Energizers Duo really stood by its products name. Should you have been one of the lucky purchasers of the Energizer Duo battery charger you may have inadvertently downloaded a virus along with the software that allows you to watch your batteries charge. It basically Duo'd as a charger and virus spreader.
Filling a large bank (or multiple banks) of batteries can be a time consuming and somewhat dangerous process. For larger applications you have to open, recap and fill each battery individually which can be time consuming when done over multiple banks. Also as you are exposing yourself to raw battery acid, often in somewhat awkward positions there is the potential for overfilling or splashing of battery acid. The HydroLink system takes care of this by allowing you to fill multiple batteries at once from a single water source.