to Charge a battery...use a battery charger.
to "drive it around" puts a huge strain on your vehicle charging system which could cost hundreds to repair if it fails...a battery charger is under $50.
hook up the charger and let it go overnight.
best to remove batteries from the vehicle as when charging they may out gas hydrogen
so a well ventilated area.
once charged, take and have load tested at autozone for free.
a battery once fully discharged will loose some of it's ability to recharge to rating.
once that is settled, you can determine IF the battery charging system ( & disconnect) in your van is working...amd which position which switch is meant to be in.
On my 06 PW the disconnect is a disconnect to the battery- it is isolated, no power in or out.
and that is where I have the switch set for most storage periods.
even when isolated a battery may discharge on it's own- electrons will flow across the casing through damp dirt ...keep the battery clean
Mike