We studied the capital cost associated with the acid-base crossover. The cost estimate in this section is independent of the three-chamber battery system cost. The capital cost of a BPM recovery subcell can be assigned into two parts. The first part is the BPM recovery sub-cell cost. If the acidbase crossover is more severe, assuming a minimally sized BPM recovery sub-cell that operates constantly, we will have to use a larger BPM recovery sub-cell. The second part is the energy consumed by acid-base recovery. Capacity utilized in the recovery process cannot be counted into the energy storage capacity.