| With the rapid development of global economy,the energy crisis and environmental pollution become more and more serious.It is an inevitable trend to develop new energy vehicles.With its high energy density and high output power,lithium-ion battery has become the first choice of battery pack for electric vehicles.However,the working temperature of Vehicle Lithium-ion battery pack should be between 25 °C and 40 °C,and the single temperature difference should be less than5 °C to ensure its good charging and discharging performance,life and safety,so a reasonable heat dissipation structure of battery pack is necessary.First of all,a set of battery characteristics test system is built to test the temperature rise characteristics of the battery at different discharge rate and the internal resistance characteristics of the battery at different temperature.The heat dissipation model of the cell is established by Icepak,and the temperature field distribution of the cell is simulated.Compared with the experimental results,the error is less than 5%,which proves that the cell model is basically reliable.After that,a 480 cell compact large battery pack with a total nominal voltage of72 V and a total nominal capacity of 69.6 Ah was designed.Under the condition of natural convection at 20 °C,the maximum temperature rise of the battery pack is22.48 °C and the maximum temperature difference is 8.78 °C when the battery is discharged at a rate of 1C.In order to reduce the temperature rise and temperature difference,an axial air cooling structure is designed to reduce the maximum temperature rise and temperature difference of the battery pack to 12.76 °C and6.44 °C.In order to further reduce the temperature difference,through the orthogonal test,a filter structure with different opening rate in different areas was designed,so that the maximum temperature difference of the battery pack decreased by 1.58 °C.In order to make the battery work in the appropriate temperature range under the bad condition of 40 °C and 2 C multiple discharge,the influence of air inlet speed and temperature on the temperature distribution of battery pack was studied.Two reasonable air supply strategies,30 °C,14 m/s,754.96 CFM and 29 °C,12 m/s and647.02 CFM,were developed.In order to reduce the required air volume,energy consumption and noise,the required air volume is further reduced to 596.4cfm by adjusting the air inlet hole diameter.Finally,in order to meet the layout needs of different models,a radial cooling structure was designed by orthogonal test.Under severe conditions,the maximum temperature rise of the battery pack is 2.68 °C and the maximum temperature difference is 8.9 °C when the air supply strategy of 12 m/s and 27 °C is adopted.In order to reduce the temperature rise and temperature difference,the form of reciprocating air supply is adopted,and the air supply strategy of changing the air supply direction every 60 s after 120 s and every 90 s after 120 s is formulated,which meets the heat dissipation requirements of the battery pack.Compared with the axial air supply structure,the required air volume is reduced by 291.3 CFM.In order to reduce the period of changing wind direction,the influence of wind speed on the strategy of reciprocating air supply is studied. |
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