Study On Low Temperature Preheating And Charging Performanceof Lithium Battery Of New Energy Automobile In High ColdRegion

The development of new energy vehicles has become a main direction for the development of the auto industry today,and also a major strategy for China to develop a low-carbon economy and meet emissions reduction.With the increased attention of new energy vehicles,the principal and local government have successively introduced a series of industrial policies to promote the development of new energy vehicles.The Li-ion batteries,which power the new energy vehicles,are influenced by temperature.When exposed to low temperature,the electrochemical reactions decrease and internal resistance increases on the battery.When the battery terminal voltage rises to the charging cut-off level,the battery capacity will be reduced and subsequently lower power can be discharged.As a result,the lithium battery life is significantly impacted.At low temperatures,the Li-ion batteries perform poorly.Li-ion batteries can scarcely be charged or discharged,and the overall performance in the low temperature environment will be negatively impacted.To improve the performance of Li-ion batteries and larger-scale applications in the alpine regions,the researchers from home and abroad have been studying on trending topics,including limits of low-temperature performance of Li-ion and the preheating feature of Li-ion batteries in cold climates.This paper summarizes the preliminary results of researches on charging/discharging performance at cold temperature,low-temperature preheating management system,low-temperature preheating scheme and Li-ion battery equivalent circuit model of electric vehicle lithium battery,applying the Whland multi-channel lithium performance measure system.The lithium battery static discharge capacity test studied the discharge capacity and discharging time of different lithium batteries under the impacts of various low-temperature environments.By employing the basic performance parameters of lithium battery to build the nonlinear model and the discharge curve of the nonlinear equivalent circuit model constructed in Matlab simulation,it aims to test the reliability of the model via the static discharge capacity test.A low-temperature preheating management system for lithium batteries was designed,and the idea of using PTC heating sheets to preheat lithium batteries was proposed.The specific conclusions can be summarized as follows:A multi-channel lithium battery charge and discharge performance test system has been established to study discharge characteristics of hosphoricacid iron lithium battery,polymer-lithium battery,ternary-lithium battery,and lithium-titanate battery in low temperature environment of 0,-5,-10,-15,-20,-25 °C.The results show that the constant current discharge time is proportional to the discharge capacity of lithium battery in low temperature environment.The low temperature environment has different effects on the discharge capacity and discharge time of different lithium batteries.The low temperature environment affects the discharge capacity of hosphoric-acid Iron lithium battery the most,followed by polymer-lithium battery and ternarylithium battery,and lithium-titanate battery the least.By establishing a nonlinear equivalent circuit model of lithium battery,it takes the performance parameter of 25 Ah lithium iron phosphate battery as the base model parameter and uses Matlab to simulate the discharge characteristics of the nonlinear equivalent circuit model of the lithium battery,and pass the static discharge capacity test of the lithium battery.The analysis results show that the hosphoric-acid iron lithium battery’s nonlinear modeling simulation discharge curve is consistent with the result from the static capacity,further proving that it can be used for the charging and discharging simulation experiment of the lithium battery.The PTC heating sheet is employed as the key pre-heating element to build the battery preheating management system,which mainly includes the main control module and the temperature acquisition module.Through the main control module,the power supply control of the battery pre-heating component can be achieved,the heating power of the lithium battery can be controlled in real time,and the battery surface temperature during the preheating can be collected in real time through the multi-channel temperature detection system.