Our approach was to make sure our elec needs were minimal - an Iceco JP50 fridge, draws 32w when running, which is only 20% of the time, and some charging needs, and a couple of LED lights. We have done multiple week trips in both hot and cold weather with only a Bluetti EB150 (1500 watthours storage) for battery storage. It alone will run the fridge for 5 days. No problem with outside temps down to 10 at night, inside not much above the couple nights we stayed in hotels, and I just avoided using the Bluetti until after we were driving the next day and the van had warmed up - no need to power up the fridge, it was plenty cold already! $50 inverter under the drivers seat, cabled to the battery (inverter has its own fuses), and we use that to recharge the Bluetti every couple of days when driving with the regular 110v wall charger for the Bluetti. No solar panels needed, no wiring complexity, interconnect, charge controllers etc. Easy. One self contained unit for $1000 has the battery, charger, charge controller, inverter, AC, DC and USB output, with peak power of 1500w. And yeah, it’s LiFePo4, so you get to use 1470 of the 1500 watts stored in there, at constant voltage. The old lead acids drop voltage with every electron you take out, and by the time they get down to 10.5v or so, having used 15% of nominal capacity, your fridge and everything else will shut off. No matter what config you use, standalone Li batteries, or a self contained like Bluetti, go lithium. Oh, and Bluetti is 50% the cost per stored watt compared w Jackery or Dometic. and I can pull it out of the van in 2 minutes for use in the house during an outage, to do construction away from power, or take it into the woods to run amplifiers for music or whatever. Works for us. Just sayin.