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Old Mar 05, 2012, 01:21 PM
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I went down that road too, but all advise is that it's only a matter of time before the caps in the ESCs blow.
There's much discussion on it, including here, but one advise I would give is that silicone isn't moisture proof and has the ability to allow moisture through it. I build solar panels and its for this reason they won't use silicone. They use the equivalent of laminating sheets, which is in fact the same as hot glue, so that may be a better bet, and some do use it without any reported problems.....so far!

Luke
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Old Mar 05, 2012, 08:41 PM
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Darwin Australia
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Quote:
Originally Posted by Luke2000 View Post
It's always a discussion matter, but after a lot of trawling, the consensus seems to have short battery to ESC wires, and ESC to motor length is not a problem. I have my ESCs in the fuselage and they are fine. Braid the cables from the ESC to the motors if you are running them with or near the servo cables.

If you do put the ESC in the nacelle (waterproofing???), the consensus is to use extra caps in the ESCs, same ratings.

Luke
One of the members of my club built scale model of twin jet called the IAI Westwind. This aeroplane looks similar to a Learjet with two rear mounted jet motors. The member had to mount the battery well forward in the nose to balance the model and he mounted the ESCs in the tail near the EDF fans. So he had a long battery leads and short ESC leads. He was always blowing up ESCs even though he was using Castle Creations ESCs that were rated well in excess of the fans current draw..

Westwind link
http://en.wikipedia.org/wiki/IAI_Westwind

Ken
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Old Mar 06, 2012, 09:30 AM
Bob S.
France, Auvergne, Luneau
Joined Aug 2008
81 Posts
Which ESC?

I am using 2 Turnigy L2205-1350 Brushless Motors, coupled with 2 20A Brushless ESC's, and even, this seems to get hot. What's wrong in me goiung for a 40A ESC? Won't this solve the heat question? Sorry for all the (stupid) questions, but I'm new to all this.
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Old Mar 06, 2012, 12:15 PM
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Renton, WA, US
Joined Oct 2007
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Quote:
Originally Posted by Bo43 View Post
I am using 2 Turnigy L2205-1350 Brushless Motors, coupled with 2 20A Brushless ESC's, and even, this seems to get hot. What's wrong in me goiung for a 40A ESC? Won't this solve the heat question? Sorry for all the (stupid) questions, but I'm new to all this.
There is no reason you cannot run 40 amp ESC's. They will work just fine, but they are heavier and a little more expensive. I'm always trying to cut both weight and cost, so for me 20 amps ESC's have worked out just fine.

ESC's will warm up when they run close to their limits. That is normal, but if they are really hot then you could have something else going on. On a different plane, I had one get really hot even without the motor running, and I eventually figured out that I had a short circuiting servo.

BTW, If you don't already have one, a power meter is a great investment!
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Old Mar 06, 2012, 12:24 PM
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Good advise fly time. I read in some thread that if you can't keep your finger on the ESC beyond 5 seconds, it's running too hot. I bought a infra red thermometer from HK, can't remember but it was cheap. I thought that the ESCs may be overheating in the fuselage 'cos they felt hot, but the thermo showed they were well within the tolerance, can' remember the figures tho.
HKs site shows a max of 13.5A for those motors and recommends an 18A ESC, so 20A is fine. Check the servos all right.

Luke
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Old Mar 06, 2012, 01:46 PM
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upstate ny
Joined Jun 2003
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with any set up you need at least 25% more esc than the amps
the system is drawing : eg : with a 20 amp esc the max would be
15 amps.

So Bo43 using 40 amp speed contol's won't hurt . I do it all the time
cost is only a couple of bucks and weight almost nothing .

a very useful tool for any electric model is this, its a battery fuel gauge
in real time: so never run the battery out , it tell's the amp' s and temps
real time , so if you want to know how hot your esc is during a flight
put the sensor on esc and see temp real time as you fly
worth the money - earlier versions of this weren't as good ,but the new
one is great

http://www.hobbyking.com/hobbyking/s...FmAh%5FV2.html

http://www.hobbyking.com/hobbyking/s...Fadd%5Fon.html

http://www.hobbyking.com/hobbyking/s...ntenna%5F.html
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Old Mar 06, 2012, 02:43 PM
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Darwin Australia
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Using an ESC that has a greatly larger Amp capacity than the motor is actually drawing can cause problems in the case of a stalled propeller. ESCs have an over Amperage / over tempreature safety cut off. If the Amp capacity of the ESC is too high it is possible to burn out a motor before the cut out activates.

Ken
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Old Mar 06, 2012, 03:21 PM
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Renton, WA, US
Joined Oct 2007
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My 2 cents on the ESC debate: I have been flying electric for almost 5 years and have accumulated nearly 20 planes in my hangar. Most of the ESC's that I use in my planes have less than a 25% margin between motor rating and ESC rating (5-10%, if that), and I have never (knock on wood) had a brushless ESC go bad on me.

More important than the motor rating is how much power you are are actually drawing with a particular battery and prop. Only a power meter will tell you that, and it's a good idea to measure it for a couple of different reasons. First is the one we have been discussing, which is the capacity of the ESC. Secondly is the motor itself. Most motors run most efficiently at under 80% of their max amp rating. If you have a motor capable of 13 amps, and you run it at 13 amps, you should consider propping down. In many cases you will get better performance out of that same motor if you are running it at 10 or 11 amps.

Another thing to consider, and maybe this is why I don't worry too much about my ESC's running at close to their limits, is that a bench test where the motor is running hard but the plane is standing still will almost always (EDF's and high-pitch props sometimes being the exception) pull considerably more power than it will when the plane is moving forward through the air. As the plane moves forward, the prop will unload and draw fewer amps. So if I bench test at max amps for an ESC, I know that I will only get the same amp draw when I'm hanging it on the prop at WOT. Even 3D planes are rarely hanging on the prop at full throttle.
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Old Mar 06, 2012, 07:30 PM
6 months to finish a rtf
pulsery2k1's Avatar
upstate ny
Joined Jun 2003
1,832 Posts
fly time

better to be safe than sorry, but you must also relize that if you
change a prop you can also change how much power (amps)
the motor will use .
a motor drawing 15 amps with a 8x4 prop may
draw 18 amps with a 8x6 ,or 22 amps with an 8x8 prop
so the static wot amp reading may not hold true in flight :
EG: some one at our club flew his new 1400 mm P-40
static test it was drawing 32-34 amps it comes down
esc super hot ,battery swollen ????
we fly it again with my Quanum 2.4Ghz Telemetry System
and see the amps up near 55 . so not all props unload in flight
he replaced the stock prop with a master Airsrew with less pitch
and it fine
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Old Mar 07, 2012, 02:35 AM
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Canada, ON, Toronto
Joined Jun 2010
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Too long battery wires will kill your ESC over time:

http://www.rcgroups.com/forums/showt...highlight=kill

This has been my experience with boats, where even an inch more blew caps on some of my ESCs.
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Old Mar 07, 2012, 07:13 AM
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Montreal
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Quote:
Originally Posted by GP73 View Post
Too long battery wires will kill your ESC over time:
http://www.rcgroups.com/forums/showt...highlight=kill
This has been my experience with boats, where even an inch more blew caps on some of my ESCs.
thanks for the link GP73... interesting...

my personnal opinion & experience :

--all of my plane use long battery power leads and short 3 phase wire to motor
(batt. wire usualy 20 to 50 cm and motor 3 phase approx. 5cm)
never had a single failure

--i think that the distance need to be find : what is too long ? 50cm is not so long for me...

--most of ESC failure are du to overheating or bad size match in my opinion
& also poor user that want to find a 5$ ESC = wrong we need a minimal quality = turnigy plush...
Even Castle creation may reduce part quality to put much more money in there pocket LOL
6s ESC mean 27V would require at least 50+ volts capacitors to be safe

--i fly my CL415 with ESC inside the nacell because i want to reduce the overhall
RF noise on the airframe (i fly it FPV !)

--if you are afraid of long batt. wire failure, either twist the +&- lead or run them
far away from each other in 2 different channel OR add extra capacitor to ESC input
(50+V)

--i always use smaller AWG gauge as necessary for batt. lead to save weight
& reduce possible short current burst avalaible to ESC... EX: 25amp esc on my
CL415 would need more than 12awg : i chose 16awg because average esc current needs
are less than 10 amp

--i work with ROCKWELL ESC for living and we frequently send the main DC bus
far away to dissipate over voltage (dynamique bracking resistance bank) .

When we run too long 3 phase motor leads , we have to add choke coil
to reduce peak voltage that dammage motor (effect of long 3 phase motor lead)

i have good reason to prevent failure when i send my airplanes over
atlantic ocean !
COREL Mercalli addon test (3 min 12 sec)
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Old Mar 07, 2012, 07:45 AM
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Canada, ON, Toronto
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Quote:
Originally Posted by ggtronic View Post
thanks for the link GP73... interesting...

my personnal opinion & experience :
Maybe you should post it on that thread as well, to discuss it with the other guys there.
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Old Mar 07, 2012, 08:06 AM
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ggtronic's Avatar
Montreal
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Quote:
Originally Posted by GP73 View Post
Maybe you should post it on that thread as well, to discuss it with the other guys there.
good idea... in need to read it all
first

yet... they stated that 30cm batt. lead are OK

i still suggest to use ESC feed minimal wire gauge size (reduce avalaible burst current) and use only 3s lipo with 4s lipo rated ESC
or find 5 or 6s ESC to become more reliable...

The initial capacitor charge (when you plug your battery and see a spike !) is what's trying to kill ESC
cap in my opinion, specially with 4s lipo use (max ESC tolerance). see these under rated cap voltage :
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Old Mar 08, 2012, 11:14 AM
Bob S.
France, Auvergne, Luneau
Joined Aug 2008
81 Posts
Wire extensions for Motor

aaa
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Last edited by Bo43; Mar 08, 2012 at 11:19 AM. Reason: Mistake
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Old Mar 08, 2012, 11:18 AM
Bob S.
France, Auvergne, Luneau
Joined Aug 2008
81 Posts
Wire extensions for Motor

For the CL-415, I am using 2x Turnigy L2205-1350 Brushless Motors (100w) with a max current claimed to be 13.5A. As I wish to put the ESC's in the fuselage, I have to extend the 3 wires on each motor. These are now about 9cm long, and judging by their diameters, about AWG 16. Can I also use AWG 16 (if it exists) for the extensions? 3 x AWG12 wires are quite bulky, and I would obviously prefer the minimum size.
(I do have to extend all 3 wires?)
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Last edited by Bo43; Mar 08, 2012 at 11:24 AM.
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