A flow battery system and method are provided. The flow battery system includes a first battery stack including a first half-cell, a first pressure feed system, including at least a first storage tank and a first booster tank to store a liquid electrolyte, designed to generate a first booster pressure in the first booster tank sufficient to force the liquid electrolyte to be fed from the first pressure feed system through the first half-cell, and a return system to return the liquid electrolyte from the first half-cell to the first pressure feed system. The return system may include a gravity feed system returning liquid electrolyte from the first half-cell to a collection tank, and a pump to return the collected liquid electrolyte from the collection tank to the first storage tank. The pressure feed flow battery system may have a two-tank, divided 2-tank, or four-tank flow battery configurations.