Water should only be added after fully charging the cart.  Prior to charging, there should be enough water to cover the plates.  If the battery has been discharged (partially or fully), the water level should also be above the plates. Important things to remember:  Do not allow plates to be exposed to air.  Do not fill the water all the way up to the caps.  Do not use water with high mineral content.  Use only Distilled or Deionized water.  To water the batteries:  Remove the vent caps and check the electrolyte level; the minimum level is to the top of the plates.  If there is No electrolytes visible, add just enough water to cover the plates.  Replace and tighten all water vent caps.  Put batteries on a complete charge before adding any more water.  Once the charging is complete, remove the vent caps and check the electrolyte level.  Add water until the electrolyte level is 1/8" BELOW the bottom of the fill well.  Clean, replace and tighten all vent caps.