Author Topic: Wiring size standard  (Read 843 times)

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Offline Gonzo_Descente

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Wiring size standard
« on: January 20, 2018, 11:29:06 PM »
I have here the Gilfillan Standard for wire sizes, which I used for decades designing test fixtures for military and commercial electronics.  In some cases it might be a little overkill, but it will work.

Offline utherjorge

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Re: Wiring size standard
« Reply #1 on: January 21, 2018, 04:39:02 AM »
Gonzo, do you have one that includes all the way down to 0 and beyond?

I ask because I've seen the same kinda thing, but if I wanted to run a line from my alt or battery off an isolator to the rear, to charge a battery box, the recommendation is basically to go down to 0 to avoid much loss of power over that distance.

Offline Gonzo_Descente

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Re: Wiring size standard
« Reply #2 on: January 21, 2018, 07:30:10 AM »
No, the standard only goes to #6, which should hold a continuous 30 amps without overheating or loss of voltage. I will go look for specs of bigger wire and get back to you.

Offline utherjorge

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Re: Wiring size standard
« Reply #3 on: January 21, 2018, 07:57:19 AM »
My understanding was it wasn't just the gauge of wire, but also how far away from its source you wanted to go without a drop in voltage.

Without going crazy descriptive, a future plan is a solar array tacked into a second battery. However, I don't think I would need a second battery all the time. So, I would run a longer cable off the isolator I'll put in and shenanigans behind one of the cards by the rear seat. Battery box (or some such) behind the rear seat. I would use a heavy-gauge cable from the battery under the hood rearward, likely with anderson connectors, to avoid a voltage drop.

Offline Marine Airedale

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Re: Wiring size standard
« Reply #4 on: January 21, 2018, 11:13:53 AM »
If going inside of the passenger compartment be certain it is a sealed battery.  We want to keep you alive, we have not extracted all the data out of you yet  :039:
Lester, my friends call me 'Les'
Location: Central Oregon Coast, USA
Vehicle: 1992 Rocky SE

"Everything is better wrapped in bacon" "Are these for everyone" My lovely wife and best friend, many years before we were married.

Offline Gonzo_Descente

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Re: Wiring size standard
« Reply #5 on: January 21, 2018, 01:46:18 PM »
All right, here is another chart which can be useful.  Start by deciding how much current you will need, and how long the wire needs to be.

Using the chart data, and the formula E=IR, where E=Voltage, I=current, and R=resistance you can calculate the voltage drop for any wire of choice.

For example a 10 foot long piece of #6 wire would have a resistance of 0.0444 ohms and if it were carrying 30 amps of current, it would develop 1.332 Volts.

There will be some other small voltage losses in the connectors/lugs etc, but for a 12 Volt system, the loss will leave you about 10.668 Volts or less.

Now if you were to use a 10 foot piece of number 0 wire, the loss would be about .02946 Volt, leaving you with about 11.97 Volts or less.

PLEASE NOTE that the electrical resistance in the first chart is for 1000 feet but for only 100 feet in the second chart!
« Last Edit: January 21, 2018, 01:50:57 PM by Gonzo_Descente »

Offline utherjorge

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Re: Wiring size standard
« Reply #6 on: January 21, 2018, 01:57:42 PM »
Thank you! That looks like what I've seen before.