Weiping Diaoa,b,c, Nan Xuea,b, Vikram Bhattacharjeed, Orkun Karabasoglu e,f and Michael Pecht c
a National Active Distribution Network Technology Research Center (NANTEC), Beijing Jiaotong University, Beijing 100044, China
b Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing Jiaotong University, Beijing 100044, China
c CALCE, Center for Advanced Life Cycle Engineering, Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20740, USA
dDepartment of Electrical & Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
eDepartment of Industrial Engineering, Yasar University, 35100 Bornova, İzmir, Turkey
fSchool of Computer and Information Technology, Beijing Jiaotong University, Beijing 100044, China
Abstract:
The residual available energy (RAE) of a battery pack is an important parameter for determination of the amount
of energy left in the battery pack. The RAE is defined as a function of the cell's initial state of charge (SOC),
discharge current, cell capacity and internal resistance. Battery management systems achieve active equalization
through balancing either the SOC or the terminal voltage of battery packs. Recent research discovered that these
equalization schemes cannot maximize RAE of the battery pack due to the variation of internal resistances and
capacities of the cells in the pack. On the other hand, terminal voltage equalization is not applicable for batteries
having a flat SOC-open-circuit voltage curve. This paper introduces the framework to calculate the RAE of a
battery pack incorporating the variation of internal resistance and capacity of the individual cells in a pack. It
further proposes a novel active battery cell equalization technique based on an RAE maximization scheme. The
effectiveness of the proposed equalization scheme is validated through experimental results with a comparison
of the energy utilization efficiency. The solution methodology and the results are discussed in the paper.
This article is available online here and to CALCE Consortium Members for personal review.