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Power Wire Length?

Power Wire Length?

Old 12-29-2003, 09:11 AM
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Default okay, okay

since I'm about to wire my xxx-s I would have to use a long wire going to either the (+) or (-), so which would be better will just use 14gauge wire.
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Old 12-29-2003, 09:33 AM
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I did a little research and this is what I found:

"Current is the flow of electrical charges (usually electrons) in an electrical circuit. When you hook a lightbulb to a flashlight battery, the current flows from the negative terminal to the positive terminal, always in the same direction. This is called DIRECT CURRENT(DC).
Electrical current from a standard household outlet changes direction 60 times each second (50 times per second in Europe). Because the current flows first in one direction and then the other, this is called ALTERNATING CURRENT(AC)."

Our RC CARS use DC. Thats why I think we should have our best battery in the negative to sustain the pack and lessen premature dumping. Because if it is the other way, if the worst battery is in the negative and it dumps, no matter how much is left on the other cells, you race is over, but if the best battery is in the negative, it will keep sending "electrons" over the cells that is low or have dump. And hopefully prevent DNF....ouch!!!! This is my suggestion to folks like me who got just a few packs to race with, unlike Factory Guys who have almost perfect "matched" pack.

With regards to the lenght of wire. I keep it as short as possible on both ends to avoid among other things, creating interference with your receiver. Keep your solder contact point clean and to a minimum. But if your running stock, I will not really matter a lot. But then if your in modifieds, it will up to some extent......just my 2 cents on this issue.
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Old 12-29-2003, 10:06 AM
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Originally posted by davepull
blah blah blah look at your car I have a tC3 with the battery positive in the back I run 1 red wire + from the speedo to the motor to the battery. now if power in these speedo's flowed positive to neg the your motor would run flat out all the time. look at the car and think about it
no it wouldnt run all the time.
because its separated [the circuit ] by the speedo.
some people think they just know everything.so why dont you read what i put above.
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Old 12-29-2003, 10:07 AM
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Originally posted by Airwide
No offense, but please don't post information if you don't know what you're talking about.
i agree.
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Old 12-29-2003, 11:02 AM
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It doesn't matter which wire is shorter. The current flows though all wires equaly for all intents and purposes. (it doesn't even matter which way the electrons ar flowing). I say for all intents a purposes, because some of the current goes to the Receiver and ESC control circuitry, and that current does not flow to the Motor, but this current is basicly not siginficant for this discussion, even if you dont use a receiver pack.

This last part I am not 100% on, perhaps only 99% sure... If your running a 3 wire ESC as most of us probably are, there should be very little current flowing to the ESC from/to the positive side of the battery/motor, only the BEC current would have to go though the Positive wire to the ESC, so in that segment the lenght of wire really doesn't matter.

In a 4 wire setup... all wire length is important... the shorter the better, all wire segments mater equaly.

I do however disagree that anyone who says you will never be able to notice the differances between 1 and 12 inches of wire... I my opion if your driving is good, you should deffintely see lower lap times if you shorten your wires by 12"....
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Old 12-29-2003, 11:05 AM
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Just make both wires even and put an end to this class on electricity( i did learn something i think)
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Old 12-29-2003, 01:53 PM
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Default It doesnt matter which way the current flows !

At least not in touring cars with normal ESC's.

The point is, that the WIRE from the battery positive pole, goes directly to the motor. So the length of the ESC positive wire, doesnt matter, since no power is transferred. It's only used by the ESC, to sense the voltage.

So the wires that matters, when it's about low resistance, are the wire from the batt plus pole to the motor, from the batt negative pole to the ESC and the negative from the ESC to motor negative.

These wires should be as thick and short as possible. Prefreable with a lot of cores inside, since the current moves on the surface of the metal inside, thus a bigger surface is better.
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Old 12-29-2003, 04:25 PM
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Both wires as short as possible ,all negatives short ,positive to motor short ,motor to speedo not really important
the longer the wire the greater the resistance
the greater the resistance the more the voltage drop

electricity flows negative to positive and believe it or not lightning goes up not down
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Old 12-29-2003, 09:14 PM
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So, on the subject of mysteries(nobody really seems to know here!), if a tree falls and nobody is around to hear it, does it make a sound?? To my knowledge(and as told to me by my uncle, who is an automotive electrician), ELECTRON flow is positive to negative, but that is neither here nor there. With that logic, then a heavier spring on the negative brush and a softer one on the positive would be the hot setup. Take your motor, put a light spring on the positive side and a heavy one on the negative side and see what happens. It will suck. No power.
Now, maybe there is a NEGLIGIBLE gain from shortening the negative wire as much as possible, since its current passes through the speedo, and the positive doesn't. This is assuming the speedo provides significant resistance, but most ESC's today provide negligible resistance.
So, I'd say that this topic is null, and the only good advice is to keep your wires as short as you can.

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Old 12-29-2003, 09:40 PM
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where is Charlie from Novak he know the true answer to this question.
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Old 12-30-2003, 12:36 PM
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I'm not Charlie, but I'd like to toss in my 2 degreed EE cents.

The positive line going to the ESC is used to power the ESC, as well as some internal sensing so it can be the best little ESC it can be. The motor speed is controlled on the negative side. In engineering, this is known as a low side switch, but you probably don't care about that.

Conventional current flows form + to -. If you get down and dirty, electron charge flow is from - to +. Dont' ask why, that's just the way it is. No one really cares about true charge flow except some very esoteric scientests. Stick to conventional current flow. It'll keep you from getting a headache.

The length of the wires only matters in the sense that shorter is generally better.
That said, the resistance of an extra few inches of 12 or 14AWG wire is less important than making sure you have good solder joints everywhere. A bad joint can have a resistance 10 to 100x as much as an inch of wire.

The worst case power loss in 6" of 14AWG wire is insignificant, compared to the losses in lap time due to being a few inches off the perfect line or being a tooth off the optimum gearing for your driving style or tagging a board on a hairpin.

If you really believe losing a few inches of wire will make you faster, you'd better be the best driver who ever lived, or you're just fooling yourself.

Wire it so your car is neat and clean and easy to work on. If that means an extra inch or two of wire, so be it. Use good connectors, they have less resistance than an inch of 14AWG wire, and make life easier on you and your batteries. Make nice shiny solder joints.

Don't obsess over a few inches of wire. It doesn't matter. I promise.

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Old 12-30-2003, 02:12 PM
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I guess this is the only time that "shorter is better". LOL LOL LOL I agree that clean driving will have more effect that the length of the wire. One brush against the boards will negate all the gain in millivolts that you hope to get. Thanks for your input, dpaton.
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Old 12-30-2003, 03:06 PM
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46, I'm not speaking in terms of being faster, I'm speaking in terms of effeciency for the speedo so it isn't being strained in a wrongful way. Kinda like a stereo amplifier in a car, you want your negative power wire to the amp as short as possible since the amp has to use the cars chassis as part of its power source. If that negative wire to the chassis is long I'm sure the amp won't be as effecient as it could be visa versa with an R/C ESC.
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Old 12-30-2003, 04:22 PM
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OK I read this whole thread so Ill put my opinion in here too. It doesnt matter wich wire is shorter just that Both wires in the circuit are as short as possible. You want the entire circuit to be as short as you can. It would do no good to have a short negative wire if the positive has to be longer to compensate. You have to use the resistance of the entire circuit it doesnt matter where it is in the loop. Here is a wise example Budda once told me. If you have a 60 foot pipe and a valve that has to be installed that will only flow 1gpm it doesnt matter if it were at the start or the end of the pipe (the valve representing the total resistance of the ciurcuit) It will still flow only 1gpm.

So Um.... No I dont think it matters, shorten up witchever one doesnt match the color of your car.
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Old 12-30-2003, 06:30 PM
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Originally posted by proudwinner
I'm speaking in terms of effeciency for the speedo so it isn't being strained in a wrongful way. Kinda like a stereo amplifier in a car, you want your negative power wire to the amp as short as possible since the amp has to use the cars chassis as part of its power source. If that negative wire to the chassis is long I'm sure the amp won't be as effecient as it could be visa versa with an R/C ESC.
Sorry PW, but you're wrong.

<EE hat on>

It really doesn't matter where the extra few thousandths of an ohm is placed in the circuit. I promise.

In a car, it's a totally different story because of the nature of a car frame as a (very poor) conductor. The kind of ground conductor has no effect whatsoever on the efficiency of a car amplifier. If the ground sucks, the amp won't get full voltage, and will run at less than full power. Efficiency is governed by some very different factors (power supply topology and amplifier biasing mainly, which are both totally independent of voltage)

What we're talking about is nice fat wires, carrying a few amps at a few volts (if this was several thousand of either, things would be different. At less than 10V...well...). If one is a few inches longer than the other, the ESC really couldn't care less. The ESC only worries about total voltage should be applied to the motor, and what pulse width to apply to the drive FETs to make sure the motor gets that voltage. It can't see the wire from itself to the battery, it only sees (indirectly, via the applied voltage and current) the resistance from the total length of cable in the mot-ESC-batt loop, which is so small as to be impossible to measure accurately with a regular meter, once you exclude the winding resistance of the motor (which swamps everything else hundreds of times over).

<EE hat off>

I'll say it again, the ESC doesn't care. Leave negative longer. Leave positive longer. It doesn't matter.

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