A frame assembly for a fuel cell power module, particularly but not exclusively for use in lift trucks, has at least one frame element. The frame element is provided with an internal cavity that is filled with a fill material to provide a desired mass of the frame assembly. The frame assembly is configured to receive a fuel cell stack and other balance of plant components of a fuel cell power module and may also be configured to receive a fuel storage vessel. The frame assembly can be configured so that it can replace a battery pack of a lift truck and still provide adequate counterweight.