Design of novel charge balancing networks in battery packs

In a modern battery pack, the charge in the individual cells can diverge in time, leading to decreased capacity and reduced operating life of the pack. Charge balancing systems can be introduced to equalize the state of charge across the multiple cells, therefore increasing the performance of the battery pack. This work considers the dynamic performance of charge balancing systems, and through simulation explores how their ability to equalize the state of charge depends on the design of the underlying charge balancing network. The performance of the charge balancing system is described in terms of the rate at which the individual cells converge and the maximum cell voltage deviation in the pack. Specifically the performance of the charge balancing system is shown to correlate with graph theoretic properties of the underlying charge balancing network, including the diameter and spectral gap. Several different underlying charge balancing networks are considered, applied to an 8-cell pack, with two parallel strings of four cells in series. (C) 2013 Elsevier B.V. All rights reserved.