Anderson plug and wiring

Submitted: Monday, Jun 18, 2007 at 14:11

The Birds (WA)

Currently getting my camper trailer built and the wiring is being done as we speak.

A friend of mine was telling me to make sure that the wiring from the 50amp Anderson Plug is a suitable size for charging the third battery on the CT. Due to the length of cable from the front battery to the one charging on the CT, he reckons the third battery wont charge as quick as the front one.

The camper trailer sparkie has put in 6mm cable from the Anderson Plug. Any real advantage in upgrading to say....10mm ??

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AnswerID: 247660   Submitted: Monday, Jun 18, 2007 at 14:15

GoneTroppo Member (FNQ) replied:

I've been looking at the same thing. My slide on Camper is 6mm from the Anderson Plug to the AGM

The answer seems to be here

I'm off to upgrade my wiring.

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FollowupID: 508588   Submitted: Monday, Jun 18, 2007 at 21:57

The Birds (WA) posted:

Thanks Gone Troppo.

Finally got a chance to read all the info on the site and I must say I found it very informative. Along with that info and advise given below it has helped me make my decision. I will be going for the 6B&S option.

Thanks heaps
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AnswerID: 247678   Submitted: Monday, Jun 18, 2007 at 16:08

Robin Miller replied:

Hi Birds

I say he has probably guarranteed that it won't charge as quickly with 6mm cable which I consider undersized.

10mm is a non standard size but I'd go to 8mm sq minimum.

You also need adequate wiring in the car side to , also 8mm sq min.

If you have heavy loads , then 15mm sq might be worthwhile however it gets
a little hard to work with and would require bigger Anderson plugs as well.

Robin Miller
Robin Miller
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AnswerID: 247679   Submitted: Monday, Jun 18, 2007 at 16:10

kcandco replied:

Hi Birdy You might find this site interesting reading also.

regards KC
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Reply 3 of 7
AnswerID: 247688   Submitted: Monday, Jun 18, 2007 at 17:15

Member - Mike DID replied:

Cable sizing is really confusing.

8 Ga cable is 8.4 sqmm (4mm dia) and has a 6mm diameter over the insulation and will have voltage drop of 0.36 volt at 24amps over 3 metres (supply and return). It can carry 55 amps max.

4 Ga cable is 21 sqmm (6.5mm dia) and has an 11mm diameter over the insulation and will have voltage drop of 0.36 volt at 60amps over 3 metres (supply and return). It can carry 100 amps max.

The outside diameter is a poor indicator - unscrupulous manufacturers put thick insulation and thin copper to save money.
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AnswerID: 247700   Submitted: Monday, Jun 18, 2007 at 17:49

The Birds (WA) replied:

Thanks for the info and respones - it is sincerely appreciated.

In light of the responses, still not sure what cable should I specify to the sparky from the Anderson plug (50amp) to my battery box which will have a 100 amp battery. Also from the Anderson plug to the front battery.

Thanks again
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FollowupID: 508514   Submitted: Monday, Jun 18, 2007 at 17:54

Member - Mike DID posted:

Will you have a fridge running in the trailer while you are driving - how much current does it draw ?
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FollowupID: 508527   Submitted: Monday, Jun 18, 2007 at 18:24

Batboy posted:

I suggest you ask him to double up. Run another 6mm2 cable along with the first at least you know he has this cable on hand. It is what I have done and seem to work well. You will then have 12mm2
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FollowupID: 508537   Submitted: Monday, Jun 18, 2007 at 19:25

drivesafe posted:

Hi Birds, 6mm cable would be next to useless, standard 50 amp Anderson plugs can accommodate cable up to 16mm2 and either this or 6 B&S ( 13.5mm2 ) would be recommended.

You will still get a voltage drop but these two cable sizes are both commonly available and are about the minimum size you want to fit if you want to get reasonable charging of your rear battery.

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FollowupID: 508554   Submitted: Monday, Jun 18, 2007 at 20:12

The Birds (WA) posted:

Hi MikeDID,

Yep will have a 50ltr Waeco running in the camper trailer and a couple of flouros. The flouros are drawing about 0.5 amps/hr and the fridge 'apparently' uses 0.86 amps/hr. The auxiliary battery in the 4wd and in the camper trailer will probably be a 115amp Trojan deep cycles or the gel type. Still have to work that part out !. Only other loads will be laptop/phone/dvd player charging, which hopefully will be done whilst driving as we are driving around Oz. May end up getting another small fridge to run off 12 volt.

Gday Batboy - double 6mm run sounds good however if I have the chance to change the wire to 6 B&S would that be better ?


My mate basically told me that the 6mm is probably pretty useless aswell. From a internet link provided in an earlier reply also recommends the 6 (B&S) . Seems like this could be the go. What does the B&S stand for ?? Also would I run thsi same cable on the vehicle ??

Thanks kindly again for the helpfull replies.


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FollowupID: 508569   Submitted: Monday, Jun 18, 2007 at 21:02

drivesafe posted:

Hi again Bird, B&S stands for Brown & Sharp and was the cable gauging standard used before AWG ( American Wire Gauge ) was introduced.

Both B&S and AWG are the same size and are also simply known a s the cable Gauge or G, in other words, a cable could be marked in any of three Gauging type but be the same such as 6B&S, 6 AWG and 6G and the cable would be the same size ( 13.5mm2 ).

It may seem a bit confusing ( and it is ) but if you need to order cable, try to get it as B&S as this is a fairly commonly used size system or ask for the cable in square mm which is marked as above with the 6B&S, 13.5mm2. This mm2 is the cross sectional area of the actual copper in the cable.

To add to the confusion, here in Australia ( Britain ) there is also a cable sizing system marked with Auto or Automotive cable, for example, the cable mentioned above in your first post was referring to 6mm, which is a shortened way of stating 6mm Automotive cable.

Any cable with an Automotive size marked on it and no other cable size given, take care as the is no real defined size in this marking system as the Auto measurement is the total width of the cable including it’s plastic insulation.

Your 6mm is actually only somewhere about 4.5mm2, depending on what company made the cable.

Now your really confused and just to make it more confusing, when using the B&S sizing, the higher the number the thinner the wire. That makes sense doesn’t it, NOT.

Here is a basic list of commonly used sizes set out from thinnest to thickest and hopefully will help you pick cable sizes that you require.

4mm Auto = 1.85mm2 or there abouts

5mm Auto = 2.9mm2 or there abouts

6mm Auto = 4.58mm2 or there abouts

8B&S = 7.9mm2


6B&S = 13.5mm2


4B&S = 21.5mm2

2B&S = 33.6mm2

With the exception of the 10mm2 and the 16mm2, all these sizes may vary slightly from one cable brand to another.

Cheers and i hope this hasn’t muddied the water too much.
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FollowupID: 508573   Submitted: Monday, Jun 18, 2007 at 21:07

drivesafe posted:

Sorry Bird, I forgot to answer your last question.

If you get the chance, I would definitely run the heavier cable all the way through your vehicle.

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FollowupID: 508582   Submitted: Monday, Jun 18, 2007 at 21:42

The Birds (WA) posted:

Wow drivesafe what an answer !

Yes it does seem to get quite confusing, however you did do a great job of explaining it all. I think I will go for the 6B&S for the vehicle and camper trailer as it appears it should do the job a lot better than the propsed 6mm wire of which I have no specs or info on. Is the 50 amp anderson plug sufficient ? Seems to be a common size so one would hope it is ok ??

Thanks again.........
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FollowupID: 508590   Submitted: Monday, Jun 18, 2007 at 22:04

The Birds (WA) posted:

Drivesafe - the website provided by Gone Troppo actually changed my thoughts on the Trojan batteries and think I will go for the AGM as it seems they will suit my needs better. The only real drawback seems to be price, however even though they seem to cost more initially it appears they may actually last longer.

Thanks i have learnt a lot .

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FollowupID: 508594   Submitted: Monday, Jun 18, 2007 at 22:39

drivesafe posted:

Hi again Bird, 50 amp Anderson plugs are now days the industry standard for connecting battery power between the tow vehicle and a caravan or camper trailer.

BATTERIES, this is always a hotly debated subject but it still comes down to something your have already posted, pick the battery that best suits your particular needs.

I make it a point to try to NEVER recommend one type of battery over another. Sorry not much help with this one, I can give you some pointers but you need to post more info on your intended use and how you plan to store the CT when not in use.

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AnswerID: 247726   Submitted: Monday, Jun 18, 2007 at 19:18

fujimiester replied:

My auto sparky was going to put in battery cable right through to the anderson plug at the back of the 4by
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Reply 6 of 7
AnswerID: 247827   Submitted: Tuesday, Jun 19, 2007 at 08:43

Ray Bates replied:

Just My two penny worth. My auxillery battery is mounted on the draw bar of my caravan. I assume that your third battery is in the towed vehicle.
I use 18mm3 (4g) cable through a 175amp Anderson plug.
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