State Evaluation And Key Technology Research Of Electric Vehicle Retired Power Battery

Focused on the lithium ion power battery of electric vehicles,firstly analyzes various power battery models,and selects RC equivalent circuit model according to the application characteristics of retired power battery step utilization,and obtains the corresponding parameters through the basic performance test of lithium battery.Secondly,in terms of the analysis of the performance parameter attenuation of the retired power battery,the evaluation method for the state of charge,health,function and safety of the retired power battery was proposed,and the test verification was carried out.Finally,the consistency of battery recombination is analyzed and the consistency screening method is given.A reasonable test system for evaluating the status of retired power batteries is developed based on a large number of retired power batteries,and an evaluation method for successive utilization of lithium batteries is formed.The main research contents are as follows:1.Based on the improved unscented Kalman filter algorithm and BP-EKF(Back Propagation-Extend Kalman Filtering)algorithm,the assessment of the charge state of retired lithium ion power battery was carried out.In order to improve the estimation accuracy of the kalman filter algorithm,a method of compensating and optimizing the Kalman filter algorithm through BP neural network algorithm is proposed in this paper.Firstly,the BP neural network is trained,and then the training results are verified to verify the accuracy improvement,convergence and robustness of the algorithm.2.Analysis of the capacity,open circuit voltage and internal resistance evaluation retired the effect of lithium ion power battery state of health,based on the lithium ion battery charge and discharge capacity and the anode and cathode embedded lithium ion ability,with battery aging degree increasing,the intercalated-li ability can reflect the change of state of health,so this paper proposes a combination of charging and discharging health health status evaluation methods.It is verified that the method can reflect the change of battery internal resistance and lithium embedding ability with the increase of cycle times.3.In view of the influence retired lithium ion power battery function of the state of the related parameters is uncertain,this paper proposes a functional state evaluation method based on fuzzy logic,the method will be charged capacity,internal resistance and charged retention rate as input,establish the membership function of fuzzy logic algorithm,and to validate the method,The results show that this method can not only show the use of retired power battery step utilization,but also reduce the recombination ratio,and improve the recombination efficiency.4.According to the test results of the basic parameters of lithium batteries and the evaluation results of the charged state,health state,functional state and safety state of lithium batteries,the retired batteries are sorted and reassembled to provide a basis for the subsequent cascade utilization.