Fair enough, but my point is that a Grp31 battery on its own will power everything including a fridge for 2 days minimum. So unless you are doing trips where you are parked for long periods at a time, a single grp31 would serve most people very well. Add the solar panel to that, and even if not in full sun you add time to your ability to stay stationary. The jump pack you mention above is a really nice inexpensive backup.
The dual battery setup has become this ubiquitous over-landing setup that all the new folks jump right into one without considering their needs. I'm just here to encourage folks to think about the kind of trips they do before deciding that the added weight, expense and complexity of a dual battery setup is a "necessity" to go camping.
I'll stop muddling up your build thread now!
This is not my first build and, being I have been wheeling off and on for about 20 years, I would not consider myself "new folks". I understand you are trying to "encourage" but continually questioning my build an encouragement. I agree, most people do not NEED dual batteries. Nor do then NEED lockers, a winch, roof lights, or an on board refrigerator. We have all these items for convenience, and to be better prepared for the unknown. I live in Minnesota, do a lot of camping in the woods, mountains out west, and yes, the vehicle can be sitting for upwards of 10 days. At an additional cost of under $50 total, I will add dual batteries and know I have the additional capacity. When rolling through Moab, I won't need it. While sitting in deer camp in early November, using the roof lights every evening, and likely not driving the vehicle during the entire trip, I will be glad I have it.
My assessment of my current needs, future plans, and low dollar impact makes the install an easy choice. You do not have to agree but that is the route I am going. Thanks for respecting my decision.