I have owned my travel trailer for about 6 years now and (gasp) have never camped off the grid… until now. I have a trip planned that does not have access to electricity and my battery is shot. ...
I'd get two 6V's from Sams club or Costco unless you can get a deal on Trojans somewhere. I bought two from Sams a couple of years ago and it was around $190 out the door, core and tax included. The 6V's will be the most power for the money and will take some rough treatment.
If you're going to be Festing continually, I'd suggest to look into solar. It is quiet, easier, and you don't need any fuel. You can take your genset along but if the sun shines, you may not need it.