Weiping Diao 1, Michael Pecht 1, and Tao Liu 2
1CALCE, Center for Advanced Life Cycle Engineering, Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20740, USA
2b State Key Laboratory of Fluid Power and Mechatronic Systems, College of Mechanical Engineering, Zhejiang University, 310027, Hangzhou, China
Abstract:
Uneven electrical current distribution in a parallel-connected lithium-ion battery pack can result in different
degradation rates and overcurrent issues in the cells. Understanding the electrical current dynamics can enhance
configuration design and battery management of parallel connections. This paper presents an experimental
investigation of the current distribution for various discharge C-rates of both parallel-connected LiFePO4 and Li
(NiCoAl)O2 cells. A first-order Thevenin model for current distribution calculation was applied to assess the
maximum discharge current discrepancy between cells when the number of cells increases. This study reveals
why balancing circuits are seldom implemented on cells in a parallel connection, and provides guidance on
reducing cell imbalances by managing battery operation in terms of state of charge range and discharge C-rates,
as well as improving connection design.