Battery Charger Recommendation

I'd recommend the schumacher-10-amp-fully-automatic-or-manual-deep-cycle-battery-charger. It'll charge a deep cycle battery in the manual mode and will automatically charge a car battery in the auto mode. I've had one for several years and love it.
Just my opinion.

I bought three chargers at Harbor Freight. The trickle charger stays on my wife's sportster a lot of the time. The cheap "real" charger stays in the motorhome all the time. The best HF charger stays in the garage. They all work as advertised.

Oh, and I bought the solar panel charger that I used on my wife's grooming van. It worked good as well. For an RV that sits a lot of the time I would think that the solar charger would be the thing to do.

My purpose would be to keep the battery maintained during periods of non use. Not sure what is underkill or overkill - hence my question.

Depends on what your intended purpose is. Some folks think nothing less than a commercial charger capable of 50Amps is barely enouh, while others feel a 15 dollar Harbor Freight trickle charger is just fine.