Can Bottled Water Be Added to a Battery?by Emily Manthei
Although most batteries on new or nearly-new cars are sealed and don't require any maintenance, older car batteries require the occasional top-up of water every few months. Once you remove the cap, refill the battery cells individually.
Bottled or Tap?
Because tap water contains minerals and natural content that could corrode the battery, it's best to used bottled water. Use distilled or deionized water to fill your battery, as it doesn't contain the mineral content of tap water. Check the label of bottled water to make sure it's distilled and does not have natural mineral content.
The battery contains ionized electrolytes that need to be diluted by water. This makes using deionized water essential because it will dilute -- not contribute to -- the charge of the battery.
Distilled water is free from the calcium and mineral deposits found directly at the spring. This water is more neutral, making it ideal for contributing to the battery.