We do weekends and weeks out. 12v only. 4 x 110ah domestic batteries plus starter battery. 3 domestic would do. Fridge, LPG cooker, lights, tv and a couple of 12v sockets. Two solar panels keep the fridge running in summer and can keep the domestics at 100% in winter.
Was still a biggish installation with a lot of wiring, isolator switches, bus bars and fuse boxes.
You do need to study the BSS before you start as you will have a 4 year inspection.