SOC Estimation And Monitoring For Lithium-Ion Batteries

n recent years,the total amount of cars has increased dramatically,and it is expected to grow by 7% in the next few years.The emission of CO2 will increase sharply and the environment will be extremely polluted.This has led to an increasing number of countries promoting new energy vehicles and gradually replacing chemical energy with electricity.Because of its advantages such as high energy and long charge and discharge life,lithium battery has become the ideal power source for new energy vehicles.The State of Charge represents the residual capacity of the battery,which is the key problem in the research of battery management system.In this paper,lithium ion battery is used as the research object,and the estimation and monitoring of the SOC of lithium battery is focused.In this paper,the research significance of lithium battery and the research status at home and abroad are discussed in this paper,which lays a foundation for the research of lithium battery.Secondly from the internal structure of lithium ion battery,this paper introduces the working principle of lithium-ion batteries,and factor of influence on the properties of lithium batteries(such as temperature,charge and discharge rate,voltage,etc.)are simply analyzed.In this paper,the Thevenin model of lithium battery is selected by analyzing the common equivalent circuit models of lithium batteries.Based on the periodic pulse test data,the relationship between OCV-SOC of lithium battery was fitted by the sixth order polynomial.The parameters of Thevenin model are identified based on least square method.Then,based on the established lithium battery model,an extended kalman filter was used to estimate the SOC of the lithium battery in the periodic pulse condition,the constant current charging condition and the constant exhalation condition.The simulation results show that it is feasible to estimate the SOC of lithium battery based on extended kalman filter,and the simulation results are good.In order to protect the battery,prevent the lithium battery overcharge,discharge and temperature,extend battery life,this article USES STM32 and DS2438 battery monitoring chip design with a lithium battery status monitoring system,and the monitoring system of hardware and software design in detail is introduced.The designed monitoring system can monitor and display the working voltage,current and temperature of the lithium battery in real time.When the lithium battery works abnormal,the system can alarm in time to protect the battery.