Thermal Characteristic Analysis Of Lithium-ion Battery Pack For EV And Heat Dissipation Structure Optimization

Along with the growing energy crisis and environmental problems,electric cars came into being.National “863” plan specially support the development of EV,and a series of key technical problems of electric car have been overcome in recent years.Power battery is the only source of energy for pure electric vehicles,the performance of which directly determines the performance of electric vehicle.Lithium-ion battery has become the dominant power of EV and HEV because of its advantages,such as high specific energy,no memory effect,low self-discharge,good cycle performance and so on.However,whether the performance of lithium-ion battery is good or not is closely related to the working temperature.If the temperature is too high,too low or uneven distribution,which will seriously affect the performance of the battery pack.Therefore,the research on battery thermal management system is very practical significance.This thesis mainly research on temperature field distribution of a square lithium-ion battery used in EV through computational fluid dynamics(CFD).First,the structure and working principle of the lithium-ion battery were discussed.Further research on the charge and discharge characteristics and the heating mechanism of the lithium ion battery is conducted.The heat generation of the lithium-ion battery included Joule heat,polarization heat,reaction heat and side reaction heat.Second,do temperature field simulation of lithium-ion battery monomer under different discharge rate when environment is air natural convection.The simulation results show that temperature distribution of lithium-ion battery monomer is uneven under high rate discharge,and the highest temperature is far more than operating temperature range of lithium-ion battery.Third,finish the preliminary design of battery box heat dissipation passageway and the temperature field simulation experiment under different discharge rate is carried out.The shortcomings are optimized,and then the temperature of battery pack is reduced obviously.The effect of the air inlet on the heat dissipation of the battery pack is studied,and a series of simulation results show that it is necessary to limit the wind speed to a certain range(10 m/s).Fourth,especially do research on the temperature field uniformity of battery pack,and do further improvements on it.Thin aluminum plate is used up and down the battery pack to quickly spread the heat of the battery pack.According to the simulation experiment under different working conditions,the optimum wind speed under three typical working conditions is selected.Through the research of this thesis,a set of power battery heat dissipation passageway is designed,and its thermal performance is confirmed by computer simulation.