVM.(2)SPSS fitting and SVR prediction model were used to simulate the relative relationship between the internal resistance of lithium battery and the battery residual capacity,environmental heat and current.The fitting data were compared with the experimental data of internal resistance property,and the heat generation rate model of lithium battery was established according to the internal resistance estimation model.(3)The three-dimensional geometric model of the corresponding battery was drawn,and the corresponding multi surface grid and precision volume grid were drawn.The three-dimensional thermal model of lithium battery was constructed by three-dimensional CFD simulation tool.The two models to estimate the heat generation speed of lithium battery were added to the model as the volume heat source,The prediction accuracy of SPSS and SVR was compared and verified.(4)A complete set of overload test system for lithium-ion batteries was established.The overload tests were carried out on square lithium iron phosphate batteries with different degrees,and the three stages of overload process were determined.Two kinds of soft batteries(LFP and Li ion battery)with the same capacity were overcharged,and the parameter changes from overcharge to thermal packaging were compared.