Yes,
Like I stated in a previous post, calculate need. It is not difficult to estimate, however there are multiple factors that affect battery performance (temperature, age, cycles between charges) that I am not that vested into and "getting close" was my goal.. Figure what you are going to run when off the grid. Check all appliances, fans, etc. amps, calculate how often it will run during the time your are camping to compute amp hours (Ah), add it up. That is your need. I add in 1-2% for vampire draw (power drawn when appliances/devices are off). If you can't get the info off the actual device amps, check RV blogs, lots of research out there. Than find a battery setup to match it up. My biggest challenge was batteries are listed in RC or Ah. Reserve Capacity (RC) is the number of minutes a fully charged battery at 80°F will discharge 25 amps until the battery drops below 10.5 volts. An amp hour (AH) is a rating usually found on deep cycle batteries. The standard rating is an amp rating taken for 20 hours. Than figure the depth of discharge, that is how far you drain the battery based on type. The rough numbers I found are 50% for traditional flooded lead acid, 80% for sealed AGM and, well around 100% for Lithium Ion. That was the biggest surprise for me was having to cut my capacity in half with a flooded lead acid battery. Guess that is why everyone is willing to shell out $900 for a Lithium Ion battery. We dry camp only 1-2 nights, run onboard gen during the day or drive 6-7 hours and I added to extra Ah assuming I wont fully charge during driving. One could figure that out, but again, I'm just trying to get close. Anyways, my number figured in a cold fall night so run furnace 15-20 min all night and my number is 220 Ah. I bought two 235Ah 6v golf cart batteries. that is 235Ah at 12 v.