HC, are you sure about that? I thought is was lower.
One thing about battery acid: If you are using a depleated lead-acid battery, the concentration will be lower than a fully charged one.
If it were I, I would obtain some drain cleaner.
It would be a good thing to use an inline drier as well. It isn't fun to loose 1/2 your product gassing because you have H2O in your gas.
I would do some more reading before I tried this. If you don't understand what is happening, you can easily flood the whole room with HCl gas. Hell, you can have an accident if you do understand it. No dissrespect intended, it's just gassing can be dangerous.