The single stage controller/charger you currently have will probably take 2 to 3 times longer to charge a battery than a good multistage charger. That is 2 to 3 times the generator run time and fuel costs. Buy a good multistage controller/charger it will pay for itself before the winter is over with.
I also think a solar is a good idea. When you buy a replacement controller/charger I would check to see if it has capabilities to be used with solar panels.
Put skirting around the outside bottom of the trailer. It will pay for itself in warmth and propane saved. Some people just use straw bales others will tell you that straw bales will attract mice and be a fire hazard. Some others prefer foil backed Styrofoam or fiberglass panels.
