Upgrade: Rear power socket

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just out of interest, that cable is way over rated for a 4amp fridge.

Cable rating is the current a cable can draw at its maximum temperature. Cable temps are rated such as V75 (75 deg C) e.g. a 6mm flexible single core cable can deliver 56amp but will be 75 degrees to touch.

the voltage drop reduces as the load decreases. What im trying to say is their is going to be very very little difference in voltage drop with a 4amp load on a 6mm cable compared to a 2.5mm cable.

If anyone wants a table of current carrying capacities i can dig it up...

[prado-admin Senior Member Find all posts View Profile Close prado-admin]

Hi Andrew,

So what cable do you suggest I use? The only other one Jaycar has is significantly thinner.

This is what I was going to use:
Black 8GA OFC High Current Power Cable

Will this do the job having a few accessories and the fridge?
25 AMP DC AUTO POWER CABLE

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will let you know tommorrow

I am going to bench test several sizes with a 4A load and see what the voltage drop is over 100m....

Personally i think 2.5mm Flex would be ample (25A) but will confirm tommorrow. (the cheaper of the 2)

Would definatly run seperate runs to the fridge and accessories and have seperate fuses as well.

That way if your handheld fluro goes out it doesnt take the fridge out as well

6mm for car audio amps yes, they peak at VERY high currents. Usually higher than the fuse rating... but a fridge nah doesnt matter.... slight rise in start up current then constant...

can anyone tell me the start current of a engel?

[Drew Advanced Member Find all posts View Profile Close Drew]

oh and 6mm cable is 6mm Cross Sectional Area of the conductor, not diameter....

You may find this is incorrect. 6mm automotive cable, as it is generically referred to, has a cross sectional area of 4.59mm² (well the decent quality stuff anyway). As stated earlier, the "6mm" loosely refers to the diameter of the wire.

There are so many different types of nomenclature when it comes to wiring, automotive vs mains vs aviation and so on. It's something I've had to wrestle with every day for years! (No wonder I'm going bald).

Andrew, there are established formulae for calculating the voltage drop in cables, it takes into account the resistance of copper per metre and the cross sectional area of the wire. It's very important to use the CSA in this calulation rather than the diameter (the error will be obvious).

As for the temperature ratings you were referring to, you might find that the figures you were quoting were the temperature ratings of the insulation before it starts to soften, not the temperature the cable will get to when loaded to it's maximum current (although on cheaper cables these figures might be very close). These figures are used when calculating loom currents and temperatures as an adjacent conductor can get warm and heat up another conductor that may not be carrying it's full capacity.

I use 6mm auto for jobs like you are all mentioning, At 4.59mm² it keeps voltage drop to a bare minimum and has plenty of head room for fridge starting currents and the like. The drawback is that it is expensive (quality stuff) and it's a bit bulky and sometimes hard to route in a smaller vehicle.

Good luck with the wiring job, I'm about to wire up an auxillary feed to my camper trailer and also the brake wiring, should be fun! :-)

Cheers,

Drew.

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drew
I am aware of the voltage drop formulas. I am a industrial electrician by trade. But for this forum what i've covered is ample...
Wasnt aware of the bizzario automotive cable size though, i use aflex for everything....

With mains stuff anyway, the insulation and the way its installed has a dramatic effect on max loading

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just had a though, your talking 6AWG right? American wire gauge? not 6mm sq

[Drew Advanced Member Find all posts View Profile Close Drew]

just had a though, your talking 6AWG right? American wire gauge? not 6mm sq

Sorry I took a while getting back to this one, work has been insane this week - upcoming exams at college - the missus is sick and we are having problems with our first child on the way - and I've been working on the Prado and 4WDing so that has left little time for much else. (This is why I'm posting this at 1am after I got home from work :!: )

See these images:




These are the sort of wire I was referring to. As with many things electrical, there are number of different nomenclature systems, I work on aerospace stuff and most everything is in AWG, but the mains stuff I do is in mm^2 but automotive seems to be in mm diameter. :roll:

Oh well, better go to bed. I'll post some pictures of my wiring job on the Prado when I get time.

drew.

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as you said

6mm auto = 4.58 mm'2
4mm auto = 1.84 mm'2

wonder how they work that out? Its not really linear in the sizing is it...

[Brucey Lurker Find all posts View Profile Close Brucey]

A friend of mine put me on to this link regarding cable sizing, and carefully choosing the right one.

http://www.fridge-and-solar.net/wire.html

The quote comes from a book by Collyn Rivers, which has a lot of info on camper trailers etc. and I'd recommend it. Before I got the Prado, I got the trusty Commodore wired up back to the trailer to run the fridge, so voltage drop was a concern.

I'm not going to hesitate with going the 6mm to ensure the fridge keeps going as long as possible before under voltage cuts in...

Bruce

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Re: Upgrade: Rear power socket

4mm will be sweet for 10amp supply at 10m length . its only going to be 3-4m from the battery to socket if in car .

[plucker Advanced Member Find all posts View Profile Close plucker]

For the few extra bucks the bigger cable will cause less headaches and run the fridge slightly longer.

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For the few extra bucks the bigger cable will cause less headaches and run the fridge slightly longer.

Exactly , bigger the better , but watch your fuse size . Waecos and Engels draw around 7-8amps max on a warm start-up freeze , they run at about 2-3 amps normal , the bigger the fuse you install , the bigger the fault current , thus damaging the applaince more ....in this case blowing the fridge rather than resetting the overload.

BTW this is only if you are running a fridge from the wiring , some poeple connect a rear winch (my mate) and camper/caravan to the aux battery supply.