Research Of Lithium Ion Battery Health Evaluation Index On Electric Vehicle

In recent years, due to the increasingly serious energy crisis and environment pollution problem, the development of the lithium battery is attached great importance by governments. The lithium battery is recognized as the ideal energy by the current social, it’s used in all aspects of society. One of its important applications is that, the lithium battery is used as a very promising power source for pure electric vehicle (PEV). The battery performance directly affect the performance of pure electric vehicle. In order to meet the national requirements of electric vehicle, and ensure safe and reliable driving of the pure electric vehicles, Proper evaluation of the characteristic of power battery must be finished. With more and more researches on the battery, lithium battery health has become a key factor to evaluate battery characteristics. Therefore, the resistance model of lithium battery is set up according to its characteristics,and by means of the model, appropriate evaluation on the health of the battery is finished.Nowadays, the battery health assessment is generally based on external factors measurement of the battery. Evaluating effectiveness is just passable, and predictive effect of battery life is also modest. In this paper, establishing the battery model, the internal parameters of the battery is obtained through system identification, and then to analyze the internal parameters of the battery according to the external characteristics, this paper Put forward a new method for assessment of battery health. The internal parameters of battery, such as resistance,to estimate the health of battery, which can effectively solve the shortcomings of traditional methods and provide a guidance for predicting the life of battery on Engineering.This thesis mainly has done research work as follow:Firstly, this thesis sets up the battery internal resistance model, and writes its transfer function. Then use the recursive least square algorithm to identify each parameter of the battery, and establish the cell model in Simulink, verify the feasibility of the battery model.Secondly, in order to find out the factors affecting the battery health, such as temperature, cycle times, charge and discharge current, discharge cut-off voltage etc, charge and discharge experiment on automotive lithium battery has been done.Thirdly, this thesis figures out the inside parameters of the batteries under different use conditions by method of system identification technology. This thesis analysis the reasons of effect state of health. And Gives a reasonable indicator for assess battery of health.