[Christ]

Chuckm - Not to be a smart ass, but don't batteries produce hydrogen as the electrolyte level drops? (I was under the assumption that the "Vented" gas is a mix of hydrogen and other gasses, since it's supposedly flammable (I've never tested, so supposedly))

I would guess that, if it were true, extracting that gas would probably be the cheapest way, per unit, to get H2, since it's a waste product, easily captured.\

Of course, you'd never get even close to enough to have an effect on a vehicle, either.