| The power battery is the energy storage device and power source of the electric vehicle,and its performance is an important factor affecting the development of the electric vehicle.Since the temperature has a great influence on the charge and discharge capacity,cycle life and safety of the power battery,the thermal management of the battery pack with the battery operating temperature range and the internal temperature difference as the control targets has become an important research topic.In this paper,lithium ion battery is taken as the research object,and the battery discharge performance,cycle life and heat generation effect experiment were carried out to study the influence of temperature on the thermal characteristics of the battery.The battery heat generation and heat dissipation numerical model was established.Based on this model,an electric motor was used.The forklift carried out battery pack grouping and heat dissipation structure design,and carried out battery model CFD simulation.The main research work is as follows:(1)The 18650 lithium-ion battery was selected as the research object,and an experimental platform for battery cell heat generation was built.The experiment of battery thermal characteristics was carried out.The discharge performance test of the battery and the cycle life test of the battery were carried out respectively.The influence of temperature on the discharge capacity and cycle life of the power battery was obtained.The heat generation experiment of discharging the battery at different discharge rates under different ambient temperatures was carried out,and the curve of battery temperature with time was obtained,which provided data support for battery heat generation model verification.(2)Based on the Fluent simulation platform,the numerical model of single cell heat generation was established.The model was verified according to the experiment of battery heat generation characteristics.The verification mainly included the change of battery temperature value when the battery was discharged at different discharge rates under different ambient temperatures.It shows that with the increase of discharge rate at different ambient temperatures,the simulated and experimental temperature error values increase no more than 2 °C,and the two trends are consistent,so the model can be used for battery heat generation temperature field prediction.(3)The numerical model of heat dissipation of battery module was established.The temperature field of the battery module was analyzed by simulation at normaltemperature and fixed discharge rate.The contact and the non-contact temperature measurement points were taken out in the battery module.The comparison between simulated and experimental values shows that the model can be used for battery thermal management analysis.(4)Based on the power performance requirements and structural characteristics of the object electric forklift,the power battery group structure was designed,and three liquid cooling heat dissipation channels were proposed according to the battery pack discharged at different discharge rates at different ambient temperatures.The heat dissipation effect simulation was carried out to compare the maximum temperature and the maximum temperature difference of the battery pack,and finally the cold plate type serpentine structure was selected as the optimal heat dissipation structure.The variation of the battery pack temperature field of the battery module under different coolant inlet flow and coolant inlet temperature was simulated.The simulation results show that the designed heat dissipation structure is reasonable and meets the requirements of the operating temperature range and temperature difference design of the electric forklift battery module. |
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