| The long-term solution of energy consumption and environmental pollution is to develop electric vehicles. But the battery technology is the major factor that restricts the development of EVs. The temperature which the NCM battery shows the best performance is between 15℃ and 35℃. Lithium-ion battery’s performance is sensitive to the environmental temperature. For example, performances such as the charge-discharge voltage and the internal resistance will drop sharply when the temperature is below 0℃, which even causes the invalidation. To ensure the Lithium-ion battery working healthy, this paper has done some works about the thermal management system at low temperature.The charging and discharging tests of Lithium-ion battery with different rates and various environmental temperatures are conducted. The battery’s characteristics, which are temperature rising capability, discharging voltage, charge-discharge capacitance, internal resistance and so on, are analyzed. The results show that the low temperature effects the battery performance significantly and become the research basis of the thermal management system at low temperature.According to the mathematical model of heat transfer and the thermal parameters of Lithium-ion battery, the finite element model of the battery is built in ANSYS software. The simulation result of the cell model is minor different with the test, which satisfies the precision requirement. The temperature field effected by discharge rates and coefficients of heat transfer are discussed based on the simulation.The insulation structure of the Lithium-ion battery box is designed. The simulation model is verified by the experiment. The heat insulation effects which are related to the thickness of insulation layer, the thermal insulation material and the coefficient of hear transfer are simulated. Moreover, this design’s performance is tested in different temperatures. The result shows that the silica aerogel sheet with the thickness less than 10 mm can meet the insulation requirement at the critical low temperature of-30℃.The heating system of the box is designed. The heating time and the energy consumption of this heating method are better than the common methods, which is shown by the simulation. Meanwhile, the heating effects which are related by the power of electrical heating films, the location of those films and environmental temperature are analyzed. The heating model is verified the effectiveness by the test. The test results also discuss the operational safety of electrical heating films and the recovery property after being heated by this heating method. Finally, a strategy of heating control based on the heating time and the uniformity of heating temperature is proposed. |
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