Abstract

This paper presents a novel grouping method for lithium iron phosphate batteries. In this method, a simplified electrochemical impedance spectroscopy (EIS) model is utilized to describe the battery characteristics. Dynamic stress test (DST) and fractional joint Kalman filter (FJKF) are used to extract battery model parameters. In order to realize equal-number grouping of batteries, a new modified K-means clustering algorithm is proposed. Two rules are designed to equalize the numbers of elements in each group and exchange samples among groups. In this paper, the principles of battery model selection, physical meaning and identification method of model parameters, data preprocessing and equal-number clustering method for battery grouping are comprehensively described. Additionally, experiments for battery grouping and method validation are designed. This method is meaningful to application involving the grouping of fresh batteries for electric vehicles (EVs) and screening of aged batteries for recycling.

Highlights

  • With the development of electric vehicles (EVs), battery technology has drawn more and more attention worldwide.Battery packs are core components of EVs; they are composed of hundreds or thousands of small cells joined by series-parallel connections

  • After review of the problems of the battery consistency evaluation parameter extraction methods and battery clustering algorithms, this paper presents a novel battery grouping method

  • Recent battery models mainly involve equivalent circuit models based on the external electric characteristics of battery charge and discharge (ECMs for short in this paper) or electrochemical impedance spectroscopy tests (EIS models), electrochemical reaction mechanism models (ERM models), etc

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Summary

Introduction

With the development of EVs, battery technology has drawn more and more attention worldwide. Battery capacity, AC resistance, electrochemical impedance spectroscopy (EIS), voltage curve, battery model parameter, charge and discharge thermal behavior are the commonly used parameters to evaluate consistency. After review of the problems of the battery consistency evaluation parameter extraction methods and battery clustering algorithms, this paper presents a novel battery grouping method The clustering algorithm can divide the batteries into equal-number groups according to the similarity of consistent evaluation parameters and the number of elements designed by engineers in each group

Comparison of Battery Models
Simplified EIS Model
Model Parameter Identification
Model State Equation Establishment
X W 0
Parameter Identification Experiment Sequence
Data Down-Sampling
Crude Data Exclusion
Consistency Evaluation Parameter Generation
Battery Equal-Number Clustering
K-Means Clustering Method
Kd-Tree Cluster Center Initialization
The New Modified K-Means Clustering Method
Experimental Details
Model and Parameter Identification Verification Experiments
Battery Grouping Verification Experiments
Battery Parameter Identification Result Analysis
Battery Clustering Result Analysis
Model Accuracy Verification
Model Parameter Identification Accuracy Verification
Battery Grouping Accuracy Verification
Conclusions
Conflicts of Interest
Background
Full Text
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