Watering Your Battery
"There are two conditions when watering can be harmful to your batteries. One is over-watering and the other is under watering. It seems like most everyone does one or the other. In our recent meeting with the Trojan battery gurus, they told us that over-watering is perhaps more harmful to the batteries than under watering, but they are both bad for the batteries. So we will discuss over-watering first.
Over-Watering Your Batteries The electrolyte in a battery is the solution of water and sulfuric acid. During the normal process of charging and discharging the level of the electrolyte changes rather drastically. This is normal. It is also normal in the process of charging to lose some of the electrolyte. We'll explain how this happens in a moment. So it is necessary periodically to bring the electrolyte level to a correct level by adding water and distilled water is HIGHLY recommended. But adding water is where things can get screwed up. This is how it happens. You come home from playing a round of golf and think, just before you recharge the batteries, "Gosh, I'd better check the batteries. I haven't put water in them for quite some time." So you open up the battery compartment and remove the caps guarding the cells and low and behold, the electrolyte level is low. So you get a jar or can and fill it with tap water and start pouring it into the cells. Oops, got too much in that one, its overflowing. Oh well, not to worry. Wrong! Wrong! Wrong! You just made three mistakes, all bad for your batteries."