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Old Dec 17, 2009, 07:47 PM
Garry
Tumble weed country Eastern Washington
Joined Aug 2004
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Question
extending wires to motor

I need to extend the wires from ESC to motor about 6 to 7 inches, these wires will be encased in epoxy. I was going to put connectors on both ends of these wires to connect esc and motor . Can I use regular automotive type wire as it is never going to move.
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Old Dec 17, 2009, 09:22 PM
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Mayday!Mayday!'s Avatar
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It's better to extend wires on the battery side than the motor.

Look at the similar threads below.
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Old Dec 17, 2009, 09:34 PM
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I believe it is okay to extend the wires to the motor from the ESC. 6-7 inches isn't that long anyway. Its a bigger problem with inductance when extending wires from the battery to the ESC, especially when running the ESC near its limits.

As for choosing the wire, use something with an appropriate guage for the current used. I would choose something 100% copper if available. Automotive wire likely has a thicker strand, not a problem if you aren't moving it around as you say.
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Old Dec 17, 2009, 09:47 PM
Garry
Tumble weed country Eastern Washington
Joined Aug 2004
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Thanks alot, I thought it would be ok to use auto wire but thought I would ask to be sure. Yes it is copper wire 16 gauge from motor to esc about 30amps max.
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Old Dec 18, 2009, 02:22 AM
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Quote:
Originally Posted by Mayday!Mayday! View Post
It's better to extend wires on the battery side than the motor.

Look at the similar threads below.
I think you've got it the wrong way round . All the threads I've read say that you can extend the motor wires, but you shouldn't extend the battery wires significantly unless you take special precautions.

I can't view the "threads below" now that I'm typing, but do a search for a long one by Ron van Sommeren for a full explanation of the problem and the solutions

Edit: Here you are http://www.rcgroups.com/forums/showt...t=battery+lead
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Old Dec 18, 2009, 04:19 AM
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Staffs, UK
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Quote:
Originally Posted by Mayday!Mayday! View Post
It's better to extend wires on the battery side than the motor.

Look at the similar threads below.
If you'd taken your own advice and looked at the similar threads below you'd know that it's much better to extend motor to ESC wires. Extending the wires between battery and ESC can be downright dangerous (for brushless motor/ESC only...brushed motors don't care ).

BTW if the wires are really going to be fully embedded in epoxy you want to increase the diameter of them a bit. Epoxy is a pretty good heat insulator so they'll get hotter than you might expect in there and 16ga for 30A is not exactly huge.

Steve
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Old Dec 18, 2009, 04:42 AM
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Quote:
Originally Posted by slipstick View Post
(for brushless motor/ESC only...brushed motors don't care ).
Brushed cares too:

Per astrobob (http://www.rcgroups.com/forums/showp...2&postcount=32)

"3. wire inductance will kill the mosfets in your control and may even blow the caps
I am a design engineer and manufacturer of motors and controls for over 30 years.
you must keep battery wires as short as practical . short means 1 foot or less.
brushed or brushless makes no difference."
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Old Dec 18, 2009, 08:20 AM
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Mayday!Mayday!'s Avatar
Columbus,Ohio
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There is alot of info about not extending battery wires, or only to a certain length but not much is said that it is ok to extend motor wires. So-

discussed this before with Castle Creations for their ESCs:

- For extending the battery side wires, they essentially stated that the wires could be extended to a maximum of 12"; beyond that they recommend adding a capacitor at the ESC terminals equal in size to the capacitor already installed on the ESC for every 6" of wire added beyond 12".

- For extending the motor wires, they were not very specific on recommendtions (noting that it depends on specific/individual ESC components), but added that they have 'typically' seen motor side leads extended up to a maximum 24" total length.
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Old Dec 18, 2009, 11:11 AM
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Quote:
Originally Posted by MGeo View Post
Brushed cares too:

Per astrobob (http://www.rcgroups.com/forums/showp...2&postcount=32)

"3. wire inductance will kill the mosfets in your control and may even blow the caps
I am a design engineer and manufacturer of motors and controls for over 30 years.
you must keep battery wires as short as practical . short means 1 foot or less.
brushed or brushless makes no difference."
Well I still learn something new from time to time...often, as in this case, too late to be of any practical use .

I think the largest brushed motor I still use is a 7mm pager motor and it's pretty unlikely I'm going to need wires much longer than 1ft on any plane using that .

Steve
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Old Dec 18, 2009, 04:49 PM
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The whole issue is a tempest in a teapot. In most cases even extending beyond 12" will cause little trouble. Each of the RCG gurus have their own pet peave and for Ron it seems to be those low ESR caps. Others lock their brakes over things like never parallel regs, charge lipos in the house, etc..

IMO the real danger for these caps is heat. Unless you are involved with extremely high voltage and high current setups there is no concern with adding a few inches to battery wires. The finger test is a good indcator if these are dissipating too much ripple.

Personally I tend to extend motor wires but not for some imagined FET killing spike reasons but simply because it's easier and cheaper to redo 3 wires instead of 5.
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Old Dec 19, 2009, 10:10 AM
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I'm with MayDay on this one. Seems to me I have that correspondence he speaks of in which a rep from Castle Creations addressed this very issue. What I got out of the answer was that it's perfectly OK to go ahead and extend the motor wires first, and then if need be, extend the battery wires. I'll have to find that document, but I'm almost positive he was speaking about adding on lengths of a foot to each set of wires if need be.

I have seen ESC's mounted in ridiculous places on planes because the owners were scared to death to add on wiring.

Chuck
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Old Dec 19, 2009, 10:44 AM
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Well if it matters,

Almost all the guys who build Steve's parkjet (big ones) extended the battery wires with no issues.
One of the ones that caught my attention was Lucien. I would think dealing with motors and esc's all day he would know.

I have a few jets with wires extended on the battery side, been that way for years and no problem.
When Ron posted he thoughts on this, there was a few threads started and debated back and forth about it.
I find it easier to extend the battery side for ease of access and CG issues.
This is only my thoughts/experience, I am no expert. However if Castle tells me it's ok, then I will take their word on it.
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Old Dec 19, 2009, 12:53 PM
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Yep, it's entirely possible that you'll get away with extending either motor or battery wires. But what we were reacting to was you claiming it was actually preferable to extend the battery side.

Castle, Shulze, Jeti and Kontronics are all fairly well known manufacturers of ESCs and they all state that it is better to extend the motor wires (by almost any length). They also state that precautions are necessary when extending the battery side more than a few inches.

If you want to convince anyone, against all the advice from the people who should know, that "It's better to extend wires on the battery side than the motor" (not just that they'll probably get away with it fairly often) then you could do with a bit more evidence .

Steve
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Old Dec 20, 2009, 07:18 AM
Aka: Tom Jenkins
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Palm Beach County, Fl.
Joined Aug 2008
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I wound up adding 12ga to an ARC motor. I cut the motor wires behind the preinstalled 3mm connectors, used a dremel wire wheel to clean off the enamel and direct soldered the fine stranded 12ga ends side by side to the motor wires and heat shrinked like a wire nut, gathered the ends, shrank all three ends together sorta cone style with the tails pointing to the shaft end, heat shrink them for airflow and slipped a plastic cone on from an E-flight fan kit, HiTemp RTV'd it to the end cap of the motor. Cured it 24hrs and the cap is stuck very well. I don't think there will be any proton loss with this fine strand 12ga wire. Pretty slick app on a het/arc combo huh?
Edit: drilled and tapped 2mm holes on back of motor can, didn't trust the rtv.
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Old Jan 07, 2010, 06:33 PM
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USA, NC, Hendersonville
Joined Jul 2005
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So let's talk about how SHORT the wires between motor and esc can be. I'm using an equivalent to the Mega 16/15/3 and a Castle 35 ( not pushing to hard ).

For CG on a PUSHER WING the farther aft I can get the controller the better, any thoughts ....... thanks..
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