Hmm. I was considering using the 4 gauge monster cable I had laying around. I might rethink that now. I asked my electronics teacher last year about the 4g vs 2g. He wouldn't give me a straight forward yes or no. He basically told me to figure it out. He makes me think. *****. So I haven't tried anything yet, but my plan is to measure the amp draw of the motor and the resistance of the length of wire I plan to use. Apply Ohms law. I x R = V . Amp draw times resistance equals the expected voltage drop across the wire I plan to use.

For what its worth French Monster cable is no better than any other copper 4 gauge. I too thought because there were more strands it was better for some reason, nope just more flexible. This is from my prof. mouth.

 

Man I was way off. It got to me while in the shower. lol Ohms law doesn't work here.

So I looked it up. Heres a copy and paste.

A very rough way to calculate a possible current draw if you know the motor's operating voltage is to use the fact that 1 hp is approximately equal to 0.75 kiloWatts. So 3 hp = 3 x 0.75 = 2.25 kW.

Now, knowing that the actual efficiency of a motor depends entirely upon its design type, we shall have to assume an efficiency factor for the conversion of electrical power to mechanical power.

If we assume the motor is only 50% efficient then, to produce 3 hp, it will have to be supplied with electrical power of at least 2 x 2.25 = 4.5 kW.

Since Power P (Watts) = V (Volts) x I (Current in Amps), the current drawn I would therefore be given by I= P/V:

At 12 Volts DC: 4,500 / 12 = 375 Amps. (This would be a typical peak starting current drawn by, say, the starter motor of a small carengine in Summer. In Winter it might get to 500 Amps or more!)

 

I tried 2 - 4 gauge wires and had no luck. These things need a lot of power. 0 gauge is probably over kill but I had a 100ft roll of it.

 

Well I used to do this for a living and all those calculations threw me for a loop, so I just go from experience. As for all those strands not making the wire carry more amps, and just be more flexible; I have to disagree. When looking at distributors amp rating charts the finer strand cables are not only more flexible, but the density of the wire is much higher for the equal size, so the amp rating can be double what some lesser strand wires is.
#2 thhn will carry a rated 95 amps, while #2 machine tool cable carries 200 amps.
A std. #2 thhn will cary half the amperage of a machine tool or welding cable #2. If you take a look at circular mils there's far less resistance in a cable that's got hundreds of strands vs. one that's got 12-16 larger strands. I always use the fine strand cable for long battery runs. On short runs it really doesn't matter much.

 

Single 0 gauge wire is not overkill if it's regular strand, and if it's fine strand it's only slightly over what I run. I use #1 fine strand cable, so you're only one size larger if it's fine strand.

 

There is a noticeable difference. I had a $300 roll of cable laying around from my old sterios. I use to be big in to the car audio scene.

Try running a few fosgate 10001 on plain old 0 gauge. Simply wont happen. But they run great on high end 0 gauge. I dont know the math, but I can promise that there is a difference.
The amps will cut out with a cheap 0 gauge.

I also race slot cars, and the group 20 motors show a speed increase simply by running a finer strand cable. Do to weight you want the smallest wire possible. So small strand it a must.

 

LOL That math was my life last semester. Exactly that math. It got out of control towards the end with trig. I will say that before asking about the wire my theory was that, electricity runs around the wire not through it. If you give the current a bigger path (more strands) there should be less resistance. I wanna try and defend my teacher here, but not to the point of destroying my credibility. I guess he may have been blowing me off. It was at the beginning one of first class I ever had with the guy. He is god like to me but again I only have two professors for electronics, not much to compare him to. His son works for Tesla (electric car), if that means anything.

 

I was an apprentice back when the earth began, well maybe not quite, but in 1974. So I have to really strain to remember some of that stuff, especially since I retired and tried to forget it!
One thing I do remember from apprenticeship school was conductors are like water. The best conductor possible is a single bare conductor because it's solid and no gaps between strands. Wrap it in insulation, and like a insulated pipe it retains heat, so heat will reduce it's ability to flow amps. Put 6 strands to flow amps, and the spaces between the strands will be voids that wont flow amps. Lessen those spaces and you get more strands within the same diameter and less space equals more amps. Use really fine strands that have no space between the strands and it's still not as good as the soild single conductor, but we're getting much closer.
I wont argue theory with any instructor as they'll always win the battle of wits with me, but I know what works in the real world.

 

Oh yeah, there still beating the it flows like water drum. I took basic electronics and electronics math last semester. They're co-requisites and 15 weeks of pure hell. Now I'm struggling with digital circuitry and Boolean Algebra. This stuff makes Ohms law look like ABC's.

 

You have my sympathy Damon! I know you're working and going to school, and that's what we all did back then. Electrical apprenticeship was 5 years of school 4 nights a week, and work 5 days a week or more. I knew more than one guy who got divorced before he took his journeyman's license exam. Hard classes, but even harder when you work and have a wife and family!