Next to the fridge, in the right side, I've found this thing, it has two wires, a red and a black one, I think they came from the second battery installed under the co-driver's seat. It has also a "potentiometer" You can set it on 0.5, 1.0, 1.5 and 2.0 positions... It has a fuse and 250D wrote on it. Next to that fuse it has a switch "ein" "aus"...
I was thinking that thing is to charge the batteries while the van is connected to 220V/240Volts... but the potentiometer makes me

Could be?
Some pics of it here:
http://www.flickr.com/photos/11894776@N ... 154016641/