Solar isn't mandatory. Here are some cases where it might not be worth the trouble:
The rest of this document assumes the camper is equipped with normal lead-chemistry batteries (flooded, AGM, etc).
Solar is incredibly useful for nomads with lead-chemistry batteries. There should be a good reason why they would plan a build without some solar. Even just a small amount. Some reminders:
For whatever reason you are not going to have any solar in your build. So how will you charge your batteries?
[note: this section is based on a reddit post]
An isolator will do the heavy lifting, but is unlikely to get/keep the house battery fully charged snce the voltage isn't high enough.
There are a couple of ways around the low voltage issue:
Like alternators, generators have a lot of current on tap. But as with alternators you have to run them a long time to get a full charge. Deep cycled lead-acid batteries require hours of charging at Absorption voltage to get fully charged. The most efficient time to run the generator is when the batteries are deeply discharged (early morning).
If you are staying at campsites with power you can just plug in and let your converter handle loads and charging. You could skip a day or two and get back on the charger without causing too much damage.