aux battery utilising the rear cig lighter wiring
 

Hi,

I have a 2000 grand voyager 2.5 td se and have noticed the rear cig lighter is always powered. I've also noticed its rated for 20amps.

As I these voyagers seem to have more than most cars in the way of electrical power demands and as I often camp or even use an inverter in the car I was thinking of adding an aux 12v 50amp (ish) leisure (or leadacid) battery in the boot as a permanent fixture.

I appreciate I'll need to rig the wiring under the bonnet so the rear cig socket and battery are disconnected while the engine turns over, however I was wondering if I need to consider any kind of amp regulator on the rear battery, as if I something like that I suspect it will be difficult to implement as power could potentially flow both ways between the front/rear batteries.

As the existing wiring for the rear cig lighter much be capable of carrying 20amps and be fused as such I wonder if I'll get away with only ensuring the rear battery is disconnected while the engine is starting?

I'd suspect the length of the wire would also cause sufficient voltage drop to help limit the amps going along it?

Anyone done this before?

Thanks in advance

Jon

sorry about the numerous typos, I'm typing in a rush :-) In the third paragraph I meant only disconnect the rear battery while the engine is starting thus prevent excessive amps being drawn across the wire for the starter motor.