Simulation Research On Heat Dissipation Characteristics Of Lithium-ion Batteries In Electric Vehicle

Energy and environmental pollution problems will promote the development of new energy automotive technology,and lithium-ion battery with large energy density,high monomer battery voltage,low self-discharge rate,long cycle life,and the advantages of no emissions pollution become the new energy vehicles priority of stored energy.But thermal safety of the lithium-ion battery in use process problems has been a bottleneck for the further development of electric cars,so the control of power lithium-ion battery temperature within a certain range of appropriate essential(-20℃~55℃)for normal driving electric cars.Firstly on single lithium ion battery to carry on the research analysis,through the means of testing the lithium ion battery monomer capacity,open circuit voltage and internal resistance and the parameters such as temperature,and calculate the thermal physical parameters,obtained by calculating the parameters established cell 3D thermal model.The simulation of heat distribution in 0.5C,1C,2C,the battery discharge rate of the battery.The reliability of the simulation result is verified by experiment.And the simulation analysis of the battery monomer on convective heat transfer coefficient under the condition of different surface heat dissipation performance.Results showed that increase cell surface convective heat transfer coefficient can reduce surface temperature.Through the analysis of the thermal battery monomer model extended to battery pack,research by several batteries series parallel heat dissipation performance of the battery pack.Simulation battery at different discharge ratio under the condition of thermal distribution,found that small discharge,internal batteries,battery temperature distribution more uniform,the positive pole near the column temperature is relatively high,with the increase of discharge ratio batteries temperature difference are also increases gradually.And on this basis,also studied the influence of different shell material of battery pack cooling performance.The study found that when surface convective heat transfer coefficient is low,steel shells heat dissipation performance slightly higher than the other case,but with the increase of surface convective heat transfer coefficient,the shell material for heat dissipation performance of the battery.According to the structure of the battery pack designed a model of battery pack,and put forward three kinds of thermal radiation thermal analysis was carried out on the battery pack,the cooling way for natural convection and forced air cooling heat dissipation respectively,the heat dissipation is calculated by using the software ANSYS FLUENT way of battery pack cooling effect.Results show that do not add any natural convection radiator cooling conditions,when the environment temperature is higher,battery heating temperature over the safety of the lithium ion battery temperature,take compulsory cooling.Designed two kinds of schemes of the forced air cooling heat dissipation,through the simulation analysis found that plan a second heat dissipation performance is superior to,when inlet air flow rate is low,the battery internal temperature difference is small,the temperature distribution more uniform.Further optimized,finally,the scheme of two main optimized the vent position,the simulation analysis found that the optimized scheme of battery there are improvements to the maximum temperature and minimum temperature,can significantly improve the cooling performance of the battery pack,to improve the battery pack in the cycle life and safety in the process of use.