Dissertation
Dissertation > Transportation > Road transport > Automotive Engineering > A variety of automotive > Various energy vehicles > Electric vehicles

Study on Thermal Effects of Lithium-ion Battery in Electric Vehicle and Battery Package Dissipation Structural Optimization

Author LiTao
Tutor HuJianJun
School Chongqing University
Course Vehicle Engineering
Keywords Electric Vehicle Lithium-ion battery Temperature field CFD Experimental
CLC U469.72
Type Master's thesis
Year 2013
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Electric vehicles is simple in structure, easy maintenance, good operatingperformance, compared with the traditional fuel vehicles with no vibration, no noise, nopollution emissions, and broad development prospects, has become one of the importantdevelopment direction of the automotive industry in the future. As the only energystorage components, power batteries for electric vehicles will directly affect the vehicleperformance. With high voltage platform, energy density, high power density, long cyclelife, low self-discharge rate, less pollution, etc., the lithium-ion battery become thepreferred choice for electric vehicles.Along with the charge and discharge, lithium-ion battery pack will generate a lot ofheat in the normal operation of the electric vehicle, the internal temperature of thebattery pack will be rising and the distribution of temperature is not uniform if the heatcannot be dissipated in time, which reduces the performance of the battery, even cyclelife and safety. So, in order to guarantee the stability of the battery performance, it isnecessary to make the working temperature of battery pack maintain under suitablecritical temperature, also to control the internal temperature difference within a certainrange. Therefore, establish a thermal analysis model of the battery, use numericalsimulation techniques to simulate temperature distribution of the cell and battery packunder different conditions, predict the thermal performance of the battery pack andoptimize the heat dissipation structure, which has important practical significance togive full play to the battery performance. In this paper, experimental verification andCFD technology combined to analysis the temperature rise of the lithium-ion underdifferent conditions, then simulated the dynamic performance ofbattery pack based onthe different driving cycles, modeled and numerical computed the temperature field oflithium-ion battery pack, finally, put forward improvements to make the heat flow andtemperature distribution of battery pack uniform.The research work of article has the following aspects:①Analysised the temperature rise of the lithium-ion cell by experiment under thedifferent charge-discharge rate, the change of resistance and the open circuit voltagewere tested during charging and discharging process at different temperatures;②Analysised the generate heat mechanism and heat transfer characteristics of thelithium-ion battery, lithium-ion battery thermal model was established according to the heat transfer theory, and the cell was simulated;③The simulation model of lithium-ion battery pack was established with thesoftware ADVISOR to simulate and analyze the dynamic characteristics under differentcyclic conditions, and obtained real-time heat rate and changes in the amount of heatused the model.④Using CFD technology, the flow field and temperature field of electric vehicleslithium-ion pack original heat dissipation structure were simulated and analysised. Toverify the accuracy of the temperature field model and the simulation results, thelithium-ion battery pack on-site experimental measurement was carried out, andexperimental results and simulation results are in good agreement. Finally, theimprovement programs to optimize the flow and temperature field distribution oflithium-ion pack cooling system were proposed.

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