Thermal Characteristic Research Of Battery Pack And Thermal Management System Development For Pure Electric Vehicle

With the growing energy crisis and environmental pollution, the development ofelectric vehicles has drawn increasing attention, the power battery is the only powerand energy of pure electric vehicles, and the performance and longevity of the powerbattery are influenced by the environmental temperature. Under the high temperatureenvironment,the irreversible reactants of the internal battery materials generate morequickly,the irreversible reactants lead to accelerating decrease for the availablecapacity, and the battery life ends when the battery’s available capacity attenuates to80%of the battery rated capacity; The internal resistance of the battery increases, thecharge and discharge voltage platform reduces，charge-discharge capacity decreases，charge and discharge efficiency of the battery is significantly reduced, and the batteryitself is damaged under the charge and discharge of the low temperature environment.Therefore,the thermal characteristic research of the battery pack and thermalmanagement system development for pure electric vehicles is of great significance.According to the LiFePO₄battery temperature characteristics and designrequirements of pure electric vehicle thermal management,this paper work as followsby using the LiFePO₄battery as the research object:（1）This paper accesses to a lot of information,analysises the research status ofthe battery thermal management, points out that the power battery and batterythermal management system problems, and chooses the reasonable cooling andheating structure.（2）This paper analysises the optimum working range for the battery by studyingits temperature characteristics;This paper drives the thermal battery parameters andheat rate formula from the battery heat, gets the battery specific heat capacity byprocessing the experimental data, and obtains the unit volume rate of the battery; Thispaper calculates the thermal direction conductivity of the equivalent battery materialbased on the thermal conductivity parameters of the battery materials, and verifys thethermal model by the temperature experiment.（3）Simulating the single battery by using the fluent software, the result isconsistent between the experimental and simulation,and shows that we can regard itas the single thermal model for the battery pack;It is necessary to design the coolingduct by establishing natural convection for the battery box model, analyzing the simulation results of the natural convection of the battery box, and pointing out itsproblems.（4）In order to improve the cooling effect of the battery box in the summer andthe battery performance in the winter,this paper does the following improvements forthe natural convection battery pack:（A）This paper increases in forced air-cooledmeasures by using the parallel ventilation.（B）The battery pack is heated in thebottom by using the heating film（.C）The battery pack increases the thermal insulationfunction. The side maximum temperature of the steady state for the battery is5degrees lower than the ambient temperature to meet the work requirements of thebattery by using CFD to simulate the cooling system of high-temperatureconditions;This paper chooses the way of lower temperature heating for a higherheating effect through the simulation of the upper and lower heating way andinsulation performance.This paper chooses the battery pack equipment and designsthe battery pack structure by obtaining the parameters with the remote monitoringsystem.（5）This paper make the rechargeable heating control strategy and cooling controlstrategy, designs and debugs the hardware and software for the thermal managementsystem.This paper verifys the function including the cooling system, heating systemand control strategy.