auxiliary batteries

Here's a picture of my battery and refrigerator setup in the back of my van. 2x130AH AGM, Redarc BCDC1240 connected to the 'Analog' panel feed under the passengers seat. The Engel 39l fridgeis around 25 years old. The batteries are covered by a carpeted panel so are secure and hidden. It may...

Hello I want to enquire if anyone could confirm for me if selecting the second battery option on extras list when ordering a new van, is this in fact a leisure battery with a split charger that can be used when ignition is turned off to be used for running battery operated items when camped etc...

I'm looking to run a cable from the main battery into the cabin. Anyone know if there is an easy route through, maybe using an existing path, or do I have to think about drilling a new hole in the engine bay bulkhead (gulp). Any advice much appreciated.

While I save alittle more for the install, I am looking to source advise on pros/cons and links to house the 110ah battery under vehicle. I do not have room under the front seats and due to changable internal use, no room to the rear. Thanks. @travelvolts

there's a thick cable under the passenger seat that I'm wondering what it is. It has a barcode on it? so it looks original. I'm fitting a leisure battery /ctek solar charger - so am hoping it could be useful. Guy