Abstract: A redox fuel stack cell comprises a plurality of essentially similar half-cell frames of molded polymer; interleaved between them are semi-permeable membranes and bipolar plate electrodes. The frames are rectangular, with margins around central voids. At the voids, they have rebates in abutting faces for locating the plate electrodes. At their corners, they have apertures for forming ducts throughout the stack for flow of electrolyte to and from the cell cavities provided by the voids. The frames have electrolyte flow passages open in their faces abutting the frames and leading towards each other. The passages stop short of each other and are surrounded by grooves containing sealing O-rings. Diagonally opposite one of the passages end at openings passing through the frames. The other passages have no openings in the frames, but the frames have openings through them in register with the ends of the passages.

Abstract: A redox fuel stack cell comprises a plurality of essentially similar half-cell frames of molded polymer; interleaved between them are semi-permeable membranes and bipolar plate electrodes. The frames are rectangular, with margins around central voids. At the voids, they have rebates in abutting faces for locating the plate electrodes. At their corners, they have apertures for forming ducts throughout the stack for flow of electrolyte to and from the cell cavities provided by the voids. The frames have electrolyte flow passages open in their faces abutting the frames and leading towards each other. The passages stop short of each other and are surrounded by grooves containing sealing O-rings. Diagonally opposite one of the passages end at openings passing through the frames. The other passages have no openings in the frames, but the frames have openings through them in register with the ends of the passages.

Abstract: A redox flow battery 1 has a stack of individual cells, shown diagrammatically as a single cell, with anolyte and catholyte compartments divided from each other by an ionically selective and conductive separator and having respective electrodes. The battery has anolyte and catholyte tanks, with respective pumps and a pipework. In use, the pumps circulate the electrolytes to and from the tanks, to the compartments and back to the tanks. Electricity flows to a load. The electrolyte lines are provided with tappings via which fresh electrolyte can be added and further tappings via which spent electrolyte can be withdrawn, the respective tappings being for anolyte and catholyte. On recharging, typically via a coupling for lines to all the tappings, a remote pump pumps fresh anolyte and fresh catholyte from remote storages and draws spent electrolyte to other remote storages.