Large-scale lithium-ion battery packs are widely adopted in systems such as electric vehicles and energy backup in power grids. Due to factors such as manufacturing difference and heterogeneous discharging conditions, cells in the battery pack may have different statuses, such as diverse voltage levels. This cell diversity is commonly known as the cell imbalance issue. For the charging of battery packs, the cell imbalance not only early on terminates the charging process before all cells are fully charged, but also leads to different desired charging currents among cells. In this paper, based on the advancement in reconfigurable battery systems, we demonstrate how to utilize system reconfigurability to mitigate the impact of cell imbalance on an efficient charging process. With the proposed reconfiguration-assisted charging (RAC), cells in the system are categorized according to their real-time voltages, and the charging process is performed in a category-by-category manner. To charge cells in a given category, a graph-based algorithm is presented to charge cells with their desired charging currents, respectively. We evaluate RAC through both experiments and simulations. The results demonstrate that the RAC increases the capacity charged into cells by about 25% and yields a dramatically reduced variance.
Bibliographical noteFunding Information:
This work was supported in part by the Key Laboratory of Computer Network and Information Integration (Southeast University), Ministry of Education under Grant K93-9-2015-02B, in part by the Shanghai Recruitment Program of Global Experts, in part by the National Natural Science Foundation of China under Grant U1334202 and Grant 61303202, in part by the Fundamental Research Funds for the Central Universities under Grant 2015RC032, and in part by China Post-Doctoral Science Foundation under Grant 2014M560334.
© 2016 IEEE.
- Battery charging
- cell imbalance
- reconfigurable battery packs