Research And Design Of Management System Of EV Lithium-ion Batteries

With the energy shortage and environment pollution becoming increasinglyserious, many countries around the word strengthen the research on electric automobile.As an important part of electric automobile, battery management system (BMS)realizes real-time monitoring and management for battery in entire process. Mainfunctions of BMS include the security protection, battery charged state (State ofCharge, SOC) estimation, the equilibrium between batteries and the battery faultdiagnosis, etc. BMS ensures battery could work safely and avoids damage caused byabuse, so as to prolong the battery life. Therefore, the research of BMS has importantpractical significance on electric vehicle promotion.Based on the analysis of the BMS research status at home and abroad this papermainly research and realize the BMS. In this paper, the main contents are as follows:First, on the basis of understanding of the lithium battery this paper analyses thecharacteristic of current battery models. Then choose the second order RC equivalentcircuit model as lithium battery model and put forward online identification methodthrough using up recursive least square algoritm of gradual failure memory to realizemodel parameters, which is based on off-line identifying model parameters by pulseexperiment. Second, paper analyses the advantages and disadvantages of current SOCalgorithm, and discuss the feasibility of the extended kalman filtering technologyapplication in the SOC algorithm. The paper puts forward a hybrid estimationalgorithm according to the EKF method, the Ah method and the open circuit method.Third, based on the analysis the causes and harm of battery imbalance, the paperaccording to the problems of current equalization scheme in effect, practicalapplicability, etc, presents a strategy of active equilibrium control, and gives theexperiment verifying results of the scheme. Fourth, the paper puts forward a scheme ofBMS overall function design, and according to the scheme completes the design andrealization of hardware system and software system. The hardware system gives theworking principle and circuit principle diagram of hardware function modules. Moreover, the software system gives function information and logical flow chart ofsoftware program.Up to now, the BMS is completed, and the test result shows that the designedBMS fulfill the requirements.