With all this talk about using Evian and Perrier for a battery, I think may be important to point out that there is a HUGE difference between spring water (evian, perrier, etc) and distilled water... If the trace elements in tap water will 'hurt' a battery, they should burst into flames upon contact with spring water! I realize that you guys probably already know this, but this is just in case....
The reason I brought it up is because my wife has this fish, see... This fish lives in a vase full of DISTILLED water, with a houseplant in it.. You guys know, the kind where the fish eats the plant to live, blah blah blah.. You guys have probably seen them, right? Anyway, she's had her fish for about 20 months, and he's great... She never even has to clean the vase! We know other people who have fish like this, and they seem to last about 6 mos, MAX... Their vases get REALLY CRAPPED UP looking (trace elements), and when asked what kind of water they use, they usually say 'spring water.' We always tell them to switch to distilled water instead, and you'd be surprised how many people ask, 'what's the difference?' Man, I'd hate to see someone ruin a battery thinking they would give go the 'extra mile' and give it the best water money could buy!