camping in public campground no hookups

We "dry camp" (no electric or water hookup) all the time using one 12v battery for 2-4 days. As everyone says, just restrict what you use in the camper - no lights unless needed, leave water pump off until needed, etc. A vent fan will use much more electricity than you think - try not to use it unless needed, and only for as long as needed. Leaving it on overnight will drain a battery. When you dry camp I would suggest looking for shady campsites where you won't need a vent fan.

Have fun! It is very much doable and fun for everyone. You will probably run out of water long before your battery drains!