Batteries are used extensively for boondocking
as a major power source. If you have access to shore power, they are a backup.
Add up your anticipated power consumption for a 24 hour period. Include things like your fridge
, gas detectors, lights
etc. As an example, a device that uses 2 amps per hour will consume 6 amps in 3 hours and 48 amps per day. Multiply this number by the number of days you intend to camp. This is your total consumption. Double this number to get the minimum battery capacity you need. Personally, I multiply this number by four.
You will need one or more deep cycle batteries. Starting (automotive) batteries are damaged by repeated discharges and usually not suitable for this use. Lead acid batteries are the most common and come in several formats like flooded, AGM etc. Lithium batteries which have a greater energy density and can be more deeply discharged are more expensive but gaining popularity. Careful not to discharge batteries beyond manufacturer's recommendations.
can be used to power your trailer/charge your batteries but fuel costs can add up. I find solar
panels much better, I camp for months with a single battery and have lots of power.