A hybrid flow battery is a type of flow battery that includes a deposition reaction at the negative electrode; therefore, the volume available in the negative electrodes of the stack limits the total energy that can be stored by such a battery. In this paper, the plating capacity of a porous carbon felt in a hybrid flow battery with a flow-through geometry was examined by copper deposition from a mixed Cu-Fe sulfate chemistry. Due to uneven current distribution across the porous electrode, at most only 23% of the available volume was actually usable for metal deposition before the battery failed. The percentage of volume able to be utilized varied with the applied current density. A model for predicting this plating utilization as a function of the porous electrode characteristics, electrolyte properties, and current density was developed, and ways of improving the current distribution to achieve higher plating utilization were examined. Even under non-optimized conditions, plating densities in excess of 560 mAh cm(-2) were achieved. (C) The Author(s) 2015. Published by ECS. All rights reserved.