Evaluation of a cell balancing circuit for a new type of high-power density energy storage system

As awareness of human global footprint grows, solutions are investigated to reduce greenhouse gas emission. To accomplish this goal, electrification of our society with low carbon intensity has become a primary goal. Such target can be reached through a large deployment of renewable energy sources, as well as transportation electrification. To help this deployment, the development of economically viable, grid tied energy storage system has become crucial to balance energy production and consumption demands as well as reduce infrastructure upgrade costs to electrical grids. In this context, the main contribution of this paper is to evaluate an active cell balancing circuit for a new type of energy storage cells, called the Carbon-ion (C-ion) cells. Those cells have high longevity and high power density capabilities. They have been assembled into eight packs in series of five cells in parallel. Some cycling and charge-hold testing have been performed on those packs with and without the cell balancing circuit, and the performance of the cell balancing circuit has been evaluated. The active cell balancing circuit prevents the pack voltage from deviating more than ± 0.07 volt from the eight packs voltage mean value during dynamic conditions (cycling) as well as static conditions (charge-hold test). Moreover, it helps to reduce the standard deviation (from 180 F to 71 F) of the apparent capacitance from pack to pack.