You might notice a sticky dark gray residue on the inside of the R-Caps or Watermiser vent caps on each battery cell.  This buildup of dried electrolyte is fairly common and may be flushed clear using a neutralizing baking soda and water solution .

Clean the Rolls R-Caps or Watermiser caps by soaking them in a 10 to 1 water to baking soda solution in a bucket or small bowl. 

Let the vent sit overnight to neutralize and break down any electrolyte in the caps. Next, take a closed cap and force water through the vent holes in the flip-top. Water should drip freely through vent holes. A trickle of water should flow from all 4 vent holes. If water flows through the vent holes the pathway is clear. Allow the vents to dry completely.

Once dried, shake the vent to make sure the condensing beads on the inside of the cap rattle slightly. If you do not hear the beads, let the cap dry for an additional 12 hours or repeat the process above.