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fuel cells are the topic of the text? I don't think the context provided is sufficient to decide either way, but if one of the collaborating companies specialises in aerosol cans, the "batteries" are unlikely to be large, stationary fuel cells. Actually, engineers do refer to "batteries of fuel cells", since the emf required to drive an electric car is many hundreds of V, and therefore very many low-voltage cells arranged in series as a "battery". Much of the impetus for current research is being driven by the motor industry, but other technologies will ultimately benefit from their efforts.
and may merely mean transportable in its working state. 'Battery' isn't perfect here if 'à combustible' was simply omitted for short. We don't call fuel cells 'batteries' in English. (We could: they are 'electrochemical piles' too.)
Much of the industrial R&D on fuel cells to date has focused on stationary power systems.
it depends what you mean by "portable". A "pile" of the atomic type is carried in large warships, submarines and Russian icebreakers, so, in the sense that it is not fixed in the same spot it is "portable". Slightly different from a hearing-aid cell, though.
In France a "pile" is invariably small(ish), and often cylindrical. "Pile" is a bit of a misnomer, and probably dates back to the grandfather of all batteries, Volta's "voltaic pile", which was literally a pile of alternating zinc and copper discs separated by an electrolyte. However, a single 1.5V "pile" is not a "pile" but a radially symmetric 2-electrode system (carbon and zinc in the old days). The little 9V PP3s ARE piles, though. Just to confuse things even more, an "accu", or accumulator, is not what we used to call "accumulators" in the past (which were invariably, but not always, lead-acid cells) has the same size and shape as a small "pile", but is simply rechargeable (NiCd or NiMH). Here, "battery" is perfect!