Consistency Analysis Of Power Lithium Battery Based On Improved DQ/dV

In recent years,the development of electric vehicles has become more and more rapid.Among them,the key power supply is becoming more and more prominent due to the consistency problems that occur in the manufacturing process.The inconsistency of the battery pack seriously affects the actual service life of the electric vehicle.,Even in serious cases,there will be security problems.This paper conducts the following research on the consistency of battery packs.This article focuses on the ternary battery,studies the battery performance at different temperatures,different rates,and aging conditions,analyzes the battery capacity changes,and conducts basic battery performance studies.For the current battery consistency screening methods such as capacity screening,voltage screening,internal resistance screening and other single screening or multi-parameter screening methods.It is proposed that the current method performs parameter screening from outside the battery,which has certain limitations.To study the battery screening method,we should start with the principle of electrochemical reaction,study the internal parameters of the battery,and then use the d Q/d V curve to improve consistency.The electrochemical interface reaction and mass transfer process of the battery are studied.It is found that the electrochemical model is very complex and has many inconveniences during use.The d Q/d V curve(capacity increment curve)is an effective tool for analyzing the battery state inside the battery.This method is A method to obtain the internal parameter status of the battery without disassembling the battery at all.The change of the curve corresponds to the electrochemical state of the battery.Screening battery consistency from the perspective of battery electrochemical state has better screening performance than traditional charge and discharge curves.When studying the d Q/d V curve,it is found that the drawing of the curve is limited by the data processing method.At present,most of the data processing uses equal voltage intervals or equal capacity intervals.However,even under laboratory conditions,the problem of missing data points is still found,causing a large curve error.In response to this phenomenon,the author proposes to perform curve fitting to obtain the missing points.At the same time,according to the fitted curve,a square d Q/d V curve is obtained and compared with the drawing of equal voltage intervals.After verification,the curve obtained by this method has good accuracy.At the same time,the square curve is more conducive to the rapid estimation of battery capacity.Further,the experiment was conducted under different temperatures,different magnifications,and different aging conditions to verify that it has good robustness and an improved d Q/d V curve.In order to study the influencing factors of battery consistency,d Q/d V curves are drawn under different stresses to obtain curve parameters.It is found in the research that most of the parameters have multicollinearity,and it is impossible to directly curve fit the parameters and analyze the change of the curve parameters.In order to overcome the multicollinearity,the partial least squares algorithm is used to analyze the battery parameter changes under different stresses.In order to study the importance of the parameters to the curve,the variable projection importance index is introduced to judge the parameter importance.Finally,the experimental group was screened using the parameters obtained by screening,and compared with the control group screened by using traditional consistency screening parameters such as voltage,internal resistance,capacity,etc.,using constant current battery charging and constant current discharge tests at different temperatures,Proved the effectiveness of the screening parameters,and obtained a capacity increase of more than 10%.