A method of operating a flow battery comprising a stack of flow cells where each flow cell in the stack comprises a fluid permeable electrode, a fluid impermeable electrode, and a reaction zone between the permeable and impermeable electrodes, the method characterised by: (a) in charge mode, plating a metal layer on the impermeable electrode of each cell in the reaction zone by: (i) flowing a metal halide electrolyte from a reservoir through an inlet conduit to the reaction zone of each flow cell in the stack in a first direction, such that a majority of the metal halide electrolyte enters the reaction zone from the inlet conduit without first flowing through the permeable electrode in the flow cell or through a flow channel located between adjacent flow cell electrodes in the stack; and (ii) flowing the metal halide electrolyte from the reaction zone of each flow cell in the stack through a first outlet conduit to the reservoir, such that the majority of the metal halide electrolyte does not pass through the permeable electrode in each flow cell before reaching the first outlet conduit; (b) in discharge mode, de-plating the metal layer on the impermeable electrode of each cell in the reaction zone by: (i) flowing a mixture of the metal halide electrolyte and a concentrated halogen reactant from the reservoir through the inlet conduit to the reaction zone of each flow cell in the stack in the first direction, such that a majority of the mixture enters the reaction zone from the inlet conduit without first flowing through the permeable electrode in the flow cells or through the flow channel located between adjacent flow cell electrodes in the stack; and (ii) flowing the mixture from the reaction zone of each flow cell in the stack through a second outlet conduit to the reservoir, such that a majority of the mixture passes through the permeable electrode in each flow cell before reaching the second outlet conduit. (a) in charge mode, plating a metal layer on the impermeable electrode of each cell in the reaction zone by: (i) flowing a metal halide electrolyte from a reservoir through an inlet conduit to the reaction zone of each flow cell in the stack in a first direction, such that a majority of the metal halide electrolyte enters the reaction zone from the inlet conduit without first flowing through the permeable electrode in the flow cell or through a flow channel located between adjacent flow cell electrodes in the stack; and (ii) flowing the metal halide electrolyte from the reaction zone of each flow cell in the stack through a first outlet conduit to the reservoir, such that the majority of the metal halide electrolyte does not pass through the permeable electrode in each flow cell before reaching the first outlet conduit; (i) flowing a metal halide electrolyte from a reservoir through an inlet conduit to the reaction zone of each flow cell in the stack in a first direction, such that a majority of the metal halide electrolyte enters the reaction zone from the inlet conduit without first flowing through the permeable electrode in the flow cell or through a flow channel located between adjacent flow cell electrodes in the stack; and (ii) flowing the metal halide electrolyte from the reaction zone of each flow cell in the stack through a first outlet conduit to the reservoir, such that the majority of the metal halide electrolyte does not pass through the permeable electrode in each flow cell before reaching the first outlet conduit; (b) in discharge mode, de-plating the metal layer on the impermeable electrode of each cell in the reaction zone by: (i) flowing a mixture of the metal halide electrolyte and a concentrated halogen reactant from the reservoir through the inlet conduit to the reaction zone of each flow cell in the stack in the first direction, such that a majority of the mixture enters the reaction zone from the inlet conduit without first flowing through the permeable electrode in the flow cells or through the flow channel located between adjacent flow cell electrodes in the stack; and (ii) flowing the mixture from the reaction zone of each flow cell in the stack through a second outlet conduit to the reservoir, such that a majority of the mixture passes through the permeable electrode in each flow cell before reaching the second outlet conduit. (i) flowing a mixture of the metal halide electrolyte and a concentrated halogen reactant from the reservoir through the inlet conduit to the reaction zone of each flow cell in the stack in the first direction, such that a majority of the mixture enters the reaction zone from the inlet conduit without first flowing through the permeable electrode in the flow cells or through the flow channel located between adjacent flow cell electrodes in the stack; and (ii) flowing the mixture from the reaction zone of each flow cell in the stack through a second outlet conduit to the reservoir, such that a majority of the mixture passes through the permeable electrode in each flow cell before reaching the second outlet conduit.