cobrajocky

I've seen a few discussions on this topic, the maximum length that the wire between a brushless motor and ESC can be. I'm looking for a concrete answer, based on REAL electronics engineering fundamentals, not old wives tales (don't tell my wife I said that).

Some model planes, especially Glow to Electric conversions just don't allow for putting the ESC within a standard wire length (as delivered with the motors and ESC), so can distances like 9", 12" 15", 20" be acceptable? Can changing the wire guage size conpensate for longer distances?

Would love answers from the Forums Electronics Engineers, state your MS of EE origin or IEEE Certificate :^) Seriously.

DaveFlynn

I don't have a degree, however from working with motors for a long time I can tell you that the wires can be looong if they are thick. Ugly's book (little yellow book), electrical contractor supply and wholesalers have them, is a good source of tables and charts.

jdetray

Even though I (briefly) majored in EE in college, my credentials do not meet your stringent criteria. I ended up as a computer magazine editor!

The usual recommendation is that if you must lengthen wires, it's better to lengthen the ESC-to-motor wires rather than the ESC-to-battery wires. This is what several ESC manufacturers and vendors recommend.

Here is an thread where the technical reasons are debated:
[link=http://www.rcgroups.com/forums/showthread.php?t=952523]Careful! - long battery wires will kill ESC[/link]

There are plenty of links in the thread, so you can spend an hour or so reading everything and then draw your own conclusions.

- Jeff

cobrajocky

Small world, I wrote for Byte mag back in the late 70''s till nearly the sad end of the print copy and a few other mags, then I got a legit job in Marketing Communications (exec level) at HP. So how many free Mac and iPuds has Apple given you to bribe a disturbingly glowing review? Rumor is Walty Goatberg has a garage full of Macs, iPuds and a briefcase full of iPhonies. (I HATE Macs and Apple)

Anyway, I've read the same about lengthening only between the motor and ESC, and never between the ESC and Battery. But I've not read anywhere what amount of lengthening is acceptable. Wait, that sounds like a lot of emails I get. No that's something else.

No sweat on a brief major in EE, learning to use a slide rule killed my interest in a Mechanical Engineering degree ... oh god am I dating myself. Basket weaving was so much more ..... pleasant.

jdetray

A small world indeed!

I worked for a different computer magazine publisher located in the same small town as Byte (Peterborough, NH). There were about 25 technical magazines published in and around that tiny community in the 70s, 80s, and 90s. It was a fantastic atmosphere in which to work.

I remember well when one of the first Macs appeared in our offices. It seemed like a toy. Well, I suppose it WAS a toy at that point. A computer without a command line? Ridiculous! And we all laughed at those silly little 3.5-inch floppies. Today, my wife and I use PCs 99% of the time, though I also have a Mac Mini on my desk. It's a nice little unit (6x6x2 inches), but it only gets turned on about once a month.

- Jeff

cobrajocky

Ahhhh, the good old days ... CP/M, Kaypro, Osborne, Tandy TRS-80, oh my Altair 8800. Wayne Green was the Editor/Pub when I started, then Virginia took order one day (when she dumped Wayne I believe). I was not in NH (too freakin cold); but writing for them from my location in the "Silicon Cereal Bowl", Frisco - the land of Flakes, Nuts and Fruits (cereal bowl, old joke). I belonged to the Homebrew Computer club out at Stanford, after getting out of the Air Force and Nam, so I was in the middle of everything going on in the fast lane. I used to write stories later on a TRS-80 model 100 portable and I still have it. The first REAL "laptop" computer, fit in my briefcase.

Mac have always been and always will be toys. I used to love Apple computers, had an Apple I and then sold it because it was too limited ('77 I think). Had a couple others like the TRS-80 desk top, then bought a new Apple ][e - FIRST mass produced "American" computer to be OUT SOURCED (Canada and then Taiwan). Ya, Apple the great "American Computer Company", also the first to out source. I loved that ][e Pro and still have it too. Even have the "mouse option" and the CP/M card.

Now Macs are Chinese Sweatshop junk. Always buy Apple Care, because like "toys", they rarely last beyond the standard warranty without problems. I've had 4 Macs in recent years that all died in one form or another between 1 month to 8 months after the warranty lapsed. That is the big secret that the paid off Apple Hacks in the media never write about. One G3 iBook I had, had to been repaired by Apple FIVE TIMES (three Logic Boards and two LCD's) in two and one half years. Thank god I bought Apple Care on that one.

This why I love RC. When, and it will break .... it's because I crashed it!

cyclops2

Long motor leads are the SAFEST. Large or undersized leads. KEEP the motor leads loosely twisted & as far away from the servo & antenna leads in a plane body. SPOT glue them in place securly!!!!!!!!! At a crash scene, you will not know that the vibrated loose leads wound up right next to the servo & antenna leads.........KAABOOM.

motor leads very bottom of plane. all others at the very top of the plane.

or on opposite sides of the plane.

tIANci

When is it deemed as too long?, basically do not extend it? May 6"-8" be reasonable?

Walt Thyng

My Feedback: (9)

for info on motor lead length, do a search for Bob Boucher (Google or RCU, RCG). There was a discussion of this recently on one or the other of those sites. As the "Father of electric flight" (Roland might argue with that), I think he's about as expert an expert as you can get.

Essence of the article was that esc to motor wires can be as long as you want providing they are of appropriate gauge to overcome resistance.
Walt

cyclops2

I have no problems testing ESC's with a amp meter that has 48" long leads. That means the + side of the battery has a 100" long lead in it & the - side has a 24" long lead in it.
All new equipment is ALWAYS checked out with this setup to be sure it works OK at WOT.

NO problems yet. 30 years of brushed & brushless.............I NEVER run anything over the maximum VOLTS or AMPS !!!!!!!! Maybe that is really why nothing blows up.

I have run 2 sets 48" motor leads on a 80" A-10 with no problems. NO exceeding the Maxes.

Rich

cobrajocky

You're completely wrong if you are saying "basically do not extend it? May 6"-8" be reasonable?" . Most of the evidence I'm seeing here and from other forum sites indicate 12+ inches in wire length between the BL motor and ESC is not any problem.

I'm looking at needing a 12" wire length for a project I'm doing with a 3meter EP Glider; but now I'm curious what the max length can be and how to compensate by perhaps changing wire gauge.

tIANci

Sorry I meant the wire between ESC and batt as some have stated that a long wire can spoil the ESC. Sometimes no matter what you cannot have the ESC wires that long as you may not have sufficient cooling. Example is my MidWest CAP 232. The ESC is on the motor mounting box BUT since I load my batts under the box the ESC to batt wires are short but some new planes have the batts in the tank compartment and it balances well, the ESC wire will need to be extended if you wish to maintain the same place on the motor box for cooling.

For a 40cc plane the motor box itself is already about 6"-8" long. Hence, my query ... not to forget when we use a parallel or series connector there will be about an extra 6" being put between the ESC and batt. What do we do then?

Red Scholefield

My Feedback: (9)

From Model Aviation - Battery Clinic column July 08:

LONG BATTERY TO ESC WIRES OR LONG MOTOR WIRES FROM ESC?

There has been a fair amount of controversy on this subject as e-flighters move into multi-engine models. Logic would tell us that just lengthening the battery leads so the ESCs could be located in the engine nacelles for cooling would be the way to go. Well that isn’t the way it goes according to those that design the ESCs.

Patrick del Castillo of Castle Controllers has this to say, “On the HV controllers especially, the battery-ESC length is the critical length. You should not extend the wires more than a total length of greater than 12" without additional capacitors. On the motor side, length is less critical 18" is fine.

While Bob Boucher (Astrobob) http://www.astroflight.com has this to say on the subject with a bit more detail,
“I will repeat the message previously given. I hope you heed some sound advice
based on theory and practice.
1. Wire resistance my rob you of a bit of power but will not destroy
your speed control or motor.
2. Wire inductance will not damage your motor nor will you be able to
detect any effect even with 100 feet of wire.
3. Wire inductance will kill the mosfets in your control and may even blow the caps.

You must keep battery wires as short as practical. Short means 1 foot or less.
Brushed or brushless, it makes no difference.

Here are some example of problems some customer have had;
1. Blimp with 30 feet of wire to ESC near the steering motor in the tail.
ESC rating 60 volts 50amps, motor load at 12v was 20 amps. Result instant smoke first run of motor. I replaced control at no cost. Same result instant smoke. Then I was told about long wires and ran a test with 3 ft cord result 30 volt switching spikes on 100 uf input capacitor. I had the customer put the ESC near battery in gondola. 30 ft wire to motor-end of problems.

We have customers running very long wires to motors for industrial applications
with no problems, hundreds of feet or more.

With ESC keep battery wires short. PERIOD!

But if you must run long battery leads Shultze shows us how to add extra capacitors (English and German): http://www.schulze-elektronik-gmbh.d...e/gfutc-de.pdf

tIANci

Okay ... the God's of ESC have spoken, keep her less than 12". This is good info, very very good ...

cobrajocky

Red,

Thank you so very much for researching these quotes from notable experts in the field. The info stated is gold and invaluable. In fact, I'm going to cut-n-paste it to a word doc and pass it around at the two flying club fields I attend and to my buds at the couple city parks we "park flyers" congregate at weekend mornings.

Salute to the great RC Universe moderators! Just like the calvary.

Best regards

jdetray

This thread ought to be a Sticky, because this question comes up often.

- Jeff

ron_van_sommeren

This is not a wire resistance issue, it's a problem caused by the inductance of the battery wires.

Manufacturer's statements (they all say the same, including Bob Boucher), rules of thumb, workarounds, tricks, explanations:
http://www.rcgroups.com/forums/showthread.php?t=952523

If you fly WOT most, all of the time, it's not that much of an issue, not much switching going on then. Also, some manufacturers have plenty of built-in capacitor-reserve and -quality, others haven't.


I worked for the [link=http://www.fnl.nl/]Dutch pendant[/link] of the German [link=http://www.heise.de/ct/]C't computer magazine[/link]. Booooooring, translating German to Dutch, not technical enough for me. Christian Persson, the C't editor, wrote the e-flight "Drive Calculator": www.yahoogroups.com/group/d-calc .

Vriendelijke groeten Ron

jesse1919

Well, I'm not one to brag but if you insist... I have a MSEE specializing in power electronics and motor drives. I've been working in the aerospace drives industry for 5 years. I'm not exactly a guru but I have worked with several.

That said... I have have nothing to add. LOL Well almost everything's been said but I'll try to clean it up.

1) Inductance from battery to ESC can destroy the ESC especially when you run the ESC at max rated cells (volts). 12 inches max is a good rule of thumb BUT reducing the loop area between the + and - wires is just as important. Twist or tie the wires (loosely) together.

2) Any length from ESC to motor in an RC plane will basically work BUT: [ul][*] you should still loosely twist/ tie the wires together to reduce radio interference. The three wires act like antennas and placing the three together helps to cancel the fields. Keep them away from antenas and servo wires. [*] you always lose efficiency from resistive (heating) losses in any wire - shorter is better. If you have to go longer, you should use thicker wire. (How big depends and too many things to make a general recommendation)[*] thick long wires are heavy!
[/ul]

Jesse

mtryon

hopefully this isn't too far off topic...

In lengthening the motor / esc leads, where can say, 18 awg aluminum wire, be purchased?
I can't find it anywhere.

Something tells me I shouldn't try to solder aluminum to copper... seeing as how all the wiring in electric planes have aluminum...

jdetray

I have never seen any aluminum wiring in electric planes. Wiring is nearly always copper, and that's what you should use.

- Jeff