Embodiments of the present invention relate to a portable fuel cell power source including an expandable enclosure, a first reactant contained within the enclosure, one or more fuel cells and a fluid port positioned in the expandable enclosure and adapted to be in fluidic communication with the one or more fuel cells. The enclosure may also include an opening to insert a second reactant. When the first reactant is contacted with the second reactant a fuel is generated for use with one or more of the fuel cells. The volume of the portable fuel cell power source in a collapsed state may be smaller than the volume of the amount of first reactant and second reactant needed to substantially consume the first reactant in a fuel generation reaction.