Flow batteries are electrochemical energy storage systems in which electrochemical reactants are dissolved in a solvent such as water. The liquid electrolytes are pumped through reaction cells where electrical energy is either converted to or extracted from chemical potential energy in the reactants by way of reduction and oxidation reactions. In applications where megawatts of electrical energy are to be stored and discharged, a redox flow battery system can be expanded to a required energy storage capacity by increasing tank sizes. A flow battery system may be expanded to produce the required output power by increasing the number or size of electrochemical cells or cell blocks. A variety of flow battery chemistries and arrangements are known in the art.