When your mechanic tells you your battery's electrolyte level is low, it means the fluid level in one or more of the battery cells has dropped below the top of the lead plates. What does that mean? Car batteries are composed of a series of lead plates submerged in a bath of water and sulfuric acid. This creates a chemical. The only electrolyte that can be used in a lead-acid battery is sulfuric acid. Adding anything but water to a battery can instantly damage it, but some substances are worse than others. For example, baking soda can. Water, on its own, is not an electrolyte. It can only be an electrolyte when mixed with sulfuric acid, so it stands to reason that you would have to top. Although you can prolong the life of a lead acid battery by keeping it topped off, leaving it empty, or allowing the charge to drain too low, can cause irreparable harm. Once a battery reaches a.