Research On Improved Three-stage Charging Technology Of Lithium Battery

This paper expounds the importance of rapid charging of electric vehicles,explains the current research status of existing charging methods,summarizes the advantages and disadvantages of the present charging methods,and analyzes the existing el ectrochemical model,neural network model and equivalent model of batteries.According to the characteristics of lithium battery,the complexity and accuracy of the model,this paper chooses Thevenin model as the main research object.Firstly,the Hybrid P ulse Power Characteristic(HPPC)experiment is conducted on lithium batteries in this paper,and various parameters of Thevenin model are identified,and then curve fitting is carried out with them.After MATLAB fitting,the functional relationship between open circuit voltage,DC internal resistance,polarization internal resistance and State of Charge(SOC)is obtained,and then the Thevenin battery model is established by using Simscap physical modeling platform in MATLAB software.The constant current d ischarge simulation of the established model is carried out,and the output voltage of the model is compared with the actual measured voltage.If the errors are within the allowable range,the model is considered to meet the requirements.After the battery modeling identification,this paper analyzes and verifies the improved three-stage battery charging method.Based on Maas charging theory,this paper introduces the effect of battery polarization on battery performance,and analyzes the method of depolarization effect.Traditional three-stage charging method cannot have satisfied demand for lithium battery charging speed,so this paper presents a modified three-stage charging method,and utilizes Simulink platform to simulate,the results show that the modified three-stage charging method than the traditional three stage charging method is shorter,which provides a theoretical basis to establish a charging system based on the STM32.Moreover,this paper builds a charging system based on STM32 and adopts fuzzy PID algorithm to control charging current in real time,which improves the traditional three-stage charging method.Based on the analysis of experimental test and data,the improved three-stage charging method proposed in this paper is further verified to shorten the charging time and prove the feasibility of the system scheme.There are 67 graphs,12 tables and 56 references in this paper.