Research on screening of lithium battery based on capacity-voltage second derivative and equalization charging technology

Abstract

In order to solve the problems of slow speed and low accuracy of current screening of lithium batteries with different performance., a fast screening method for lithium batteries was proposed based on the second derivative of capacity-voltage discharge curve, and the 3.4V voltage point was taken as the feature point for screening. This method is faster than the traditional method, and the accuracy can be improved to more than 90%; In order to solve the problem of overcharging and other imbalance in lithium battery charging, a multi-mode serial-parallel conversion circuit was proposed, which takes 3.4V as the starting voltage of charge control, which can effectively equalize the charge of battery pack and eliminate the inconsistencies between batteries. After equalization charging, the voltage difference between battery packs can be reduced to less than 1mV.