A hydrogen-ion based battery cell which includes two electrodes (4,5) containing metal current collectors (1,2), and porous carbons with a catalyst and respectively saturated with hydrogen and oxygen. An ion conducting membrane (3) is located vertically between the electrodes, and has a sandwich construction, with a liquid electrolyte (34A) trapped between two porous, electrically non conductive and ion permeable sheets (11A,12), which are however not liquid permeable. A liquid electrolyte (33) is contained in two separate chambers (10,11) under the electrodes which are connected by a tube or tunnel (13) to keep the electrolyte in equilibrium in both chambers.    Two horizontal filters (14,15) permeable by liquids and gases are located under the electrodes to separate the carbons and catalyst of the electrodes from the electrolyte, and two additional electrodes (8,9) are submerged in the electrolyte separately in the electrolyte chambers. An electrically insulating gas-liquid sealing housing encompasses the above components and is divided by the membrane into two halves (6,7) which are hermetically sealed to the membrane.    Pref. the electrode carbon is of the form of activated carbon, super-activated carbon, buckminster fullerene i.e. C60 and/or carbon black, and the electrode catalyst is of platinum, palladium and/or nickel. The membrane sheets are made of microporous polytetrafluoroethylene or Nafion, and the electrolytes contain water and an acid, salt or a base e.g. potassium hydroxide. The current collectors and/or additional electrodes are made of a metal plated carbon fibre net, a polymer fibre fabric net, or carbon, and the horizontal filters are made of a ceramic sponge and a porous membrane. The housing is made of a honeycomb sandwich polymeric material or of a metal plated or metallised polymeric material.    USE -   The battery is used in motor vehicles and cycles, and other vehicles requiring electric power e.g. cars, boats, aircraft in e.g. military applications, for e.g. the cranking of engines. For load levelling energy storage and un-interruptible power supplies, or other applications requiring high energy-power density or long cycle life.    ADVANTAGE -   The battery has a relatively high gravimetric energy and power density (i.e. w.r.t. Watts and Watt-hours per kilogram), by avoiding the use of heavy metals and heavy metal oxides in its electrodes, heavy metal current collectors and heavy packaging. Also it is cheaper, and less toxic, thus facilitating recycling.