NOVELTY - A portable fuel cell power source (100) comprises an expandable enclosure (102) containing a first reactant (104); fuel cell(s); a fluid port (112) in the enclosure and in fluidic communication with the fuel cell(s); and an opening (106) to allow for the insertion of a second reactant to the enclosure. When the first reactant is contacted with second reactant a fuel is generated. The volume of the power source in a collapsed state is smaller than the volume of the amount of first reactant and second reactant needed to consume the first reactant in a fuel generation reaction.    USE - As a portable fuel cell power source for generating fuel, including hydrogen (claimed); useful for generating power for electrical appliances or to recharge batteries to power such appliances.    ADVANTAGE - The portable fuel cell power source generates fuel, such as hydrogen, by chemical reaction in a simple and cost-effective manner. The power source has an extended shelf life. It is suitable for emergency or remote power generation to directly power electrical appliances or to recharge batteries to power such appliances. When in non-use, the power source has a stored volume that is minimal so as to increase the energy density of the power source in its stored state. The minimized volume is due to the power source storing as little as one reactant when in its non-use state. The power source may optionally incorporate a self regulating mechanism to limit the rate at which fuel is produced. By incorporating a flexible reactor, the stored volume of the system is much less than the volume required to generate fuel and power. In non-use or storage state, the portable fuel cell power source is compact, dry and sealable to promote convenient transport, long life and provides uncontaminated fuel cells and reactants when needed for use.    DETAILED DESCRIPTION - A portable fuel cell power source (100) comprises an expandable enclosure (102); a first reactant (104) contained within the enclosure; fuel cell(s); a fluid port (112) positioned in the expandable enclosure and adapted to be in fluidic communication with the fuel cell(s); and an opening (106) to allow for the insertion of a second reactant to the expandable enclosure. When the first reactant is contacted with the second reactant, a fuel for use with the fuel cells is generated. The volume of the portable fuel cell power source in a collapsed state is smaller than the volume of the amount of first reactant and second reactant needed to consume the first reactant in a fuel generation reaction. The expandable enclosure comprises a collapsible enclosure. The expandable enclosure comprises a bag. At least a portion of the expandable enclosure comprises a balloon. The portable fuel cell power source further comprises a third reactant, contained within the enclosure; additional chemicals (110) (preferably catalyst or electrolyte) contained within the enclosure; and a self regulating mechanism, enabled by the expandable enclosure.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a portable fuel cell power source.    Fuel cell power source (100)    Expandable enclosure (102)    First reactant (104)    Opening (106)    Additional chemicals (110)    Fluid port. (112)