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Old 06-16-2011, 05:08 AM   #1
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Default setting up e.s.c. and battery long wire run!

is it better to have the e.s.c. as close to the motor as possible, with a long wire run to the battery, or the battery short and the e.s.c. long wire run??
i ask because i am setting up a plane that has a .35 pusher on the tail of the plane, right in front of that i installed the e.s.c. with a wire run of less than 6 inches from motor to e.s.c., then the wire from the e.s.c. must go forward, down the fuse, to the battery, which is 24 inches away. is this the right way

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Old 06-16-2011, 05:21 AM   #2
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Originally Posted by iflyrc1012 View Post
is it better to have the e.s.c. as close to the motor as possible, with a long wire run to the battery, or the battery short and the e.s.c. long wire run??
i ask because i am setting up a plane that has a .35 pusher on the tail of the plane, right in front of that i installed the e.s.c. with a wire run of less than 6 inches from motor to e.s.c., then the wire from the e.s.c. must go forward, down the fuse, to the battery, which is 24 inches away. is this the right way
From what I've read, don't change the length of the Red/Black wires between the battery and the ESC. If you need to extend things, add to the three wires between the ESC and the motor.

That makes sense, since you are adding in series, the inductance of the wires to the orders of magnitude greater inductance of the motor windings.

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Old 06-16-2011, 06:07 AM   #3
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o.k. i'm screwed. the motor and e.s.c must go in the rear of the plane, and the battery must go all the way forward in order to balance the airplane.if i set it up this way,
will it work? or am i just gonna fry the whole set-up?

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Old 06-16-2011, 07:51 AM   #4
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Your setup is not ideal but it may work ok anyway.

In general, its far better to keep the battery wires as short as possible. Like Denny said, long battery wires make for higher inductance. What that means is that your esc sees higher voltage ripple (voltage spikes) on the battery side. The esc has capacitors on that side to help smooth those spikes out. The higher the ripple, the harder - and hotter - those caps have to work.

If they cant handle the spikes, the controller dies.

If you cant change the long wires, or its too much trouble - like in your case - there are a few things you can do to improve your odds of success.

1)Use hi quality, higher C rated packs that can EASILY handle the load. Its the voltage drop at the battery on every motor pulse that is the basic source of those spikes. Better quality packs and higher C rated packs have a lower Ir and so less voltage drop and therefore lower spikes. This is the single best thing you can do. Crappy packs or just marginal packs are the single biggest cause for hi voltage ripple.

1A)use good connectors and over sized wire. Remember - you want the resistance between the battery and esc as low as possible. Dont scrimp here or you good packs are a waste

2)Use a quality controller thats well over sized. In other words - if you expect to pull 30 amps peak, use a good quality 60 amp controller. if you using Hobby City stuff, go with an 80 amp controller.

3)Add some additional hi quality Low ESR caps to the controller as close to the controller as possible. Its best to have them be the same size and voltage and ESR value as the ones on there now.

4)Braid the battery wires - although Im not sure how effective that one really is and it adds a good bit to the weight - you need extra wire for the braid.

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Old 06-16-2011, 11:57 AM   #5
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Originally Posted by Larry3215 View Post
... 1)Use hi quality, higher C rated packs that can EASILY handle the load. Its the voltage drop at the battery on every motor pulse that is the basic source of those spikes. ...
The killing voltage spikes are higher than battery voltage and are caused by wire inductance, not by battery or wire resistance. Using thicker wire is a good idea though, it gives lower voltage drop under load and inductance is reduced slightly as a bonus.

Originally Posted by Larry3215 View Post
... Braid the battery wires - although Im not sure how effective that one really is and it adds a good bit to the weight ...
No need to braid, would give extra resistance too. Just keep the red+ wires and the black- wire as close together as possible to reduce inductance as much as possible.

ALLcontroller manufacturers say the same, too long battery wires will kill controller over time. But there are solutions/workarounds if you cannot but extend the battery wires. See
http://www.rcgroups.com/forums/showthread.php?t=952523

Contents
  • Problem
  • Solution
  • Rules of thumb
  • Capacitor type and polarity
  • How to add extra capacitors
  • Expert/manufacturer opinions
  • DIY pictures

Excellent thread by someone who apparently is into controller and/or power supply design. Explanation, considerations, capacitor choice, capacitor sources, albeit with a slight e-bike slant:
http://endless-sphere.com/forums/vie...p?f=30&t=22194
Capacitor source e.g.:
http://fightercatracing.com/index.ph...chk=1&Itemid=1

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Old 06-16-2011, 06:45 PM   #6
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Ron, I got that information from the guys at Castle. They are always harping on using good packs with low Ir as one of the best ways to reduce ripple.

Its my understanding that if there was no voltage drop, there would be nothing for the inductance of the wires to act on and there would be no ripple. You need some resistance to cause a drop in voltage under load for the inductance to amplify.

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Old 06-16-2011, 08:34 PM   #7
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The guys at castle do have a point Larry. Thank you

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Old 06-16-2011, 09:52 PM   #8
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I forgot to thank you for posting the links and the tip on (not)braiding

As always Ron, you are a continuous source of excellent information!

I think I need a signature.
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Old 06-16-2011, 10:27 PM   #9
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Originally Posted by ron_van_sommeren View Post
The killing voltage spikes are higher than battery voltage and are caused by wire inductance, not by battery or wire resistance.
I did testing on this subject a year or three ago. The voltage spikes on a piece of #13 wire about 2 feet long, when a 5 ampere resisive load was switched on and off was nearly double that of the battery voltage.

So if you've got a 21 volt 6S2P A123 battery pack, that voltage spike will be some 40 volts DC. It's only a microsecond or two long, but that microsecond of spike voltage is what does the ESC's in.

Those big electrolytic capacitors in the inputs of the ESC's are what knocks that 40 volt spike down to acceptable values. There is a lot of current behind those spikes, so you don't want to work those aluminum electrolytic capacitors to hard.

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Old 06-16-2011, 11:46 PM   #10
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thanks for the help guys. i'll go with a larger than needed e.s.c.(70 amp), larger wire, shrink wrapped to together, and top of the line connectors. Any suggestions on what connectors to use? the length of the wire from the e.s.c. to the battery is gonna be about 18 inches to 24 inches. it will not be a high output high voltage airplane, i'm figuring it will pull about 45 amps.

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Old 06-17-2011, 12:44 AM   #11
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That's a lot of extra battery wire. Add extra caps.

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Old 06-17-2011, 05:38 AM   #12
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Originally Posted by iflyrc1012 View Post
thanks for the help guys. i'll go with a larger than needed e.s.c.(70 amp), larger wire, shrink wrapped to together, and top of the line connectors. Any suggestions on what connectors to use? the length of the wire from the e.s.c. to the battery is gonna be about 18 inches to 24 inches. it will not be a high output high voltage airplane, i'm figuring it will pull about 45 amps.
Can't go wrong with the Anderson Powerpoles, and associated crimper.

Just put the wire into the terminal, crimp it with the $39 tool, insert pin into the plastic shell, done. Zero soldering, I'm using it on a system pulling 70 Amps without issues.

http://www.powerwerx.com/anderson-po...pole-sets.html

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Old 06-17-2011, 05:38 AM   #13
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Originally Posted by ron_van_sommeren View Post
That's a lot of extra battery wire. Add extra caps.
Agreed:
You can't add the extra wire between the ESC and the motor???

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Old 06-17-2011, 02:46 PM   #14
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Originally Posted by kyleservicetech View Post
Agreed:
You can't add the extra wire between the ESC and the motor???
+2 Extend the motor wires. It will help you to have the ESC near the battery for CG anyway. Run three motor wires then can run 24" with zero issues. Battery wires at 45amps that long is asking for trouble.

Motor side. Trust us.
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Old 06-18-2011, 02:01 AM   #15
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the esc MUST GO 5 INCHES in front of the motor...that is where the scale air inlet and outlet are. there is no other way to install it AND keep it cool. others have flown this airframe set up this way without incident, so that's how it's going in. i just wanted a few more experienced opinions on how to do it this way, it never hurts to ask for others to chime in. Thanks again for the advice guys.

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Old 06-18-2011, 02:07 AM   #16
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Originally Posted by iflyrc1012 View Post
the esc MUST GO 5 INCHES in front of the motor...that is where the scale air inlet and outlet are. there is no other way to install it AND keep it cool. others have flown this airframe set up this way without incident, so that's how it's going in. i just wanted a few more experienced opinions on how to do it this way, it never hurts to ask for others to chime in. Thanks again for the advice guys.
You wanted voices of experience, we all agree, then you ignore that? Cracks me up.

To each his own.

Best of luck with 24" battery leads.

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Old 06-18-2011, 02:51 AM   #17
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it needs to have longer motor leads. this f-16 has the motor in the back. esc is close to mid section. i just made leads with bullet connectors so i can remove if needed.
the hatch for the battery/esc is the dark area behind the canopy


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Old 06-18-2011, 03:33 AM   #18
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Mike,
what cracks you up??? i tried to put you on my ignore list but it seems MODERATORS
CAN'T BE PUT ON THE IGNORE LIST!! do me a favor? keep your little snipes to yourself.
picking fights in cyber space is the sign of ,,,,,,

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Old 06-18-2011, 03:35 AM   #19
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Originally Posted by iflyrc1012 View Post
Mike,
what cracks you up??? i tried to put you on my ignore list but it seems MODERATORS
CAN'T BE PUT ON THE IGNORE LIST!! do me a favor? keep your little snipes to yourself.
picking fights in cyber space is the sign of a sick little mans mind.
A simple question - why ask advice if you have your plan all mapped out. Why?
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Old 06-18-2011, 03:41 AM   #20
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i simply asked if it were POSSIBLE TO DO IT THAT WAY? i realize it may not be the best way, but it is possible, and in order not to ruin the scale appearance of the model by cutting a vent in the fuse where none exists on the scale subject, i will take some of the advise offered here such as using heavy wire, and keeping them together, also using other connectors than i had wanted to use. but moving the e.s.c. is not an option.

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Old 06-18-2011, 03:49 AM   #21
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Originally Posted by iflyrc1012 View Post
but moving the e.s.c. is not an option.
Just a note here. Those ESC current ratings are determined by checking heat rise during operation with a given amount of airflow past the unit. If the ESC is installed with zero air flow, their is no way for the ESC to get rid of the heat it generates. It doesn't take a lot of airflow, only a few MPH will do it.

If the ESC does overheat, you've got two issues. One, the ESC overheats, and shuts down. Or worse.

Second, if you are using the built in BEC (Battery Elimination Circuit) of the ESC, it could shut down. That shuts down battery power to your receiver. The BEC will have to get really hot to do this. But with several servos, and no way for the ESC and it's BEC to get rid of the heat, you could have a problem.

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Old 06-18-2011, 03:52 AM   #22
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you can install one of those 12.00 mini fans that the put on r/c cars.

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Old 06-18-2011, 03:53 AM   #23
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Originally Posted by iflyrc1012 View Post
is it better to have the e.s.c. as close to the motor as possible, with a long wire run to the battery, or the battery short and the e.s.c. long wire run??
i ask because i am setting up a plane that has a .35 pusher on the tail of the plane, right in front of that i installed the e.s.c. with a wire run of less than 6 inches from motor to e.s.c., then the wire from the e.s.c. must go forward, down the fuse, to the battery, which is 24 inches away. is this the right way
When I read this I see a person asking - "is this the right way". Not "I have to do it this way is that going to cause trouble".

Again you certainly don't have to follow anyone's advice. It is your equipment. Sometimes setups are not ideal.

I just found it odd you asked but did not seem interested in what we thought best. Some of us have learned this lesson from the school of hard knocks.

By the way - the battery needs cooling how you doing that?

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Old 06-18-2011, 03:54 PM   #24
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Originally Posted by iflyrc1012 View Post
... i will take some of the advise offered here such as using heavy wire, and keeping them together ...
All good, but not enough, add capacitors, as ALL esc manufacturers say.

About better controller cooling:
www.mgm-compro.com
-> tech.info
-> controller cooling in models

Prettig weekend Ron

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Old 06-18-2011, 10:32 PM   #25
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Dont stop asking for help, there are many good people here. I have found there is no shortage of advise, but theres a real shortage of good advice. When the majority of the people say the same thing, there is most likely some truth to it. Then again some will get mad if you dont do just as they say, ignore them. Anyone with sincere advice will offer it, and wish you the best without being defensive or upset if you dont do as they say. If they are directive in nature, ignore, follow your instincts.
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