Thread: rewire aux socket to 2nd battery

I have recently installed a 2nd battery and controller. I have put in a new 6-way blade fuse block and have started to migrate accessories like UHF & GPS onto it.
I want to rewire the rear aux socket and front cigar socket to the 2nd battery (off the main).
I have the circuit diags off the RAVE CD, so know that aux socket is fuse 32 in the front fuse bank. Which is the plug socket and/or wire at the rear of the fuse bank that comes in from the rear. I know the colour of the wire (green/purple) - but cant be sure where it enters the fuse box.I want to cut this and rewire it to the new 6-way blade fuse box off the 2nd battery.
I dont really want to run a new wire to the rear, the original is 25A anyway so is more than adequate for a fridge.
Anyone done this before?

My first post on here so hi from the UK, great site and some cracking Disco's

Having looked at the wiring diagrams I think this is the situation:

First off the fuse that supplies the cigar lighter socket (F15) also supplies several other items, amongst them the BCU, and is monitored by the IDM (Inteligent Driver Module). The wire that comes from C0587 feeds a header that supplies all these items, except the IDM which is integral to the fuse box. Therefore it is highly likely that back feeding the cigar lighter with a voltage will confuse the BCU or IDM and prevent correct operation of the central locking and/or alarm system even when disconnected from the fuse box since the BCU is still connected to the cigar lighter.

If you want to feed the cigar lighter socket from an aux battery then you'll have to disconnect it further up the loom at header C0291 pin 12, which is buried under the dash in the passenger footwell. I'd suggest that UP's option of fitting a new socket will be the easiest and will also give the option of an ignition switched socket as well as a permanently live one.

Secondly, the rear accesory socket (a) doesn't get monitored so should be fine but (b) whilst it is rated at 20 A (IIRC) the wire that feeds it is quite long and has a significant voltage drop on it. If your load is more than around 5 A (and certainly if it's 10 A or more) and has an undervoltage shut off system you may find you cannot get as much run time as you expect. I would suggest running a much thicker gauge cable to the back to minimise voltage drop. I tried an absorption fridge on mine, that drew around 13 A and would shut off after only a few minutes when the engine was switched off. The socket in my D2 is supplied from the standard LR battery (no aux battery on mine) and the fridge shut down voltage is around 10.5 V. A compressor type fridge (Engel/ARB etc.) obviously draws considerably less, but still worth checking the drop.

Cheers,
Anthony.