Research On Residual Cpacity Estimation And Sorting Method Of Decommissioning Batteries Of Electric Vehicles

The performance of the retired batteries are discrete,When used in echelon,the remaining capacity of retired batteries need to be estimated,and the retired batteries also need to be resorted and reorganized.In order to realize the rapid and reasonable separation of retired batteries,the paper studied the estimation and separation method of the residual capacity of the retired batteries.The batteried are three element lithium battery with square shell retired from plug-in hybrid electric vehicle.Firstly,by analyzing the aging characteristics of lithium battery,it was found that the residual capacity,internal resistance and polarization characteristics are the important factors affecting the separation of retired batteries.By analyzing the process of charging and discharging,it was found that there is a long time consuming problem in the measurement of the remaining capacity of retired batteries.By analyzing the characteristics of internal resistance,polarization and capacity attenuation of retired batteries,it was found that for retired batteries with similar residual capacity,the difference of internal resistance and polarization characteristics will lead to the difference of capacity attenuation in the process of subsequent work.Secondly,taking the peak height,peak position and peak area as the characteristic parameters of the capacity increment curve of the constant-current charging stage.The changes of the characteristic parameters and the residual capacity of the decommissioning battery in the cycle behavior was analyzed.And it was found that the characteristic parameters of the capacity increment curve can reflect the residual capacity of the decommissioning batteries.On this basis,a method of estimating the residual capacity of retired battery based on capacity increment and Gaussian process regression was proposed.According to the correlation between the characteristic parameters of the capacity increment curve and the residual capacity of the retired batteries,the mapping relationship between the characteristic parameters of the capacity increment curve and the residual capacity after dimensionality reduction can be established by using the Gaussian process regression method,and the residual capacity of the retired batteries can be estimated rapidly.Then,taking ohmic internal resistance,polarization internal resistance and polarization capacitance as the internal resistance and polarization characteristic parameters of retired batteries,the difference of internal resistance and polarization characteristic parameters of retired batteries with similar residual capacity was analyzed.And the influence of SOC state of batteries on internal resistance and polarization characteristic parameters was studied.On this basis,the separation method of retired batteries based on internal resistance and polarization characteristics was proposed.For retired batteries with similar residual capacity,HPPC test is carried out under the state of 10% SOC,and the internal resistance and polarization characteristic parameters of retired batteries are calculated with the aid of the second-order RC equivalent circuit model;the entropy weight method is used to give weight to each internal resistance and polarization characteristic parameter,and the evaluation value of separation of retired batteries is calculated.According to the difference of evaluation value,the decommissioned batteries can be sorted.Finally,the same type of decommissioned battery were taken as the experimental object to estimate the residual capacity of decommissioned battery based on capacity increment and Gaussian process regression,and compared with the experimental test results to verify the reliability of the residual capacity estimation.The decommissioned battery based on internal resistance and polarization characteristics were sorted,and the capacity attenuation characteristics of each battery were compared to analyzed the rationality of sorting.