Wolvee

EDIT: I don't want to give out bad info.

ibd2328

iTrader: (2)

False.

ibd2328

iTrader: (2)

Current typically runs on the outside of the wire and the more strands you have, the more infintestimally small gaps you have.

jprevat

iTrader: (1)

When it comes to electricity i will not question your know how ibd. Oh yeh Im doing the upgrade this afternoon so lets hope it goes nice and easy. lol

Wolvee

And here I thought I knew it all, lol. I got it backwards. It's been a long time since I worked w/ Mr. Ohm and even longer since the MECP cert.

Call it a Senior moment.

ibd2328

iTrader: (2)

Haha no prob man. I use to teach physics so I try to stay up to date on that stuff.

Justin61391

Quote:
Originally Posted by Sxynerd
If you can find "thinner" strand cable that's the same gauge and copper % that would be more ideal. Someone mentioned thicker strands were better but the thinker the strands, the more resistance it will see.

Honestly, I don't know that it really matters in this application a whole lot but all other things being equal thinner strands have less resistance. (Cost vs. benefit)

I wouldn't think that was false. Like you said, current runs on the surface area of the conductor typically in DC. Like you said, the more strands, the higher the number of gaps you have.

However, the wire with thinner strands will also have a higher strand count, as it has the same volume of space to take up to meet its true AWG size.
This would mean that the thinner strands have a higher number of gaps, but it does NOT mean it has more resistance.
For one, the gaps will decrease in size dramatically as strand count is raised. (Like you said, infinitesimally small)
Secondly, the surface area of all of the strands will then be increased significantly as well.

Think about putting big rocks in a bucket then shaking the bucket for a long time (don't even have to shake it actually), compared to putting smaller rocks in the bucket. Which of the sums of these two choices has more total surface area? The small rocks do.
One may also think about taking a volume of space (say the volume of a 0 gauge one strand wire) and putting more and more strands in, decreasing the strand size but increasing the count, as you go. Look at the gaps, what happens to it? It decreases, and surface area increases.


Unless I'm missing something here, I would think the less amount of strands would have more resistance, making a higher strand count desirable not only for resistance, but also for flexibility and vibration reasons.

I am not trying to offend anyone, just would like an actual reason behind it. I'm always up for learning, so please correct me if I am wrong, or add something I am missing if that is the case.

Going to the extreme, take a solid wire measuring in at 2 AWG (or any size) and then take a wire with a 2000 strand count, and see which one has more conductor surface area. It will be the one with the higher strand count.

ibd2328

iTrader: (2)

If a conductor nearly relied on surface area alone, the longer the wire the more conductive it would be?? That's just not logical. Do you think a 12ga wire span over 100miles is going to have more conductivity than a 12ga wire at 1 ft?

Check out a physics book with some calc based electromagnetic problems. Or look at some high voltage heavy equipment machines.

Justin61391

Of course a longer wire is going to have more resistance, that is true in any case. Resistance will always go up as the path the current takes is lengthened. The conductor should have more surface area PER length of the conductor. Resistance is never zero, with that being said, you want the path to be as short as possible. On top of it being as short as possible, you also want it to have more surface area on which the current may travel.

One cannot attemp to change only one side of the equation (the higher strand wire length and not the lower strand wire length). You cannot compare the resistance of a lower strand wire (lets say 50 strands) to a higher strand wire (lets say 5145 strands) if you change the length of the higher strand to induce more resistance. Apples and oranges.
In order to compare properly, you must change only one variable(strand count in this case), not two.
If both were increased to 100 miles, the one with more strands would have MUCH less resistance in it.

High voltage does not equate to high current. High voltage situations generally are used to reduce current draw. I believe we are dealing with low voltage (16V or less), high current draws, are we not? Alot of situations in which high voltage is used, calls for a long length of wire, and high voltage is used to reduce the voltage drop across wire, otherwise the high amperage draw would waste energy due to resistance given off as heat dissipation. (Power company high-voltage transmission lines for example. Even then, many are made from aluminum braided lines surrounding another conductor, using copper every time is just not cost-efficient for them, and it is much heavier and harder to work with.)

I have taken calculus based physics courses and a few electrical engineering courses when I was still in school. I don't really see where you are coming from, but am intrigued.
Please give me an example of a situation in which less strands in the same gauge wire means less resistance and I will look into it.

Justin61391

Regardless, the write-up was done pretty well, and I'm sure it helped many people. Nicely done. We'd like to see how you cleaned up the dual-battery install.

I'm planning to do a dual battery setup (back-to-back so I can keep resorvoir in stock location-hopefully) around the new year if all goes well.
I don't like only having one battery. I want one strictly dedicated to starting, and the other for accessories, while still allowing the accessory one to be used by a relay for starting if needed.
My plan is to do that, along with upgrading the body to ground cable, and at least a 180 ampere alternator. I also need to take out my current wire going to my amp and replace with 1/0 and then use a distribution block and go to 4 and 8 AWG to my goodies. I've got power inverter, 4 fogs, amplifier, a few small things such as more cigarette lighters, etc. on the center console, brake-light bar, etc. and I just don't trust having one battery.
Anyways, I'm still not sure how I want to go about wiring it in, isolation etc... I don't want to put too much of a strain on the alternator, so I'm still a little indecisive. I was thinking maybe have the starter one being the primary one to charge, and making the accessory one secondary (that is only charging one at a time, and only charging the accessory battery after the primary starting battery has enough charge.)I'm still not swayed either way completely though. I will have to take a look at that other thread you made to get some ideas about how I want to go about doing that. Decisions, decisions...