To improve the way in which a fuel
cell is installed, especially in the case of
fuel cells on board electric traction vehicles, the
oxygen needed for supplying the fuel
cell is produced in situ by separating the
nitrogen from the
ambient air continuously, without a change of state. Thus, an
electric power pack comprises a stack of
electrochemical cell elements each possessing a
cathode and an
anode, in electrochemical
coupling relationship with an
electrolyte, and an electrical output circuit suitable for connecting the
cathode and the
anode through a load, a device for delivering fuel to the
anode and an on-board
oxygen generator based on a separator, for separating the
oxygen and
nitrogen of the
ambient air without a change of state, in order to supply the
cathode of said
cell elements. According to a preferred embodiment, the separator is of the
nitrogen pressure swing adsorption type. In one embodiment, the separator is supplied with
compressed air by a first compressor and the oxygen delivered at its output is compressed further in order to supply the fuel cell. The whole
assembly makes it possible to achieve an
improved performance compromise for vehicle applications in which great autonomy is required.