NOVELTY - Fuel cell system comprises a power source having cell cavities, a fuel storage unit, a first flow path for providing fuel from fuel storage unit to power source, a second flow path for providing fuel which has not been deposited into the cell cavities back to fuel storage unit, and a third flow path for providing unused and/or partially used fuel, reaction product(s), and/or spent reaction solution to fuel storage unit and/or second flow path.    USE - For providing primary and/or backup power to electrical or electronic equipment, e.g. lawn and garden equipment; radio; telephone; targeting equipment; battery recharger; laptop; communication device; sensor; night vision equipment; camping equipment (including stove, lantern, and light); vehicle (including car, recreational vehicle, truck, boat, ferry, motorcycle, motorized scooter, forklift, golf cart, lawnmower, industrial cart, passenger cart, luggage handling equipment, airplane, lighter than aircraft, hovercraft, train, and submarine); torpedoes; security system; and electrical energy storage device for renewable energy sources (e.g. solar-based, tidal-based, hydro-based, or wind-based).    ADVANTAGE - The fuel cell system provides longer-term primary and/or backup power efficient and compactly relative to traditional power sources.    DETAILED DESCRIPTION - Fuel cell system comprises a power source (508) having at least one cell cavity, a fuel storage unit for containing flowable fuel, a first flow path for providing flowable fuel from the fuel storage unit to the power source, a second flow path for providing flowable fuel which has not been deposited into the cell cavities back to the fuel storage unit, and a third flow path for providing unused and/or partially used fuel, reaction product(s), and/or spent reaction solution to a reaction product storage unit, fuel storage unit, and/or second flow path.    DESCRIPTION OF DRAWING(S) - The figure is a block diagram of the inventive fuel cell system.    Pump (506)    Power source (508)