| The energy crisis and environmental pollution which caused by fossil resources is always a hot issue for human society,and governments have focused on developing the new energy vehicle industry to alleviate this problem.Different from the traditional internal combustion engine,the new energy vehicles increasingly garnered support and acceptance owing to their advantages of easy maintenance,environmentally friendly,and reliability.But they also pose conspicuous challenges,such as mileage and the thermal safety of the battery pack,which is closely related to the research on battery thermal management system.In recently years,thermoelectric cooling/heating devices have been gradually used in battery thermal management research for their clean,quiet,and prompt response.In this paper,a battery thermal management system based on thermoelectric cooling/heating devices coupled with liquid cooling is designed.Besides,a test bench is built to study the thermal characteristics of the battery pack.The main contents and conclusions of this paper are exhibited as follows:(1)The thermal characteristics of a single lithium iron phosphate battery in thermoelectric cooling/heating system are measured,besides,its cooling performance is compared with natural convection cooling and liquid cooling which verify its feasibility.We find the battery thermal management system based on thermoelectric cooling/heating devices can quickly respond to battery demands for temperature.However,the significant decrease in the maximum temperature of the battery was accompanied by a bothersome increase in the temperature difference of the battery.(2)A simple module with four batteries in series is constructed to observe its cooling performance.We also assess the coolant flow rate,coolant temperature,the discharge rate of the battery pack and the condition with cyclic charge and discharge for the cooling effects on the battery pack.The results show that higher coolant flow rate and lower coolant temperature will lead to lower battery temperature.besides,even in the worst conditions,the maximum temperature of the battery pack can be kept below 41℃.(3)We respectively control the voltage(current)of each thermoelectric unit and explores the impact of the voltage(current)on cooling performance.When we set the condition as equivalent voltage,its cooling performance increases first and then decreases.Under the condition of differential voltage,the temperature difference of the battery pack has been effectively controlled.Piecewise voltage condition reduces the temperature fluctuation of the battery pack and maintains the balance between maximum temperature and temperature difference.Compared with the ambient temperature of 30℃,the maximum temperature of the battery pack only increases by1.2℃,and the temperature difference is not more than 5℃.(4)Changing the direction of current with DC power supply can realize the switch between thermoelectric cooling and thermoelectric heating.We find that the heating time of the battery pack can be significantly reduced when adding the voltage of the thermoelectric heating system.Meanwhile,it’s hard to absorb heat from the environment at low temperatures,the heat generated by the thermoelectric units is lost to the coolant,and the heat transferred to the battery is all from the joule heat of the thermoelectric units;Adding a thermoelectric heating fan on top of the battery can accelerate the preheating speed of the battery and reduce the temperature difference of the battery pack.When the voltage of the thermoelectric units at the bottom of the battery pack is 6V,the voltage of the thermoelectric unit and electronic fan at the top of the battery pack are 9V and 10 V respectively,the power consumption of the thermoelectric preheating system and the thermal characteristics of the battery pack can reach the optimal state,meanwhile,the temperature rise rate of the battery reaches0.64℃/min,and the total power consumption of the thermoelectric preheating system is only 86 W. |
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