Bordon and Carole, I'm an avid lifetime boondocker. Where I camp there are never any hookups and I camp for months at a time. I have a generator
and have used it once just to try it out but found it noisy to use and fuel consumption was about a dollar or a little more per hour of use. Adds up and no ready supply in the back country!
Over the past forty years here is what I have found.
Flooded lead acid batteries work well and are probably your best value. They do require maintenance but properly cared for can last up to 10 years with minimal capacity losses.
AGM batteries have some advantage and can be used in different positions but I have found them to have a lower deliverable power content and a shorter life span.
Starting batteries are damaged and their life span reduced every time they are seriously discharged.
Deep cycle marine batteries are a compromise between the two and actually barely suitable for either application over the long term.
Deep cycle batteries are the only ones suitable for this application/ deep discharge.
No battery should ever be discharged below 50% capacity with the possible exception of lithium which also have cut off levels however I have yet to try this type.
Deep cycle batteries take a long time to charge and this isn't a reflection on the charger but rather the battery which will only accept a slow charge.
If you spend more than 2 or 3 days boondocking
per trip, battery power ISN"T likely to work for you. While you can minimize your power consumption you will likely have to carry multiple batteries which are heavy and need to be recharged when you get back.
Each discharge/recharge cycle ages your batteries even when properly maintained, in proportion to how far it is discharged.
I have found solar
to be a better way to go. I camp for months at a time with a single deep cycle battery and always have lots of power. It also seems to work well for the battery too as it has never been discharged more than 30% according to the gauge.
I started with 40 watts solar
which took all day to top up my battery and added additional panels until I got the power supply I wanted. I now have 5 and plenty of power for spring, summer and fall
camping but likely not winter. Actually, the cost of the five solar
panels was about the same as a good deep cycle battery.