How many batteries do I need?

The number of batteries needed for RV boondocking depends on how much draw you'll be pulling.
Your battery bank should also reflect your solar array with at least as many amp hours in your battery bank as there are watts in your solar array. But, if you're using lithium batteries, you can drain them almost twice as deeply and therefore only need a little more than 1/2 as many amp hours of lithium battery power as you have watts in your solar array.

Incredibly conservative RVers will want at least a 200Ah battery bank. This will power the appliances running propane and minimal lighting. Beyond that depends on what else you'll be running. The average installs we do are 400-800 watts. Power hungry RVers will have north of 800 watts of solar panels! When starting to use your new solar system, before you know your actual usage, it is good to keep a close eye on the voltage of your battery bank to confirm it will meet your needs and prevent from draining it too low and then expand your battery bank/solar array if necessary.