With my Westy hooked up to shore power, I have two Schmaker 1.5 amp smart
chargers under the sink. They are connected to the start battery and the
other is connected to my aux battery bank (4 batteries). They are in place
year round but unplugged during the summer months as my solar takes over.
There are several brands that do the same thing, maybe check out a
Batteries Plus store and see what they offerm I picked mine up at walmart
for about $20 each.

Tim