1,186,502. Electrolyte circulation valves. JOSEPH LUCAS (INDUSTRIES) Ltd. 7 June, 1967 [June, 27 1966], No. 28704/66. Heading H1B. The invention comprises a zinc-air battery in which electrolyte flows through all the cells in series characterized in that the cells are isolated from one another by valves which are closed when the electrolyte is stationary but open automatically when it begins to flow. In a typical embodiment (Figs. 2 and 3) bipolar electrodes comprising zinc-plated steel anodes backed with porous nickel cathodes, are retained in plastics frames 21 and bolted into a stack together with terminal end plates 24 and 25. Leakage between the cells is prevented by sealing rings 26 (Fig. 3). Air is supplied to the cathodes by manifold 18 and leaves by manifold 19. Electrolyte enters the cells from manifold 16 and leaves via manifold 17. Manifold 16 contains spring-loaded valves 28 (Fig. 3) which close when the electrolyte is stationary but open when it flows.