12V system Wire Sizing

12V system Wire Sizing

Postby Monkeyz on Wed Nov 06, 2013 5:25 pm

I am in the process of designing my Aux Battery system and Trip panel for accessories and I couldn't find a simple chart to help size the wiring, so after a chat to the electrical dept at work we came up with this. I would advise double checking the sizing with a professional before doing any wiring....I hope this is of some use it is set for 12V Car electrics to help determine gauge of wire for a given amp draw over a given distance to minimize current loss. Imperial and metric tables for the old farts and young bucks.

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Re: 12V system Wire Sizing

Postby 4wd26 on Wed Nov 06, 2013 5:32 pm

very cool- thanks
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Re: 12V system Wire Sizing

Postby Quinny on Wed Nov 06, 2013 5:47 pm

That's very interesting ... Thanks for that Monkey ;)
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Re: 12V system Wire Sizing

Postby Kingbrown on Thu Nov 07, 2013 4:48 pm

It'd be so much simpler for everyone if they'd refer to mm2 - like the rest of the electrical industry :evil:
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Re: 12V system Wire Sizing

Postby NowForThe5th on Thu Nov 07, 2013 4:56 pm

True, but those tables are from US sites where they haven't quite realised that the rest of the world has gone metric. Then they'll refuse to change because it wasn't their idea and some clever cookie will develop their own "metric system" with 10 inches to the metre. :roll:
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Re: 12V system Wire Sizing

Postby viking shippy on Thu Nov 07, 2013 6:26 pm

Quinny wrote:That's very interesting ... Thanks for that Monkey ;)


Go on Quinny I dare you
to calculate by how many times you over engineered your wiring job..lol he he ha ha
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Re: 12V system Wire Sizing

Postby RHKTriton on Fri Nov 08, 2013 3:03 pm

Yanks!

They'll just want to mod the "free rape (er little Johnny's trade) agreement" so that they can flog more imperial cable to us.

Never hurts to go over-size for most 12V apps.

We have to realise that the manufacturers go absolute minimum on everything.

Best one I came across a couple of years ago was discussing wiring with a local panel repair centre.

They were stumped that replacement wire looms for Hyundais were always too short.

On investigation they found out the the Factory orders the wiring shorter than required to save money.
Before installation on the production line, the looms are put on stretching machines to bring them up to required fitting lengths.

Why bother "engineering" anything? Cars don't set on fire! ......
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Re: 12V system Wire Sizing

Postby tondo12 on Wed Feb 19, 2014 3:45 pm

Anyone know where I can buy a 12V wiring harness with relay from. All i can find on Ebay is the button 12V wiring kits, i dont want a button 1
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Re: 12V system Wire Sizing

Postby motoz on Wed Feb 19, 2014 3:49 pm

tondo12 wrote:Anyone know where I can buy a 12V wiring harness with relay from. All i can find on Ebay is the button 12V wiring kits, i dont want a button 1


What do you want the harness for?
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Re: 12V system Wire Sizing

Postby tondo12 on Wed Feb 19, 2014 3:57 pm

Im wiring these
http://www.ebay.com.au/itm/10-30v-15-WA ... 4861500cee

Sorry I should have made that clear in the original post.

I wanting to wire them in each side of the number, mainly for camping purposes.
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Re: 12V system Wire Sizing

Postby motoz on Wed Feb 19, 2014 4:00 pm

I've just run a fused feed via a switch for all my LED lights. Never bothered with a relay.
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Re: 12V system Wire Sizing

Postby snakesoup on Wed Feb 19, 2014 4:01 pm

shouldn't need a relay for them mate jst use a 20amp switch inline and fused of coarse ..
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Re: 12V system Wire Sizing

Postby tondo12 on Wed Feb 19, 2014 4:06 pm

Would it hurt using a Relay. Ive seen alot of diagrams around with a Realy, and will probably wire up some more lights down the track. :?:
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Re: 12V system Wire Sizing

Postby koshari on Wed Feb 19, 2014 4:10 pm

Kingbrown wrote:It'd be so much simpler for everyone if they'd refer to mm2 - like the rest of the electrical industry :evil:


this x100

so many times i hear of people sourcing 6mm auto cable that is about 1.8mm^2 CSA.

when you buy cable you pay for the copper.
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Re: 12V system Wire Sizing

Postby tondo12 on Wed Apr 02, 2014 3:49 pm

This has probably been posted before,
How many Amps does the MN 2013 alternator put out,
Im looking at buying this, http://www.ebay.com.au/itm/321089674007
What is the max i could use before it does damage?
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Re: 12V system Wire Sizing

Postby Monkeyz on Wed Apr 02, 2014 5:09 pm

tondo12 wrote:This has probably been posted before,
How many Amps does the MN 2013 alternator put out,
Im looking at buying this, http://www.ebay.com.au/itm/321089674007
What is the max i could use before it does damage?



Nice but have you considered this ...

http://www.ebay.com.au/itm/PROJECTA-DBC150K-150-AMP-CAR-ELECTRONIC-DUAL-BATTERY-ISOLATOR-CHARGER-SYSTEM-KIT-/290776322717?pt=AU_Car_Parts_Accessories&hash=item43b39e929d&_uhb=1

and as far as im aware (happy to be corrected) this will not cause any issues with the alternator etc...

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Re: 12V system Wire Sizing

Postby Cowboy Dave on Wed Apr 02, 2014 5:15 pm

Personal opinion, but I reckon redarc quality shits all over projecta stuff. I've never bought a projecta item that didn't break which is why I won't buy their stuff again. Your results may vary however.
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Re: 12V system Wire Sizing

Postby Monkeyz on Wed Apr 02, 2014 5:22 pm

okay what about

http://www.ebay.com.au/itm/like/121125553096?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=107

Ctek appears to have a good name....I just prefer an electronic system

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Re: 12V system Wire Sizing

Postby Cowboy Dave on Wed Apr 02, 2014 5:27 pm

That is the unit I am running in mine :D
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Re: 12V system Wire Sizing

Postby tondo12 on Wed Apr 02, 2014 6:00 pm

So we would have no issues with 150amp running off the alterntor?
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Re: 12V system Wire Sizing

Postby JamoGLXR on Wed Apr 02, 2014 6:14 pm

you might need a different voltage depending on what battery you choose.
something is ringing in my mind that Constant Voltage is better for charging because if the volts are too low it will float at best.

AGMs need 14.4v
Gels a bit less but take longer
Lead acid is lower again

i even thought of making my own DC-DC charger. Constant current for the first 85% then finish on Constant Voltage to keep the batteries happy.


im happy to be proved wrong because im looking into this myself.
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Re: 12V system Wire Sizing

Postby Cowboy Dave on Wed Apr 02, 2014 6:38 pm

I'm no sparky, but I can't see that thing ever pulling 150 amps. A winch will pull more than that but a battery isolator/charger?
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Re: 12V system Wire Sizing

Postby JamoGLXR on Wed Apr 02, 2014 6:53 pm

Cowboy Dave wrote:I'm no sparky, but I can't see that thing ever pulling 150 amps. A winch will pull more than that but a battery isolator/charger?


Correct. a winch is up to 400Amps. i imagine a dual battery system would pull 30A at best..

maybe the 100A or 150A ratings are just an idea of how much the internals can handle giving you a yard stick that is used to compare against other models. like the useless measure of lumens. its light intensity not a usable unit like lux
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Re: 12V system Wire Sizing

Postby viking shippy on Wed Apr 02, 2014 7:25 pm

Jamoglxr the Ctech dual dc to dc charger looks after the charging of the second battery regardless of type..up to 14.5 volts....it regulates solar imput and once the second battery is charged tops up your starting battery...top bit of gear..
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Re: 12V system Wire Sizing

Postby viking shippy on Wed Apr 02, 2014 7:35 pm

Tondo 12...Your alternator will only put out just below it's rated output ie 90 amps...When its regulator senses the battery is below a specified voltage..it supply's a charge voltage at a regulated amperage..ie 12.5 and cuts of at 13.5. Whilst doing that it supply's enough power to the battery to charge whilst all the time adjusting for the demand for your cars electrical system..
The battery is where the big amps get pulled from your system....ie a winch under strain 400amps.....that's why the cables to a winch is so big...compared to the alternators cable that is 1/2 the size...
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