Considering that it is for a van...first get one or two batteries. If two then 100
ah will do, or if one then get at least 160ah. If you plan to get solar panels that are more than 12v then get the mppt controller, if just 12v then get a pmw controller and whichever get at least 30
amp so you can expand your system. 6v batteries are great but sometimes overkill.
they will last through a lot more recharges, but you do have to get 2. Once your batteries are in place you can consider solar panels. Windy Nation does not have the best prices from what I've seen. Look on
amazon or go to Renogy.com Do you have space for 2 batteries, that is your first question?