RE: Using an inverter to power lights, etc inside the van
I've talked about this before but will hit the subject again.
With a little hunting (very little in many cases) you can find 12v DC
accessories for your van, things like lighting especially, incandescent,
fluorescent, or LED.  Also fans, laptop power adapters, etc.  This avoids
the inefficiency of using an inverter to provide 110v AC.  The power draw
from your battery will ALWAYS be higher through an inverter than to power a
12v appliance directly.  And unless you buy one of the very expensive pure
sine wave inverters you will find that many power tools or appliances do not
run as well off your inverter.  If it is difficult or impossible to get 110v
AC then power tools run off the inverter will work but not as well.   That's
where the cordless/battery powered tools come in very handy. And most laptop
power supplies that run off 110v AC are actually putting out about 19v DC to
the computer.  It is a very inefficient process to jump the 12v DC from  the
battery up to 110v AC and then back down to the 19 v DC the computer is
looking for.  And 12v adapters for laptops can be had for from $20 to $50
(usually much more if ordered from the laptop maker) and do the job without
the loss through the inverter.
YMMV