| Battery technology is the key technology to restrict the development of electric vehicles.Compared to the traditional lead-acid battery and Ni MH battery, lithium ion battery got a large favor of electric car manufacturers because of the high specific energy, high monomer voltage, long cycle life and no pollution,which is currently the most value of the battery.Battery thermal management directly affect the battery cycle life and operational efficiency,especially in high temperature or fast charge discharge cycle with high current, which will cause severe chemical reactions inside the cell, release thermal reaction greatly and bring unpredictable security risks. In general, the optimum operating temperature range of the lithium ion battery is 25 ? -40 ?. The maximum temperature is not more than 45 ? and the temperature difference between the battery modules is less than 5 ?.Therefore, in order to solve the battery overtemperature and temperature non-uniformity problem, preliminary experiment research and numerical simulation have been carried on the heat dissipation performance of lithium-ion battery mudule under large discharge ratio, by using the heat pipe cooling technique and supplementing by way of air cooling. In this paper, the main research work are listed as following:(1) Through the Neware battery charge and discharge platform, the temperature rise features of the 18650 cylindrical lithium-ion battery during charging and discharging process has been experimented, obtaining temperature characteristics of he lithium-ion battery under different charging and discharging rate and resistance characteristics under different ambient temperature as well as the temperature distribution of the monomer battery under different positions,and obtain the thermal physical parameters of lithium-ion and heating rate on the basis of experiment.(2) The three-dimensional lithium ion battery thermal simulation model is established and transient numerical simulation of the monomer battery was done with different discharge current, which obtained the lithium battery temperature distribution deadline of discharge.Meanwhile, comparing simulation results with the experimental data has found that the simulation results of temperature curve and experiment of measuring temperature curve has a good consistency.(3) Under the condition of natural cooling, battery pack's heat dissipation was explored under the different arrangement of battery pack, which found that the overall battery cooling effect with fork row is better than in-line structure, mainly manifested in its good temperature uniformity, but it is difficult to meet the cooling requirement of battery overtemperature.Under the condition of forced air cooling,cooling temperature field distribution was studied under four different ventilation pattern. By compared the temperature distribution of battery pack and battery box center, optimal ventilation mode was got. On this basis, the effects of the battery heat dissipation under different wind speed has been furtherly studied.(4) Heat dissipation module of air cooling - heat pipe type is established by applying heat pipe and fin to lithium battery cooling system, and numerical simulating on heat dissipation performance of air cooling-heat pipe type was done. Firstly the paper studied the structural parameters of the fin, mainly including the fin spacing and thickness, which got the optimal layout structure.Then compared with heat dissipation way of forced air cooling,battery pack's temperature distribution of of air cooling-heat pipe type was studied, which mainly analyzes the internal temperature field of the lithium-ion battery pack at the different discharge, different environment temperature and the different speed of inlet wind. Analysis results show that the heat dissipation module can control the highest temperature of battery pack under 45?, at the same time guarantee the battery temperature uniformity, which maens the temperature difference can be controlled under 5?. |
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