what size wire

The amp rating sadly means diddly squat. It has only to do with heating of the wire, and you could for example run higher amps depending on cooling the wire.
What you have to consider is voltage drop!
Bruce, I would consider running two separate wires, 6ml minimum, one for the fridge and the other for your other outlets.
Also be carefull- some wires rate on overall size rather than copper conductor size. (plastic is cheaper than copper).

8 Guage is a decent size wire, I'd probally be happy with that. Personally I have 4guage going to the rear storage box to the third battery, then 8 guage to the inverter (mounted to the storage box) and two lot's of 6mm to the rear section where the Fridge, Water pump and 3 ciggy lighter plugs are (it's not far, probally only a meter or so from the 3rd battery).

Basically don't worry about wire rating (as said by Flash) cos it's all bull bleep . Just get the biggest thickest mother wire you can afford and is practicle to run through the car and go that way.

I'm not sure what type of inverter you are running, but they can draw some absolutally KILLER amps. Mines a 450w PureSinewave and from my calculations in can draw at least 45amps continuously at full load, that is hell of a lot of amps. Make sure you're wire is up to it. Also, peak loads on inverters need to be considered too.

If I were you I'd go at least the 8g for the inverter (basically car stereo amp power cable) and a couple of 6mm's for the rest, or run some 4g all the way (expensive).

Obviously I'm a little over kill, but I have mucked around with a huge amount of battery setups and wire configurations in the surf to try and handle all my toys and found that major overkill is the best way to go. You get stuff all voltage drop (you're batteries last longer while setup for camp) and when you add the next gaget (which you always will) you don't have to run more wires to the back.

I ran 8G also. Got it from DSE. Similar to the Jaycar cable that Sam used. I even run my compressor through it.

Leroy

Interested how to connect 8 gauge to a ciggy lighter. Did you use a step down piece of wire or some clever connectors.
SKinny

"Interested how to connect 8 gauge to a ciggy lighter. Did you use a step down piece of wire or some clever connectors. "

That's why I ran 6mm from storage box to the rear, just makes it simpler. The other way around it is to buy a 6 way fuse box (boat fuse box's are great). They have a bolt to attach a 4g or 8g crimp to, then have fused screw temrinals to run you're thinner wire to the different accessories.

That way you can have, ciggy lighter 1, 2, 3, and fridge plug, water pump etc etc or similar, all indivdually fused.

Maybe somthing like this, the 12 volt shop sells these:
<img src="http://members.westnet.com.au/themeads/pictures/host/fuse box.jpg"

Mighty nice , will have to look for one as well. Thanks

Skinny

there's terminal blocks from car stero places where you can connect your thick wire like 4g/8g and it has outlets for small wire.

Leroy

Okay, yesterday I went to my local Jaycar and picked up some quality looking wire (I thought!) to hook up my spotlights, it's Jaycar brand, rated at 25A and is 8 guage...cost $0.70 per metre. What would be the difference between this stuff and the $5-$6 gear you mentioned Alloy c/t? Appears to be a good quality multi-strand wire (quite flexible).

Gav

gav99x 70c per metre rated at 25amp and is 8 guage ,,,might be rated at 25amp max and they call it 8 guage but Iwill bet you that it is not 8mm squared in the actual wire ,, the $5/6 from 12volt shop is twin core tinned and 8mm sqared at the core ,not overall dia , whole point of the excersize in transfering power from under the bonnet to the rear is to NOT have any voltage drop ... how big a spotlights you planing on running with your" 25amp" wire ,,

Thanks alloy c/t. Sorry should have mentioned the cable is single core only, and not tinned. I've hooked up Narva blue Ultima 175's with it so far which are 100w globes and is seems to operate quite well. Am now hooking up 100w fog lights for those foggy country roads hence the extra wire purchase yesterday.

Excuse the ignorance with regards to the 8mm2 measurement, but is this a physical measurement i.e. 2.8mm x 2.8mm = 8mm2? If so this wire from Jaycar would be pretty close to that, about the same I'd say.

I've always bought tinned wire when installing 12V on my boat due to water/salt etc., is there a strong case for using it in vehicles also?

Thanks again

gav99x ,tinned = no chance of of copper verdigris so better long term conductivity ,applies = to boats and 4x4 .. 8 mm sq is the wire size with all insulation removed ,IE bare wire.,is also the perfect size fit for standard 50amp anderson plugs.

I got a techno chubby reading that.

Truckster , only trying to show that "wire aint wire " with apologies to Hoges "thats not 8mm wire ,now this is called 8mm wire" ..as I said earlier , do it right the first time so you wont be efed around later with " my fridge dont work right" and your young fellas "beer" [softdrink] is not to temp.

never thought to run the ground back to the battery. is this theory or does it make a difference to the voltage drop?

Conman ,no its not just a theory , vehicle makers try to save 1c here and 2c there and for costings sake use the vehicle body as the ground return on all non critical electrics , as an example just look at your headlights ,just upgrading the wiring from the factory fitted minimum will negate the need for spotties , try it youself ,run an extra neg wire straight from your h/light to the batt neg terminal ,you will see the light.

Dont really want to run it 'straight' to the battery , must have fuse on the posative.

From my second battery I have a terminal strip on the fire wall with allowance for 10 outputs , I use 5 , 1 of which is twin core wire that runs in flex conduit down the chassis rail to near the tow bar , it ends in a plug , I have made a fly lead with a cigarrette lighter socket which let me use a flouro light or frige outside ( a 12v tv , but dont tell anyone ) with the car locked up , good for when you leave camp with the fridge in the tent .

Glenn.

forgot to say am only running 6mm square , but not running much off it at once !

What if I ran seperate 6mm wires.

1 for each fridge plug, and 1 for the ciggy lighter plug and 1 for the inverter?

would that be sufficent? That way I have seperate circuits for each one if things go poo... ?

Thanks

Truckster ,why run 3 x 6mm ? , 1 x 8mm dual core is easier ,will do the job and the at the end you just run it into the fuse box that you "will use" for all the plugs down the rear end ,, ,,, I see that further down Crazie has got some stuff for you , 12v is not rocket science ,just a bit different to AC.

thought of the 3 seperate wires for seperate circuits...
so if anything goes pearshaped, I would still have power..

already talked to ads about it today.

Athol
what part of 2527 are you from. I just moved to the rainy gold coast after 8 yrs there

Steve

I measured the resistance in the body from the right rear to the battery in an NP Pajero - it was equivalent to 4Gauge wire ! So if you used 8Ga or 6Ga you would have MORE voltage drop than using the body.

In any modern car EVERY electrical device (except the Starter Motor) is earthed via the body - it WORKS.

If you really need to run an earth wire back to the Battery, at least earth it at the rear also to minimise voltage drop.

Mike

And so MikeDiD by you reconning just running a + wire from the batt and using the body as the earth is good enough ,,funny how copper is a better conductor tha steel ,ally ect ect , and EVERY 12v fridge manufacturer recommends a Direct connection to the battery ,, there is no way that a vehicle body with earth take offs all over the place is as effective as a straight to battery connection ,

Anyone who thinks my measurements are wrong can try it for themselves.

Mike

Well bring your paj around and we can try it with my multimeter ,OH I forgot ,Its a pajero thats made of this magic metal that conducts electricity better than any other vehicle ever built , better make sure you never drive in a thunder/lightning storm.

Posted my other answer before reading yours , this is my setup also.

V good cutout at rear of centre console !!

Although you dont need fuses on the return or neg wire !

Glenn.

call me back tart..