Research On Battery Management System For Electric Vehicle

External dependency on energy more than50%and development under the background of low-carbon economy, the development of new energy vehicles is the trend of The Times. Power battery and its BMS (battery management system) is the core of new energy vehicles, that is the biggest bottleneck technology and cost. The Vehicle power supply system design is to control the technology, integrated electronic technology, process control for the integration of comprehensive high and new science and technology. Through years of development, our country and abroad in the battery performance gap is not big, but in the whole vehicle dynamic performance of power systems there is a big gap.The key technology of electric vehicle BMS is mainly including the charging technology, battery SOC (state of charge) estimation and equalization control, etc. Base on the pure electric vehicle of the lithium ion BMS as the research object, and study on these three aspects respectively.Charging technology determines the battery working time and service life, the longer charging time is the bottleneck of the popularization and application in the electric car. Firstly, the lithium ion batteries work principle and its performance is analyzed. And then the existing charging ways are introduced. At the end, according to Dr. Mas proposed the best charging electric current curve, this paper adopts the constant current-constant voltage (CC-CV) charge mode, and presents the different charging current and the cut-off conditions at various stages.SOC is one of the important parameters of battery management, is the direct reflection of battery capacity, on the hand, provide the driving range information to the driver, on the other hand, provide the basis for management and maintenance to BMS. At the beginning, the factors influencing the SOC are analysed and models of the battery are given. Based on them, Current integral method is combined with the Thevenin equivalent circuit model to establish a new state model of battery. Futhermore, some strategies of estimating the SOC are displayed and analysed, and the method based on Extended Kalman Filter (EKF) is researched. At the end, put forward a kind of hybrid estimate algorithm of SOC based on EKF-AH, and verifies its effect with experiments.Battery equalization control not only help to improve the use time of battery, you can also extend the service life of the battery. At the first, the dissertation also analyzes the significance and the reasons for disequalization, and introduces the current equalization control mode of different classification criteria. Secondly, discusses several existing balanced approach. At the end, put forward a2-level balance strategy. The experimental results indicate that the2-level balance strategy is superior to the first two balance methods in both balance speed and balance performance.At the end of the paper, introduces the design of lithium ion battery management system’s overall function, and each module’s hardware circuit design and software flow chart.