| Lithium-ion battery has been extensively used as power source for electric vehicles due to its high energy density,long cycle life and low self-discharge rate.However,temperature has a great influence on the performance and life of batteries or even leads to batteries thermal runway in extreme situations.Much attenti on has been paid to Lithium-ion battery thermal issues,which are highly related to the performance,lifetime and safety,and important factors in battery thermal management design.Therefore,it is necessary to understand the thermal behaviors of the cell during operating and design an efficient battery thermal management.In this work,lithium-ion battery thermal behaviors and thermal management system design are mainly concerned.Firstly,the Lithium-ion battery was investigated by the charge/discharge tests.Secondly,a multi-component thermal model was built and validated by experiments.Thirdly,the temperatures distributions of the battery pack at different charge/discharge rates were experimentally studied.Finally,a battery thermal management system with liquid cooling was proposed and analyzed by numerical simulations.(1)Temperature rise characteristics,voltage characteristics and capacity characteristics of the battery were analyzed by charging/discharging tests.Based on the charge test results,a stage division method of the temperature rise characteristics of the lithium ion battery during charging process is proposed,and the characteristics of each stage are summarized.In addition,a thermal imager was used to analyze the temperature distribution of the battery cell at different discharge rates and depth of discharge.On the basis of the experiment,a multi-component battery thermal model was established based on the structural features of the 18650 battery and the 1C,2C,and 3C rates discharge conditions were simulation analysis using the model.The simulation results of the battery temperature data and surface temperature distributions are in good agreement with the experimental data,indicating that the modeling can be used to analyze the thermal characteristics of the battery.(2)Thermal characteristics of the battery pack were analyzed by charging/discharging tests.The temperature characteristics of the battery pack and battery cell under 1C charging and 1C discharging conditions were compared and analyzed.Under the 1C charge condition,the maximum temperature of the battery cell is 35? and the maximum temperature of the battery pack is 45?.In the 1C discharge constant current condition,the maximum temperature of the battery cell is 36.6?,and the maximum temperature of the battery pack is 45.7?.For the charging and discharging conditions,the maximum temperatures of the battery pack are 10 ? and 9.1? higher than the battery cell respectively.The maximum temperature of the battery pack is much higher than that of the battery cell,which means that the heat dissipation performance of the battery pack is worse than that of the battery cell.To solve the problem of poor heat dissipation of the battery pack,a liquid-cooling battery thermal management system is designed.(3)The initial liquid cooling model was analyzed and optimized by numerical methods.The influences of different heat-conducting plate materials,coolant type,and coolant flow rate on the temperature field of the battery pack were analyzed.Aiming at the problem of non-uniform temperature distribution of the battery pack,optimization method for locally thickening the heat conducting plates was proposed,which effectively improves the temperature uniformity of the battery pack. |
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