Russel & Mary replied:

Skinny, I too am confused with mm2 automotive wire and how they work it out. I think that auto wire that's about 5 mm DIAMETER when the insulation is off should be about right. Rus.

Skinny replied:

Thanks Rus, I am still looking. When I buy some it seems much cheaper to buy a roll. If anyone else would like some we could split a roll, whenI get the size. I think 8gauge is what they reackon can anyone confirm this.

Skinny

Wizard1 replied:

I need to re-wire an Anderson plug on my caravan. So I wnet to an auto electrician told him what I wanted to do he gave me the correct wire (80 amp I think it is). Up until that point I had wasted time at Repco etc.

Need a bus bar, I called the auto electrician had exactly what I needed.

JohnN replied:

Here is a table that may help

Site Link

cheers
John

Member - Bradley replied:

8b&s would be 8 guage battery and starter cable for my guess.

any car audio store (jaycar / jb hifi / autobarn etc etc) will have 8 guage power and earth wire on bulk roll, buy by the metre. They will also have all the connectors and fuses etc.

But 8 guage would be almost overkill, you could get away with running 10 guage wire.

davidta replied:

Hi

B & S is Brown & Sharp.
It is also known as the American Wire Gauge or AWG.
There is also SWG or Standard Wire Gauge, which is different to the above.

Hope that helps

blown4by replied:

3mm, 4mm, 5mm etc refers to the cross sectional area not the diameter as it is actually measured in mm squared or square mm (sorry I can't do a little 2). I would think 5mm would do fine, about the same as you would use for your driving lamps and is probably heavier than what your vehicle uses on the alternator output.

Old Scalyback & denny replied:

6mm twin red and black buy it from most car accessoriy stores is plenty big enough to run a fridge get the twin so that you run both positive and negative back to the battery get a good plug and plug top i use the 32v T type myself never a problem

steve
ps dont get battery cable for a fridge you will never get a plug to fit properly

Derek from Affordable Batteries & Radiators replied:

Hi Skinny

I supply 6mm2 tinned solar cable for fridge applications. 0.05 voltage drop over 6m. (Sold per meter)

It will fit the large yellow lugs if you are neat with removing the insulation and best to use a auto reset breaker around 20 amps to prevent voltage drop.

It is available at me of course ABR and also at springers, whitworth marine and bias boating. Repco only sell 4.8mm2 which is non tinned and not the best current carrying wire.



Regards Derek.

Geoff M (Newcastle, NSW) replied:

Skinny,
If you talk to an Auto Electrician they'll measure a cables overall diameter in millimetre's including the insulation or they'll measure the diameter of the conductor in Brown & Sharp Gauge (B&S) which is the same as American Wire Gauge (AWG)

If you talk to me or any other person with a mainstream electrical or electrical engineering background we'll measure the cross sectional area of only the conductor in square millimetres. The conductors are the only part of the cable that does the work.

For me, measuring the overall diameter of a cable including the insulation is about as relevant to its current carrying capacity as measuring the diameter of a stick to determine how much heat it will produce on a fire!
The insulation thickness from manufacturer to manufacturer is just too variable. Eg, Brand A and Brand B may both measure out at 5mm in diameter. Brand A's conductor may be 3mm diameter with an overall coverage of 1mm of insulation whilst Brand B's conductor may be 2.5mm diameter with an overall coverage of 1.25mm of insulation. Same accurate cable description, two significantly different current carrying capacities!!

For current carrying capacity of a cable used in extra low voltage installations (Extra Low Voltage for the purposes of our vehicle needs can be defined as below say about 48 Volts DC) quite a few factors need to be included,

1 - Cross Sectional Area of the conductor in square millimetres or diameter of the conductor in millimetres or diameter of the conductor in B&S or diameter of the conductor in AWG, all of them really must exclude the insulation.
2 - Number of individual strands in the conductors. The more the individual strands and the smaller their diameter the less the losses in the cable, the less the losses the better.
3 - Total length of the circuit including the negative leg for voltage drop calculations.
4 - Maximum expected current drawn by the load on the circuit.
5 - Maximum tolerable voltage drop at the load.

For practical purposes number 2 can be ignored if we use off the shelf multi-stranded cables. All of the other points really should be factored into a calculation!

Having said all that I use the same cable Derek from ABR lists above. I bought it from BIAS Boating in Newcastle. It actually does satisfy all of my points listed above for a load up to about 8 to 10 Amps and a circuit length of about 10 metres in total. (5 metres positive and 5 metres negative) I always wire back to the battery negative, never to the vehicle body or chassis. Note: I only calculated for 8 to 10 Amps when I worked mine out.

Geoff.