| The energy and environmental crisis is becoming more and more serious.The continuous development of the automobile industry consumes huge energy and brings serious environmental pollution.Governments and automobile companies of various countries have begun to turn their attention to new energy vehicles,such as pure electric vehicles.Ushered in new development opportunities.Power batteries are the main source of power for electric vehicles,and their performance directly determines the power,economy,and safety of electric vehicles.The breakthrough of key technologies for power batteries is an important condition for the marketization and popularization of electric vehicles.Among them,lithium-ion power batteries are quickly favored by the market due to their high energy density,long cycle life,low self-discharge rate,and no memory effect.However,the lithium ion battery will generate a lot of heat due to the internal chemical reaction during the working process.In addition,the battery pack is a closed space,and the heat is not easily lost.If the battery temperature is maintained at a relatively high range,the battery will be charged and discharged.There is a lot of damage in terms of efficiency,power output,and battery life.If the temperature continues to rise,it may cause thermal runaway of the battery,further jeopardizing the safety of electric vehicles.In addition,the accumulation of heat generated by each cell and the difference in transfer conditions will cause the temperature difference between the battery modules to become larger,resulting in inconsistency in the overall battery pack,which in turn will cause different internal attenuation rates of the battery pack,and the battery pack capacity utilization rate will decrease Affect the normal operation of the power battery.Therefore,the development of reasonable and efficient power battery thermal management technology is of great significance for ensuring the normal use of power batteries and extending battery cycle life.Based on the study of the working principle and thermal characteristics of lithium-ion power batteries,this paper explores the heat dissipation effect of the power battery thermal management system under different conditions through a combination of experiments and simulations,and analyzes the group structure and heat The management system layout method and the influence of the thermal management system related parameters on the maximum temperature rise and temperature distribution inside the battery pack provide guidance for the improvement and optimization of the power battery pack thermal management system.The main work and conclusions of this article are as follows:(1)By consulting the literature,comparing the advantages and disadvantages of various types of power batteries,analyzing the influence of temperature on the performance of power batteries,reviewing the research status of power battery thermal management technology at home and abroad,and listing several power battery thermal management systems Real vehicle application program;(2)Introduced the basic structure and internal electrochemical reaction principle of lithium-ion batteries,studied the heat generation characteristics and heat transfer characteristics of lithium-ion batteries;and obtained the lithium-ion power batteries under different SOC states through the experiment of battery internal resistance characteristics During the constant current charging and discharging process,the DC internal resistance of the battery changes.The results show that: when the battery SOC value is above 0.3,the battery internal resistance is basically unchanged;when the battery SOC drops below 0.3,the battery internal resistance will There was a surge;(3)For the lithium-ion power battery pack of the existing project,the effects of the liquid cooling plate layout of the thermal management system with liquid as the medium and the temperature of the cooling liquid on the heat dissipation effect of the battery pack are analyzed through experiments.The study found that after adding a liquid cooling plate at the bottom of the battery module,the overall maximum temperature of the battery pack dropped from 47? to 41?,and as the ambient temperature further increased,the decrease in the maximum temperature rise of the battery pack was further expanded;cooling was reduced The liquid temperature also has a significant effect on controlling the maximum temperature of the battery pack,but after the cooling liquid temperature is reduced to a certain limit,its influence on the battery heat dissipation is relatively weakened,and even the overall temperature uniformity of the battery pack will be reduced;(4)In view of the inadequacy of the experiment that the temperature distribution inside the battery module cannot be obtained accurately,the thermal simulation model of the power battery pack was established using relevant software,and the validity of the model was verified by comparing the simulation results with the experimental data under the same working conditions.Taking the ambient temperature of 25?,coolant temperature of 25?,coolant flow rate of 3L/min,and constant rate discharge of the battery pack as examples,the temperature distribution inside the lithium-ion battery pack was investigated.The study found that after discharge,the overall temperature distribution inside the battery pack is uneven,and there are certain temperature differences between the battery module along the liquid-cooled plate and the upper and lower surfaces,which needs to be optimized;(5)Taking the 2 parallel and 5 string modules with the largest heat generation in the battery pack as the research object,through experimental comparison methods,several methods to enhance the heat exchange effect between the battery module and the liquid cooling plate were studied to improve the battery module The effect of large temperature difference between the upper and lower surfaces and poor contact with the liquid cooling plate.The results show that: improving the heat transfer efficiency at the bottom of the module does not have much impact on the temperature rise of the top and side of the battery module.On the contrary,the temperature difference between the upper and lower surfaces of the module is further increased due to the lower temperature of the module;After placing the module on the side so that each cell contacts the same area of the liquid cooling plate,the temperature difference between the upper and lower surfaces of the power battery module is significantly reduced,and the overall temperature rise is also reduced.The effect is ideal. |
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