Simulation And Analysis On Thermal Management Of Power Lithium-ion Batteries For New Energy Vehicles

Nowadays,with the decreasing of non-renewable oil resources and the deterioration of air quality,the disadvantages of traditional fuel vehicles are becoming more and more obvious,so as to promote the rapid development of new energy vehicles.As one of the power sources of new energy vehicles,lithium-ion batteries determine the overall performance of new energy vehicles.During the normal operation of the vehicle,the lithium-ion battery will release a lot of heat and cause the temperature to rise.However,the lithium-ion battery is very sensitive to the temperature.If it is not controlled,it will affect the service life and safety of the battery.Therefore,It is necessary to study the thermal characteristics of lithium-ion batteries and develop a reasonable and effective thermal management system for lithium-ion batteries.In this paper,according to a brand of square soft-coated lithium iron phosphate battery,the temperature variation of single lithium-ion battery at different temperature and discharge current,and the temperature distribution of battery pack under different cooling modes are analyzed by experiment and simulation,and the temperature distribution of lithium-ion battery under different temperature and discharge current is analyzed by experiment and simulation.The specific contents and conclusions of the study are as follows:(1)The mechanism of heat generation in charge-discharge process of lithium-ion battery was analyzed,and the discharge experiments of single-cell battery under different discharge rates were carried out.The results showed that the discharge rate increased with the increasing of discharge time and the temperature of single-ion battery increased.The more heat generated,the more obvious the rising trend of temperature,and when the discharge rate reached 2C or even greater,the surface temperature of lithium battery increased almost linearly.(2)The heat conduction mechanism of lithium-ion battery is analyzed,and a suitable three-dimensional thermal model of lithium-ion battery is established.The temperature rise and temperature variation of single lithium ion battery under different temperature and discharge current were simulated and analyzed by obtaining the related thermal physical parameters and heat generation rate.The simulation results were compared with the experimental data.The accuracy of the three-dimensional thermal model established by simulation is verified.(3)With the increase of the channel width,the maximum temperature and temperature difference of the battery pack decrease with the increase of the channel width under air cooling alone,but the range of the decrease is smaller and smaller.The flow velocity of the double outlet scheme is obviously higher than that of the single outlet scheme,and the air flow flows along the nearest path from the outlet,and the high temperature distribution moves with the outlet position,and the moving direction points to the outlet position.(4)The cooling fin can not only improve the heat dissipation capacity of the battery pack,but also have a good effect on improving the maximum temperature difference of the battery pack.Under the combined cooling of air and cooling fin,the maximum temperature and temperature difference of the battery pack decrease slightly with the increase of the thickness of the cooling fin,but the effect is not obvious.With the increase of the extended length of the cooling fin,the heat dissipation ability of the battery pack is improved to a certain extent,especially when the 50mm is increased to 60mm,the heat dissipation ability is enhanced most obviously,and the degree of the improvement of the heat dissipation effect becomes weaker when the extension length of the cooling fin is continuously increased.