Hi DJ,
My old multi-stage battery charger broke (after I dropped it one too many times). So I bought a CTEK MXS10 charger. It is only 10 amps, but that is fine for my single battery. But it is a multi-stage intelligent charger and can handle AGM too (if I had them).
It seems happy to be plugged into the camper battery when I have hookup and doesn't get confused by the voltage drop caused by appliances coming on, unlike my last 'intelligent' charger which would decide the battery was dead, and go on strike.
Also, and this is where it is relavant to you, I have a battery buried under the step, but this charger comes with a quick-disconnect cable that you can permanently wire into the battery, but then disconnect the charger and plug in normal crocodile clips in order to charge other vehicles - i.e. I have not been forced to dedicate this charger to the camper only.
So what I have done is wire that quick-disconnect cable in so that when the floor of the wardrobe is back in place hiding the electrics below, it pokes out through a gap in that floor. I can then put the charger in the wardrobe and plug it into that cable. It also has a temperature sensor that you can wire permanently to your battery and that you plug in too.

Cheers,
Steve.