Hammick - I bought
Meanwell SE-200-15 for $38 for the same purpose, only for a car battery - to bring it back in shape after long absence. My RV bank is taken care of by solar, works like a charm. This my 10A Minny will be adequate for what you want - top charging and equalization, since you are not looking for high current and/or charging a big bank from the scratch. I'm not sure that a 30A Meanwell/Megawatt for $60 is any better in this case, since you don't need a lot of amps.
What nobody told me is that Meanwell/Megawatt is a barebone system. You get what you see - no voltmeter, no cables, no handy knobs. Not even legs - you know, those small bumps or plastic washers at the bottom, so it won't be sitting with its hot ass on a wooden bench. I attached an old lamp cord, and a cord with crocodiles from a dead charger. I wrote about this already - tiny adjustment knob on Meanwell (the knob on Megawatt looks similar) is not for playing with it very often. It is small and flimsy, requires a careful handling with a small screwdriver, checking on multimeter after every micro-movement of your wrist to make sure that it's 13.7V and not 13.9, or whatever you need it to be.
That Ebay charger looks more user friendly than Meanwell/Megawatt. But I don't know who and how makes them. Voltmeter and ammeter - I don't know how good they are. Have a 4-digit voltmeter from Amazon (2 decimal points), it works with 0.3V error which makes it pretty much useless. Mean/Mega are made well, this I know.
Converters - they work as long as your batteries are in a trailer. If you remove them to some garage for long-term storage, converter won't be much useful.
