A Study of Cell-to-Cell Interactions and Degradation in Parallel Strings: Implications for the Battery Management System

JOURNAL OF POWER SOURCES

卷:329

Article

Pastor-Fernandez, C.¹  Bruen, T.¹  Widanage, W. D.¹  Gama-Valdez, M. A.²  Marco, J.¹ 

[1] Univ Warwick, WMG, Coventry CV4 7AL, W Midlands, England

[2] Jaguar Land Rover, Banbury Rd, Warwick CV35 0XJ, England

关键词: Lithium ion technology;    Battery pack;    Battery management system;    State of health estimation;   

DOI  :  10.1016/j.jpowsour.2016.07.121

来源: Elsevier

【 摘 要 】

Vehicle battery systems are usually designed with a high number of cells connected in parallel to meet the stringent requirements of power and energy. The self-balancing characteristic of parallel cells allows a battery management system (BMS) to approximate the cells as one equivalent cell with a single state of health (SoH) value, estimated either as capacity fade (SoHE) or resistance increase (SoHp). A single SoH value is however not applicable if the initial SoH of each cell is different, which can occur when cell properties change due to inconsistent manufacturing processes or in-homogeneous operating environments. As such this work quantifies the convergence of SoHE and SoHp due to initial differences in cell SoH and examines the convergence factors. Four 3 Ah 18650 cells connected in parallel at 25 degrees C are aged by charging and discharging for 500 cycles. For an initial SoHE difference of 40% and SoHp difference of 45%, SoHE converge to 10% and SoHp to 30% by the end of the experiment. From this, a strong linear correlation between ASoHE and SoHp is also observed. The results therefore imply that a BMS should consider a calibration strategy to accurately estimate the SoH of parallel cells until convergence is reached. (C) 2016 The Authors. Published by Elsevier B.V.

【 授权许可】

Free