Which magic elixir was that? I've yet to find someone who used one, and still had good batteries six months later. But I'm willing to look & learn!
I used "Battery Equaliser", but in all honesty I think reviving the batteries had a lot more to do with modern microprocessor controlled charger than with that stuff (hard to tell now, I did both things at about the same time).
I am yet to try using equalization mode of the charger - may be my battries will be even more lively then (but in any case even 70% of the full charge is plenty in my case).
Those automotive chargers are definitely not very good, and my past experience with them was pretty marginal - they certainly don't charge a battery to a full capacity and won't bring back it's useful life.