What battery charger for winter storage?

My boat is stored outside, car is garaged. Some of us boaters go a little (lol, a lot) overboard with the batteries. After winterizing the engine I full charge them before moving them onto a cart in the basement. I also pull the onboard charger to maintain them once a month or so.
http://www.dualpro.com/products/professional-series/
My car, I just disconnect the battery and clip on the old 2/6 amp sears charger for an hour or two.