Any good three stage charger will bulk charge fairly fast. Check to see what you have before spending and cash for a new one.
I installed this on my old pace arrow with a 2 golfcart battery house bank.
Progressive Dynamics 9160A with a Charge Wizard.
http://www.progressivedyn.com/rv_converter_pd9170_2.html
http://www.progressivedyn.com/charge_wizard_9105.html
or larger if you plan to increase the battery bank to larger than 2 batteries (12v parallel or 6v series which I'd recommend.)
None of the 12v side is going to help much with the heat down here in the south during the summer. In less than 90 degree heat I would consider installing a fantastic fan w thermostat in the bathroom and open a cross flow window. With water available and some moving air most dogs can tolerate the heat fairly well. You would need to try it a time or two with a thermometer that records highs before putting the animals into the mix.
For the really hot season electrics or generator use is gonna be mandatory with the genny being the more expensive route.
I would upgrade the converter and battery first. Adding either a similar 12v house battery as you have or two new 6v golf cart batts.
Second I would upgrade the house ventilation with one or two fantastic fans.
Both are fairly easy upgrades and will minimize the run time on the generator and or the need to run it for recharging from heat/ventilation use.
Good Luck and let us know how it turns out.
Les
