Cell imbalance, a notorious but widely found issue, degrades the performance and reliability of large battery packs, especially for cells connected in series where their overall capacity delivery is dominated by the weakest cell. In this paper, we exploit the emerging reconfigurable battery packs to mitigate the cell imbalance via the joint consideration of system reconfigurability and State-of-Health (SoH) of cells. Via empirical measurements and validation, we observe that more capacity can be delivered when cells with similar SoH are connected in series during discharging. Based on this observation, we propose two SoH-aware reconfiguration algorithms focusing on fully and partially reconfigurable battery packs, and prove their (near) optimality in capacity delivery. We evaluate the proposed reconfiguration algorithms analytically, experimentally, and via emulations, showing 10%-60% improvement in capacity delivery when compared with SoH-oblivious approaches, especially when facing severe cell imbalance.
Bibliographical noteFunding Information:
Manuscript received June 3, 2016; revised October 18, 2016; accepted November 27, 2016. Date of publication December 14, 2016; date of current version June 19, 2018. This work was supported in part by the NSF under Grant CNS-1329702, Grant CNS-1446117, and Grant CNS-1503590, and in part by the State Key Laboratory of Industrial Control Technology under Grant ICT1600206 and Grant NSFC-61402372. An early version of this work is published at ICCPS’15 . Paper no. TSG-00747-2016. (Corresponding author: Zhe Yang.) L. He is with the University of Colorado Denver, Denver, CO 80204 USA. K. G. Shin is with the University of Michigan, Ann Arbor, MI 48109 USA. Z. Yang is with Northwestern Polytechnical University, Xi’an 710072, China (e-mail: email@example.com). Y. Gu is with IBM Watson Health, Austin, TX 78613 USA. C. Liu is with the University of Texas at Dallas, Richardson, TX 75081 USA. T. He is with the University of Minnesota, Minneapolis, MN 48109 USA. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TSG.2016.2639445
- Reconfigurable battery packs
- cell graph
- cell imbalance