Thermal Analysis And Temperature Control Of Lithium-ion Power Battery For Pure Electric Vehicles

With the progress of science and technology,the electric vehicle industry in China has also entered a period of vigorous development,not only solving one of the technical problems after another,but also overcoming a series of technical difficulties,achieving support of the National Research and Development 863 Program is a very important reason.Many technologies have matured and reached the stage of mass production and sales.In some areas has developed with other countries in Europe and the United States,has even surpassed these countries.In some areas it has reached the progress of other European and American countries,even over these countries.Many domestic automobile enterprises,such as BYD,Changan,Jianghuai and so on,giving a strong support of capital and technology to new energy vehicles,especially electric vehicles.The state finance and related departments on the development of electric vehicles to give financial support and policy support,but from the current development of pure electric vehicles,there is still a lot of problems,one of the biggest problems is that many electric vehicles above not equipped with a perfect and comprehensive battery thermal management system,and many car manufacturers have not developed such a system.Under such circumstances,the research and development of battery thermal management system needs more attention,and it will also become the research focus of relevant research institutions and automobile manufacturers.The battery is the only source of pure electric vehicles provided above the driving force and related parts,only equipped with a perfect battery thermal management system for vehicle battery management,in order to make the temperature of the battery work in a reasonable range,to ensure the best electrochemical properties of the battery,thereby prolonging the service life of the battery.In this paper,the temperature field simulation of battery and battery pack is carried out first,then the heat dissipation simulation of the battery pack is carried out,and the temperature control of the battery pack is finally controlled by voltage balance.The main contents of this paper are as follows:1.The heat generation mechanism and heat transfer characteristics of lithium ion batteries are analyzed.First,the structure and working principle of lithium ion battery are analyzed.Then the mechanism of heat generation and heat transfer characteristics of lithium ion battery are analyzed,and some theoretical guidance for the establishment and Simulation of the thermal effect model is made.2.The simulation and analysis of the heat generation temperature field temperature field of the lithium ion battery monomer and the battery pack.First of all,the thermal effect model of lithium ion battery is established.Then,the thermal properties of lithium ion batteries are calculated,and the initial conditions and boundary conditions of the thermal effect model are determined.Finally,the geometric model of the lithium ion battery and the division of the grid are carried out,and the thermal field of the battery is simulated and analyzed.3.The simulation and analysis of the heat dissipation temperature field of the lithium ion battery group.First,the advantages and disadvantages of the three cooling methods are compared,and air cooling is selected as the heat dissipation mode of this simulation.Secondly,a fluid solid coupling model for the heat dissipation of the battery pack is established.The turbulent form is determined by the comparison of the calculated Reynolds number with the critical Reynolds number.Then,the coupling model of reasonable boundary conditions is set up.The simulation analysis of the heat dissipation temperature field of the battery group under 100 A constant current discharge and air inlet velocity of 2m/s and 5m/s,respectively,is carried out.Finally,the inlet and outlet have been improved through the analysis of the serial ventilation form and parallel ventilation mode,the simulation analysis of the heat dissipation temperature field of the battery pack is carried out again.4.The balance control of a single battery and a battery pack voltage.Firstly,the equilibrium control strategy is analyzed,and the equilibrium threshold is set up 0.15 and 0.1.Secondly,the design of balance mode is determined through the theoretical analysis of active equilibrium and passive equilibrium,that is,the resistance consuming passive equalization between battery packs and inductor active equalization between cell monomers.Thirdly,the structure design of the equilibrium system is carried out.At last,experiments on the static,charging,and discharge of cell monomer and battery pack by selecting the appropriate component.The experimental results verify the effectiveness of the design.