Design Of Power Battery Management System For Electric Vehicle

With the rapid development of China's economy,the per capita vehicle ownership is increasing day by day,and the problems of energy consumption and atmosphere pollution have become increasingly prominent.To cope with the energy shortage and environmental pollution brought by traditional vehicles,new energy vehicles have emerged.However,new energy vehicles are still not mature enough in technology.As the key component of electric vehicles,the power battery and its management technology have become the key factors that restrict the development of electric vehicles.As the main energy source for electric vehicles,the performance and health status of the battery pack directly affect the vehicle's overall performance and running safety.Therefore,it is particularly important to monitor the power battery status in real-time and manage its charging or discharging.under the support of 2016 Liaoning province natural science funds project "research on key technologies of enrgy optimization and safty control for new energy vehicle based on mobile internet",the research on the power battery management technology of electric vehicles was conducted.By consulting a large number of literature about domestic and overseas power battery management technology,the mechanism and characteristics of the battery are studied,and the main technologies involved in the battery management system are analyzed.Among them,the estimation of SOC for power battery has always been a problem in battery management,its estimation accuracy influences the use of the battery and management of charging and discharging.For this purpose,the battery's SOC estimation methods are researched in depth,and through combining the open circuit voltage method with the ampere-hour integral method,the influence of temperature,charging and discharging efficiency,and other factors are taken into account,the ampere-hour integral method is modified and the SOC estimation method is simulated by building a simulation model.Then the overall design of the battery management system is proposed,the master-slave structure is used in the design of the system hardware architecture,the main control board circuit is based on the Freescale MC9S12XEQ512MAL microcontroller,and the minimum system circuit,power conversion circuit and current acquisition circuit are designed in detail.TI's battery management chip BQ76PL536A is selected as core of battery acquisition board circuit to achieve the voltage,temperature acquisition of single cell and balance of battery pack.SPI communication is used between the main control board and the battery acquisition board,a touch screen is adopted to display battery status information in real time,the communication method between the touch screen and the main control board is adopted RS-232 serial.In consideration of the electrical safety of the system,digital isolation devices are chosen to isolate the main control board from the acquisition board.In the aspect of software design,firstly the overall software design is based on system hardware circuit and battery management function requirements,secondly,based on CodeWarrior development environment,software flow of each functional module of the main control board and acquisition board are designed.The main control board software includes main program of the system acquisition,current acquisition subroutine,and SOC estimation subroutine.The acquisition board software design includes data acquisition subroutines,equalization control subroutine,and fault alarm subroutine,in addition,communication software are designed.At the end of the dissertation,the management function of the LiCoO battery pack is tested by building an experimental platform.Firstly,the acquisition functions of voltage,current,temperature of the system are tested.Nextly,the balanced control experiment and tests of SOC estimation on the battery pack are carried out.The experimental results show that the circuit design of the system is reasonable,and the functions of data collection,balance control and SOC estimation of the battery pack can be achieved,and the expected design goals are basically achieved.This research has practical significance for the promotion and application of new energy batteries.