Design And Implement Of Battery Management System And BMS Testing System For An Electric Vehicle

With the energy and environmental issues become more and more serious, new energy vehicles are holding more people's attentions. Power battery is the core component that determines the performance of the electric vehicle.Battery management system communicate with the vehicle controller and charger,protect charge and discharge process of the power battery,balance the cell batteries,estimate the state of charge according to some algorithm and provide mileage information for the driver.Vehicle manufacturers and battery manufacturers need BMS testing devices to verify and access the BMS product.But the BMS technology is not yet fully mature and there is not a industry standard for the BMS testing and verification.This paper first analyzes the main functions of the battery management system.The main functions of the BMS are to measure the state parameters of the batteries,protect the charge and discharge process,provide thermal management for the batteries,estimate the state of charge of the battery,balance the cells and communicate with vehicle controller and charger.In this paper,the parameter identification method of Thevenin model for lithium battery is studied and the open circuit voltage method,current integral method and the extended Calman Filter are conbined to estimate the SOC of lithium battery.On these basises,a BMS product is designed and implemented for a hybrid bus.This BMS product adopt the master-slave structure.The master module implement the functions of pack voltage measurement,pack current measurement,SOC estimation,insulation detection and communication.The slave module implement the functions of cell voltage measurement,battery temperature measurement and balance etc.In order to detect the function and precision of BMS product and select suitable BMS for battery pack,an innovative design of BMS testing and verification system is carried out.The overall scheme and design principle of the system are explained in this paper.The output precision of this system is test in detail and the results shows that the system has good accuracy and it can be applied to the testing and verification of BMS product.