We claim the ornamental design for a portable fuel cell system, substantially as shown and described.
FIG. 1 is an exploded front perspective view of the portable fuel cell system in accordance with the present design.
FIG. 2 is a front perspective view of the assembled portable fuel cell system.
FIG. 3 is a front view of the portable fuel cell system.
FIG. 4 is a back view of the portable fuel cell system.
FIG. 5 is a right side view of the portable fuel cell system.
FIG. 6 is a left side view of the portable fuel cell system.
FIG. 7 is a top view of the portable fuel cell system; and,
FIG. 8 is a bottom view of the portable fuel cell system.
The broken lines immediately adjacent to the shaded areas represent the boundaries of the claimed design. All other broken lines are directed to environment and are for illustrative purposes. None of the broken lines form part of the claimed design.