So, chemistry expert wasn't too much help we had to Google Alum bet the consensus after two pubs (normal quiz has been permanently cancelled and we're trying to find a good alternative) and many beers, was that any electrolyte would probably work, but not as a well as sulfuric.
I'll still have a play when I have a moment.
On a similar note, the twin battery set up on the Disco (mentioned a while back) is working well with no obvious drawbacks.