Let me add my $0.02 to the mix also. Good info from the other posters.
A Group 24 is a small battery for an electric only
refrigerator. A starting battery may only have 40 or 55 amp hour capacity.
Trillium installed a single Group 27, 105 amp hours on my 2005.
The NovaKool fridge draws 2.2 amps per hour if it is cooling continuously. A little math, 2.2 times 24 hours in a day equals 52.8 amp hours. It has a low voltage cut out (shut off) at 10.4 volts, so it will not kill a battery. The fridge will shut off for low voltage after about 12 hours of continuous running with out the battery being charged.
What other 12 volt items are you using at the same time?
Are you only putting already cold items in the fridge? Putting in warm items for the fridge to chill will take a lot of battery power.
Keep the frigde door closed. When necessary to get something from fridge, open door, get it, and close door.
As others have indicated, you have not provided the relevant capacity numbers from the battery. We need to know the battery amp hour rating. The important number for deep cycle use on a camper is Amp Hours (A/H).
I shortly had the battery rack converted to hold two Group 27s. Gives me a total of 210 amp hours, with 105 usable. The extra
weight on the tongue is not an issue for the frame or for inducing sway. The only issue would be the tongue capacity of the tow vehicle. Which by the way is ?
My Trillium came with a WFC 8712 converter distribution pannel. It is only a 12 amp charger. But it is a 3 stage intelligent charger, so is a good one for leaving trailer plugged in and shouldn't boil the batteries dry. Being a 12 amp charger doesn't mean it pushes 12 amps all the time. Battery charger logic is: when less than 13.2 volts is detected chager will start 4 hours of charge at 14.4 V. After 4 hours, charger will drop to 13.6 volts which is a slow charge. After 48 hours of no activity (which will not occur because of the
propane detector) the charger switches to maintenance mode of 13.2 volts. While in MX mode the charger will charge at 14.4 V for 10 minutes every 10 hours (stirs the acid and combats sulfation) and then resumes 13.2 V.
You will get much faster charging with a generator by using a good quality battery charger to charge the battery/ies. It won't hurt a group 24 or 27 to push 20 or 30 amps charge into it for a short period of time. You could safely set an intelligent charger for 30 amps and expect your battery to be 90 percent re-charged after only a couple hours.
You do not need a gel cell or AGM battery for use on the trailer tongue. A conventional deep cycle battery will work just fine and give better performance. Gel cell and AGM are mostly for special applications where the battery is not accessable or can't be in a vented location.
Before you buy another size battery or batteries, make sure you can get boxes for them and know how you will mount them. I went to a nearby welding shop and had a new tray built and mounted to the tongue.
Curt