To clear you guys doubt about the battery water.....
1st...the water inside the bottle is not ACIDIC...is just distilled, unmineralized water. It's does not harm....
2nd, the battery water will become acidic when electrolysis happens.
Read here:
http://en.wikipedia.org/wiki/Lead-acid_battery
In the case of a wet cell battery, the liquid (battery water) is known as an electrolyte.
From my knowledge , the lead acid battery contains 6 plates each producing 2V so 6 by 2 is 12 so you get a total of 12V. You can see this because you have 6 filling holes for the battery water.
The reason that distilled water is used because normal waters contains too much mineral and other substances that might make the battery to under perform and causing the electrolysis process to be unstable or not at a high efficiency.