Thermal Performance Research On The Lithium-ion Batteries Of Electric Vehicle

Influenced by the oil crisis,the traditional fuel cars gradually replaced by the electric vehicles.As the preferred power source of the electric vehicles,the performance of the lithium-ion battery is seriously affected by the temperature.Ultra-high temperature can't make the internal heat of battery out in time,which even lead to adverse consequences such as fire and explosion.Ultra-low temperature can give a sharp drop in battery capacity,which reduce the working efficiency of the battery.Through battery thermal management system(BTMS),the battery problems of the ultra-high working temperature and the ultra-large temperature difference can be effectively solved,which has the great significance for improving the safety performance.The main research content of this thesis is as follows:(1)The calculation of parameter:The research methods of battery thermal management system by experts at home and abroad can be known.The heating characteristics and heat dissipation mechanism of the battery monomer can also be analyzed.At the same time the structure and working parameters required by simulation are computed,such as the average density,the average heat capacity,the average coefficient of thermal conductivity and the heat yield from battery ontology and ear(Copper pole ear,Aluminium pole ear)under different discharge rates.(2)The analysis of battery monomer:The influence of monomer battery temperature distribution among different discharge rate,different heat transfer coefficient and different environmental temperature is analyzed.Then summary and conclusion are completed.(3)The choice of the battery pack:The temperature between battery monomer and battery pack in the same conditions at the end of the discharge.The suitable arrangement of battery pack is selected and a cooling scheme is designed to get the simulation analysis.(4)The analysis of air cooling:The simple water cooling device is designed and the temperature distribution influence of the battery pack is compared between the natural cooling and air cooling.Under the condition of changing the discharge rate and ambient temperature,the influence of heat dissipation effect of air cooling is comparied by different inlet speed and the applicable conditions of water cooling device is summarized.(5)The analysis of water cooling:First the setting of the water-cooling device for battery pack and the confirmation of the inlet velocity are completed.Then the cooling effect among different discharge ratio and different environmental temperature by three ways including natural cooling,forced air cooling and water cooling is compared.Finally the above conclusions are synthesized to have applicable conditions of water cooling scheme.