The Water Miser Battery Cap is designed to reduce battery maintenance by decreasing the frequency with which distilled water needs to be added to each cell. Each cap has condensing pellets within its flip top lid which capture and return electrolyte droplets into each cell as battery charging takes place. This process does NOT eliminate the need to add distilled water! Each battery cell needs one Water Miser Cap which will replace the original cell's cap.
These are what Shawn at Backwoods uses with his HUP Solar-1 batteries at his off grid residence.