What Happens If You Put Tap Water In A Battery. To be safe distilled water is your best bet and is a much smaller investment than a new battery. Dont Over Water If too much water was added before charging the electrolyte levels will expand and cause the battery to overflow and damage the battery.
Remember that water will sit on top of the acid solution in your battery until it is mixed by the bubbling produced by charging. Deep discharges heat vibration fast charging and overcharging all accelerate the aging process. The minerals in the tap water coats the plates and fills the pores so they are no longer in contact with water but with the minerals which causes the over working of the battery.
Using ordinary tap water or softened water is bad for your deep-cycle batteries as the minerals found in the water can react with the electrolyte and minimize performance and increase sediments.
Deep discharges heat vibration fast charging and overcharging all accelerate the aging process. Additionally excessive watering of a battery can result in additional dilution of the electrolyte resulting in reduced battery performance. As I mentioned in a comment the electrical conductivity of tap water is pretty low so while current definitely did flow while underwater it was only a small amount hardly enough to drain the battery. Ordinary tap water should not be used because it may contain an excessive amount of impurities that will degrade battery performance.
