Qwik-Fill is for 12V batteries. Pro-Fill is for 6V batteries. According to the FAQ's "A maximum of 6 batteries can be plumbed together with the Pro-Fill RV Edition system, although many users prefer (for ease of filling) to limit the number of batteries plumbed together at 4."
Chuck & Teri, 1999 35 ft. Dolphin 5350, F53 Chassis with tag axle, Chassis build date 1/99 in Mexico, Banks System, Trans Command, Air Lift Air Bags on rear, Koni Shocks, Blue OX TruCenter, TigerTrak track bars front and rear, Roadmaster 1-3/4" rear auxiliary sway bar, 2013 VW Passat TDI SEL Premium, 1994 36 ft. Avion 5th Wheel. FMCA #F430129