Wire Size, AWG and Funny Numbers

It amazes me how the smallest details can escape you.  Or, well, escape me.  Wire gauge seems simple enough, it’s a number that gets smaller as the wire gets bigger, right?  14 gauge wire is smaller than 12 gauge, and like that.  I’m running 4 gauge welding wire on my batteries and motor, and others are running 2 gauge.

So, the first thing is that if you’re a wire nerd, you refer to it as 4 AWG.  AWG refers to the American Wire Gauge standard, (also known as the Browne and Sharpe wire gauge) and it’s been in common use since the 1800s.

So, what threw me is that you see, for example 4 AWG, right?  Then you see numbers like 4/0 AWG.  You may guess that 4/0 AWG is just another way to say 4 AWG, you’d be wrong.  It goes like this.  4 AWG, 3 AWG, 2 AWG, 1 AWG, 0 AWG, 00 AWG, 000 AWG, 0000 AWG.  Another way to name this is with numbers, referring to the zeros.  That is, 0000 can also be called 4/0, (or, like, 4 zeros, or in wire-nerd-speak, “four-aught”).  Where a 4AWG wire is a little less than a 1/4″ thick, a 4/0 is about a half-inch thick.  Big difference.

Here’s a link to one of these clever little gages: General Tools 20 American Standard Wire Round Gage, and here’s a ton of wire-nerd info on the Wikipedia, and here’s a cool table of info for standard wire gauges that we use for EVs:

AWG	Diameter						Copper resistance		NEC copper wire ampacity with 60/75/90 °C insulation (A)		Fusing Current (copper)
	in.	mm					(Ω/km) (mΩ/m)	(Ω/kFT) (mΩ/ft)			Preece (~10s)	Onder-donk (1s)	Onder-donk (32ms)
0000 (4/0)	.460	11.684					0.1608	0.04901	195 / 230 / 260			31 kA	173 kA
000 (3/0)	.409	10.404					0.2028	0.06180	165 / 200 / 225			24.5 kA	137 kA
00 (2/0)	.364	9.266					0.2557	0.07793	145 / 175 / 195			19.5 kA	109 kA
0 (1/0)	.324	8.252					0.3224	0.09827	125 / 150 / 170		1.9 kA	15.5 kA	87 kA
1	.289	7.348					0.4066	0.1239	110 / 130 / 150		1.6 kA	12 kA	68 kA
2	.257	6.544					0.5127	0.1563	95 / 115 / 130		1.3 kA	9.7 kA	54 kA
3	.229	5.827					0.6465	0.1970	85 / 100 / 110		1.1 kA	7.7 kA	43 kA
4	.204	5.189					0.8152	0.2485	70 / 85 / 95		946 A	6.1 kA	34 kA

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Here’s a nice little list of some essential tools, with my suggestions.

 

A good multi meter is essential.  This is my choice.

FLUKE 15B+ F15B+ Auto Range Digital Probe Multimeter

 

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Digital calipers are nice – non conductive plastic ones are a smart move.

Starrett 799A-6/150 Digital Caliper

Wiha 41101 Digital Caliper

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For crimping large lugs –

Forney 57637 Lug Crimping Tool

 

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If brute force doesn’t work, you’re not using enough:

Central Hydraulics 12 Ton Shop Press 

 

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Making connections…

Soldering Iron kit

 

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…and sealing them up.

Heat Gun

 

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Portable hacksaw power

Sawzall

 

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’nuff said.

BFH (Big —- Hammer)

 

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Wire sizes and funny numbers…

Wire Gauge