Study On Thermal Management Of Power Battery Under The Influence Of Busbar Heat Generation

As the core component of pure electric vehicle,the safety of power battery has always been the focus of attention.The factors affecting the safety of power battery include low temperature,high temperature,impact,aging and so on.At present,the temperature of lithium ion cell widely used in power battery and its internal temperature balance have a great impact on its life and performance,so it is necessary to use thermal management technology to make the cell work in the appropriate temperature range.As the market for electric vehicle range and dynamic requirements gradually increase and the monomer battery technologies are difficult to meet these requirements,more and more professionals choose to adopt a larger capacity batteries and more series-parallel module to meet the demand,in the form of larger capacity batteries and more serial-to-parallel module means need to carry more current busbar,The joule heat generated by these bus bars will inevitably have a certain impact on the temperature of the cell itself and the ambient temperature.Therefore,it is of great significance to study the relevant thermal management of the bus bars inside the power battery.On the one hand,it can explore the influence of the heat generated by the bus bars on the temperature field of the cell.On the other hand,it can guide the improvement design of thermal management system according to the research results.In this paper,a square lithium iron phosphate cell is taken as the research object,and a numerical calculation model of heat generation and heat transfer of the cell is established by exploring its internal working principle and heat generation and heat transfer mechanism.Then relevant experiments were designed to obtain the external circuit parameters of the cell,and the heat generation rate in the heat generation model was fitted with the experimental data.Then,CFD simulation tool was used to establish a THREE-DIMENSIONAL thermal simulation model,and the temperature rise data of the cell under different working conditions were obtained by designing experiments to verify the accuracy of the simulation model.In the process,a convective heat transfer coefficient correction method based on experimental data was proposed to correct the thermal model of the cell.On the basis of the mathematical model for heat batteries,combined with the bus-bar heat production model to carry out the module level temperature characteristic research,respectively discusses the different working conditions with and without considering bus-bar producing thermal cases module of temperature field distribution characteristics,analyzes the bus-bar is produced under different working conditions of thermal power battery module,the influence of the temperature field distribution,the results pointed out that in large capacity batteries group of power battery,The joule heat on the busbar at high rate conditions has a great influence on the distribution of the module temperature field,which should be taken into account by practitioners at the beginning of thermal management design.The cooling effect of the traditional cooling system under the influence of the heat produced by the busbar is analyzed.The results show that the traditional cooling system cannot effectively improve the temperature rise on the top of the module and the busbar under the condition of large discharge rate.It is found in the study that changing the layout of cooling plate and the shape of cooling pipe can greatly improve the distribution balance of temperature field and cooling effect of cooling system.Therefore,the layout of cooling plate and the shape of cooling pipe are optimized.The results show that the optimized cooling system can effectively improve the temperature rise of the bus bar and the top of the module while ensuring the overall cooling effect of the cell.Finally based on the original cooling fluid temperature solidification problem easily,for the research of the factors affecting the cooling effect of cooling system,by studying the different cooling plate thickness,cooling fluid volume concentration and the coolant inlet flow’s influence on the cooling effect to further optimize the cooling system related design parameters,the final design parameters combination can satisfy the cooling effect of the cooling system,It can improve the problem that the original coolant is easy to solidify at low temperature.