Thermal Models Of Cylindrical Lithium-ion Battery For Electric Vehicles

With the energy crisis and environmental pollution problems, the development of electric vehicle has gradually at tracted more and more attention and the performance and service life of the battery become key factors in hindering the development of electric vehicle. The battery temperature will cause irreversible reaction increased and reduce battery available capacity to shorten t he service life of the battery. Low battery temperature will increase the resistance and reduce the battery charging and discharging efficiency. Therefore the battery temperature need to be well predicted and monitored.This paper takes the electric automobile 18650 cylindrical lithium-ion battery as the research object. The main work content is as follows:(1) First by consulting lots of literatures on the battery thermal model the battery thermal characteristic research status is analysed. The existing problems and research trend are pointed out.(2) The structure and working mechanism of 18650 cylindrical lithium-ion battery are introduced and the battery heat generation mechanism is studied. By testing the battery performance the parameters of the equivalent circuit model are identified and validated by Simulink simulation. And the surface temperature of battery is measured by infrared imager.(3)By using the least square method the specific heat capacity and thermal conductivity are calculated through the battery surface temperature experiment. The battery thermophysical parameters are optimized by genetic algorithm.The results of the parameters are validated by Matlab simulation.(4)The 1D, 2D and thermoelectric coupling thermal model s are established through FLUENT software. The temperature field distribution is simulated and the surface temperature is compared with the experimental result. The result shows that the experimental temperature and the simulated temperature are basically the same. The reliability of the three thermal models are verified. The simulation results of the internal battery temperature by different thermal models are basically consistent. The internal temperature field distribution of single battery can be estimated in this way. The simulation effect of the thermoelectric coupling model is the best of the three models by online feedback of the temperature and SOC which will provide reference and guidance for the thermal management system.