Bass Pro Shops 5/5 battery charger

I just got one of the Bass ProShops battery XPS 5/5 two bank battery chargers and when I hooked it up it charges the battery very quickly to 14.4v and then the lights start blinking and the voltage begins to drop very quickly and continues to drop past 11v so I unplug it. Oringinally I thought that maybe I had something in the boat stereo wired wrong so I disconnected all wires from the two batteries and just hooked up the charger/tender, it did the same thing. Charged them to 14.4v rapidly and then started to drop off just as fast down to 11v. This all happens within 3-4 minutes of plugging it in. I think I'm going to have to send the charger back to Bass Pro Shops.