Research On Battery Management System For Light Electric Vehicle

In recent years, with the establishment of new energy strategy and the continuous input from more and more companies, the development of electric vehicle become easier and better. Low or even zero emissions, high energy using efficiency, low noise are all the advantages of electric vehicle. Light (low speed) electric vehicle is forming a industrialization in china because of its cheap price, low cost of maintaining, easy to use. Estimating the state of charge validly, avoiding over charge and discharge, improving the battery using efficiency, and extending battery life are key technologies that must be solved in the process of industrializationBattery management system can detect the voltage, current, temperature of batteries real-time by sensors, with the corresponding algorithm and control strategy to achieve the above functions. With the support of the national natural science foundation, the paper developed a battery management system for light electric vehicle. It mainly includes three functional modules:battery protection module, data acquisition and processing module, battery equalization management module. In order to realize the functions of the battery management system, the paper will research the following aspects:performance and protection system research of lithium-ion battery, data acquisition system and SOC estimation method research, management strategy and simulation analysis of the battery equalization, the realization of the battery equalization system.Doing Lithium-ion battery charge and discharge experiments with different charge-discharge rate (0.5C,1C,2C,3C), the changes of the Lithium-ion battery performance parameters under different charge-discharge rate is been summed up according to the experimental results. It provides a foundation of the Lithium-ion battery protection and SOC estimation. The battery protection module is realized by the special protection chip, and can cut off the power supply circuit when the battery is in the extreme conditions.The research of data acquisition and processing module mainly contains the following parts:battery voltage, current, temperature and other parameters acquisition, the relationship between SOC and battery external parameters (voltage, current, temperature etc.), research on high-precision effective SOC estimation methods and realize the SOC estimation. To facilitate data processing, the system contains data storage module which is based on the USB interface and supports multiple types of external memory.The battery equalization management module adopts lossless active equalization manner with switch topology structure to compose a dynamic power transfer loop, transfers energy between different batteries by energy storage devices. The cell with higher voltage will charge the one with lower voltage, the higher voltage cells and the lower voltage cells will be all equaled at the same time in this way.Through the experiment on electric vehicle test bench, the battery management system can detect and store parameters of the battery pack real-time, display the parameters on touch screen, estimate the SOC, equal cells’voltage in the battery pack, and reduce the voltage inconsistency between cells.