Thats why I posted a better alternative for EU. Certainly having to pick up double the amount of HCl (which is available in hardware stores for cheap anyway) trumps milking some old car batteries. Not to mention, NEW car batteries have around 40% conc H2SO4, in old car batteries this value will be even lower. So not only will the production and salvaging of these car batteries be highly laborious, it will get a lot worse once you realize that you have to process this H2SO4 as well to get it to high purity. Fractional distillation will only get you so far with this before the sulphuric acid goes azeotropic with the residual water .. around 70ish % without supplemental efforts. But for the HCl generator, this is not concentrated enough.
So unless you still have access to H2SO4 freely in Europe, a HCl/CaCl2 generator is definitely the better option this side of the pond.