Hi,
I think the butane stove is a good choice-- and (depending on model) it allows you to cook outside easily.
Your loads:
Fridge 42 amp-hrs
computer 15 amp-hrs (3 full charges of my laptop)
phones 6 amp-hrs (2 full charges)
LED lights 2 amp-hr (three LEDs at 4 watts for 2 hrs)
Pump 1 amp-hr (5 amps for 15 minutes)
Total 66 amp-hrs
The fridge 42 AH is based on a test I did on mine, which is an efficient 3 cubic ft - a Norcold NB751. Its about 2/3rd of your total.
If you add a furnace, the furnace blower might be another 15 amp-hrs on a cold day.
So, you need about 70 amp-hrs to go a full day without any charging from solar or running the van engine. If you go with the ground rule of not discharging below 50%, you would need a 140 amp-hr battery.
If you want to be able to go a full two days without any charging from van or solar, then you would be using 140 amp-hrs. In this kind of extreme case, I think it would be OK to discharge the battery to 20%, so you would need a 140/80% = 175 amp-hrs. Batteries will do hundreds of cycles to 20%, so doing it once in a while is not really an issue.
So, I think that the 155 AH battery you gave the link to would OK as long as you don't want to be able to go multiple days without recharging. On the plus side the single battery makes the system a tiny bit simpler and saves some space and about 30 lbs of weight. On the negative side (a pun

its one heavy battery (90 lbs) and its not going to be easy to move around, and, as RD points out, you could go with a couple AGM golf cart batteries and get 230 AH for about the same price. This would give you some reserve if you end up adding more loads later. I don't think you can really go far wrong either way.
I think RD in his post a couple weeks ago made a good case for 200 watts of solar being in the right area. The exception might be if you want to use the van in mid winter in northern climates routinely. Just to keep things simple, I'd go with Renology solar kit or package so that you don't have to worry about getting a compatible charge controller. I'd not worry about whether its MPPT (a bit more efficient) or PWM.
On the Romex, I used Romex for all my AC and DC loads, and if I were starting a new conversion tomorrow, I'd do the same. I like that it has the outer jacket for more protection against abrasion, and it bundles in a single jacket the wires for one circuit, and that its built to a spec that is pretty stringent (made to last the life of a home), and the solid wire bends into hooks that fasten securely to screw terminals without the use of failure prone press on terminals. Its also been used in all of the commercial RV's I've had before. I understand that there are qualified folks who feel there is a risk of vibration causing failures of solid wire. I've looked pretty hard for any cases of this actually happening and have not found any cases for RVs.
For me, the
#14 Romex works out well -- its big enough (15 amps) to handle all my regular AC and DC loads.
#12 would be fine also, but is a bit stiffer which makes it a little harder to route and hookup.
But, if you feel more comfortable using stranded wire, I'd be sure you get wire that is built to a spec that makes sense for the RV environment. Getting your wire from a place like BlueSea would be good as most of their stuff is made for the marine environment, or buy something like the SJT spec wire from Lowes off their reel. If the wire you are looking at does not have the spec its made to stenciled on the wire, I'd not use it as you have no idea how the insulation will hold up over the years.
I don't use chassis grounds to complete the negative side of the circuit on any of my loads -- I run a full size negative and positive wire (mostly the Romex). To me, this just seems like less work and more reliability. You can do a good job with chassis grounds and may not have any problem with them, but I've spent too much time trying to find electrical problems in old (and sometimes new) cars that turned out to be bad grounds to want to go through that again. I do have a chassis ground from the negative terminal of the house battery to the chassis -- this is a safety ground to make sure the chassis cannot go hot due to a short somewhere without blowing a fuse. Also, when you are hooking up the inverter, I'd follow the advice in their manual to the letter -- including on grounds.
I like the inverter/charger as it makes wiring simpler and takes care of the automatic change over from house battery power to shore power. If I were doing mine again, I'd probably go with a pure sine wave inverter.
One thing to keep in mind when considering these varying opinions is that you probably can't go wrong either way, so, I'd not agonize too much over which way to go -- just flip a coin
Gary
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