Design Of Low-speed Electric Vehicle Battery Management System

Since the 21 st century,with the destruction of the ecosystem,the air pollution problem has become more and more serious.Automobile exhaust is one of the main factors of air pollution,so there is an increasing demand for the promotion of electric vehicles.Low-speed electric vehicles are widely used in the logistics and transportation tool market because of their low cost,lightness and simplicity.Although low-speed electric vehicles are less expensive to purchase,there are hidden dangers in their battery life and safety performance.In order to achieve safe and effective management of electric vehicle battery packs,the paper proposes a battery management system for low-speed vehicle battery packs.The system uses a modular design.Each module has its own independent power supply.The modules can work independently,which is convenient for debugging and Maintenance can greatly improve system reliability.The main work of the thesis is as follows:(1)The functional requirements of the power system of low-speed electric vehicles are analyzed,and the implementation scheme of the battery management system is designed.The system is divided into functional modules such as real-time monitoring,protection,energy management,and information management.The operating characteristics of the lithium-ion battery are analyzed,the battery dynamic model is established,and the extended Kalman filter algorithm is selected to estimate the state of charge(SOC)of the battery.(2)Each hardware module of the battery management system is designed,and the printed circuit board diagram is drawn.The system hardware scheme is divided into three hardware modules: main control board,acquisition board and protection board.The main control board circuit includes modules such as minimum system,power supply,sampling,display and communication.The protection board includes power and drive circuits and limit value hardware protection circuits.The acquisition board includes modules such as a single voltage sampling and equalization circuit,a temperature sampling circuit,and an on-board MCU circuit.CAN communication is used to exchange data between the acquisition board and the main control board.(3)In order to improve the accuracy of user electricity metering,the system adds a power metering function and uses a protection scheme combining software and hardware to improve system reliability.Module programs such as initialization,information sampling,SOC estimation,electricity metering,balancing,and protection are designed.The BMS system experimental prototype was built based on the total voltage of60V20 Ah lithium iron phosphate battery pack,and the system acquisition accuracy,SOC estimation effect,equalization effect and protection function were experimentally verified.The results show that the designed system current acquisition accuracy is high and can be The protection of the battery is realized from both software and hardware.The SOC estimation is relatively stable and the battery consistency is good,which verifies the reliability and stability of the battery management system.