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I feel like I have gone down a rabbit hole and came out knowing nothing. I understand this is a really basic question. My son and I are building a simple RC. It is using 4 1.5v (AAA) batteries in series. So if what I have gathered is correct that is 6v. What I cannot seem to figure out is what size wire should I get. I honestly thought this would be in the spec of the wire. Maybe I am not seeing it. I need a pretty good length and want to make sure before I go off and buy this.

I know there has to be a formula for this but what I am googling is not turning it up.

nerdlyist
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  • It is not because it is affected by how hot the ambient temperature is, the cooling air flow of the wire, and surrounding wires (other heat sources) and the insulation material's max temp. The formula is a nasty super physics differential equation. Just use a table made for not too abnormal environmental conditions. Or just use 22AWG wire because AAA batteries are too weak to put out a lot of current anyways. How long a length? Wire heating up because wire is too small and losing voltage over a long length because it is too small are two different things. – DKNguyen Jan 22 '20 at 01:54
  • Wire size is dictated by current and allowable temperature rise. There are *lots* of questions about this already. https://electronics.stackexchange.com/q/122351/2028 https://electronics.stackexchange.com/q/389832/2028 https://electronics.stackexchange.com/q/386782/2028 – JYelton Jan 22 '20 at 02:00
  • @DKNguyen Around 5-7 ft. The car is connected via the wire so needs some room to move. – nerdlyist Jan 22 '20 at 02:32
  • @JYelton I am sure it does if I was not just getting started on this adventure. I rember why I went computer science over electrical engineer now. – nerdlyist Jan 22 '20 at 02:35
  • @nerdlyist You might want to go 20AWG. Current won't be enough to heat the wire but you may lose too much voltage due to length and your voltage is low enough to begin with. At shorter lengths, Heating is per wire length and does not change as wire gets longer or shorter (obviously) but voltage loss increases as it gets longer and becomes the limiting factor. You could also just use more series batteries to compensate for voltage loss. Sounds like the batteries will be in the controller not the car. – DKNguyen Jan 22 '20 at 02:40
  • The ability to search online for previous questions is just as valuable in computer science as in electrical engineering. I'm not trying to be impolite, but duplicate questions are duplicate questions. – JYelton Jan 22 '20 at 03:17
  • For currents under say 1A and lengths under 1 metre "anything available" is usually fine **EXCEPT** NEVER use wire so fine or fragile such that it occasionally breaks "just because it wants to" with normal handling. I have seen commercial products with wire like that. Don't do it. – Russell McMahon Jan 22 '20 at 04:09
  • @jyelton I admit yes I could have done more review. But this did get me an answer (a pretty good one and simple) and hopefully it will help some other people out there. Sometimes duplicates lead to different answers. – nerdlyist Jan 22 '20 at 04:54
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    I'll toss out another weird bit of trivia. Each gauge change (say, going from #20 to #21) is 1 dB. So 6 gauges means 4 times or one-quarter, up or down. #10 is \$1\:\frac{\text{m}\Omega}{\text{ft}}\$. So #16 is \$4\:\frac{\text{m}\Omega}{\text{ft}}\$. It's pretty easy to remember and work around things from this simple rule of thumb and one memorized benchmark. – jonk Jan 22 '20 at 07:55

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normally I solid grab some scrap wire and see how it goes.

For AAA current will probably be less than 1A so AWG29 or fatter should be fine

https://www.powerstream.com/Wire_Size.htm

I'm looking at the chassis wiring column.

I would use AWG24 salvaged from an old ethernet patch cable (because I gave lots of that here)

Jasen Слава Україні
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  • Well you at the least saved me money. I have spools of Ethernet cord to try out! That chart is helpful at least in pointing in what I need to understand a little better. – nerdlyist Jan 22 '20 at 02:36