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Jan 30, 2009, 01:47 AM
Registered User
CustomPC's Avatar
The LVC is set to 9.5v.

I've just realised i had a brain fade.

All my pre-purchase calculations and all the published data assumes a voltage of 10.5V and 380 - 400W.

My test runs were 100W more @ 500W because these Rhino 2350mAh 25C packs i have are holding 11.4V for several minutes.

I think the ESC is undersized for 500W and is going into current overload protection, so i need to remember to keep the throttle under max until i can afford to upsize the ESC to a 55A or 60A.

I let the pack run down some and when it got down to 10.5V under load i was seeing 350W to 360W
Last edited by CustomPC; Jan 30, 2009 at 02:33 AM.
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Jan 30, 2009, 10:32 AM
Glitch Master
Jim Varley's Avatar
Quote:
Originally Posted by CustomPC
The LVC is set to 9.5v.

I've just realised i had a brain fade.

All my pre-purchase calculations and all the published data assumes a voltage of 10.5V and 380 - 400W.

My test runs were 100W more @ 500W because these Rhino 2350mAh 25C packs i have are holding 11.4V for several minutes.

I think the ESC is undersized for 500W and is going into current overload protection, so i need to remember to keep the throttle under max until i can afford to upsize the ESC to a 55A or 60A.

I let the pack run down some and when it got down to 10.5V under load i was seeing 350W to 360W
Running a 3S (12.6 volts) X Amp capacity of ESC (45 amps) = 567 watts absolute max capacity of your setup.

I like to leave 20% wiggle room under the max rating which would be 454 watts max capacity for your ESC at 3S in my opinion, to account for heat dissappation, and longevity of your electronics.

I guess what I am saying is I agree with you wholeheartedly.

--Jim
Jan 30, 2009, 11:18 AM
Innov8tive's Avatar
Thread OP
Telemachus,

The 2208 motors are real powerhouses for their size, however, because there are probably twenty 450 size helis for every 400 size heli, they just do not get the "Airplay" that the larger HK-2221 motors get. For the 200 to 300 size helicopters, the HK-2208 motors are hard to beat!



CustomPC,

We tested the motors at 10.5 volts, because at that time, the average 3-cell Li-Po battery would load down to that value, and this gave a pretty realistic expectation of the true power you would get from the motor. If you were actually holding 11.4 volts under load, then you will get about 20% more power out of the motor.

If you get a solid red light, then that means that the temperature of the PC board is over 60 degrees C (140 F) during power-up. This will result in the ESC only going to half power to prevent the user from burning it up. If you are running a 45 amp ESC, you should limit yourself to a 13x6.5E prop to keep the current down to a safe level until you can upgrade to a 55 or 60 amp ESC.

As an Electrical Engineer, I always de-rate the electronics, and never run a motor or ESC at more than 75-80% of it's max rating. The same goes for batteries. If you never exceed 75% of the rated max current, and never pull more than 80% of the capacity from the pack each flight, they will last a long time.

Talk to you later!

Lucien
Jan 30, 2009, 11:29 AM
LaurenceGough's Avatar
Thanks Lucien for your description on the motor and 400 size, very helpful! (might just pick one up for my 400 too )
Jan 31, 2009, 02:06 AM
Registered User
CustomPC's Avatar
Quote:
Originally Posted by Innov8tive
CustomPC,

....... If you get a solid red light, then that means that the temperature of the PC board is over 60 degrees C (140 F) during power-up. This will result in the ESC only going to half power to prevent the user from burning it up.

Lucien
Lucien,

60 degrees seems like a low tolerance too me. The heatsink on the ESC was only warm to the touch. I know other brands cut power at 80 deg.

Is the high temp protection switched on/off with the current overload protection?

Also, does it only check for the high temp at motor startup or will it activate the protection in-flight if the ESC hits 60 deg.

My thought is that if i plug in my pack and fly the model and make sure that i never throttle back to zero by using throttle trim for an idle tick-over, will that stop the protection kicking in?

It's probably not the solution because the overheat protection was active even after leaving the ESC to cool for an hour, so subsequent flights would all be at half power.
Jan 31, 2009, 01:39 PM
Innov8tive's Avatar
Thread OP
CustomPC,

The 60C temp cutoff is for boot-up at the beginning of a flight. This would only happen if you were running back to back flights with only a few seconds of time between battery changes, without allowing the ESC to cool down first. In flight, the over-temp cutoff point is 90C or 194F, which should never be reached unless you are pushing the ESC way too hard, or have no cooling air provided.

In most cases, if you are getting the half-power issue with your ESC, it is due to the throttle endpoints not being set correctly. If you do not calibrate the throttle endpoints onthe Scorpion ESC's, you might get a condition where you cannot get full throttle. The other thing that will cause operation at partial throttle is running the ESC at greater than recommended current, or running too large a motor on an ESC, even if the motor is not pulling it's full rated current.

I have seen a couple cases in the past two years where a Scorpion ESC would kick in the over current protection a bit too early, due to a component that was out of tollerance, but this is very rare.


For everyone else:

People need to understand that Scorpion ESC's are built different from other brands on the market. Most other ESC manufacturers build their speed controllers with no safety back-ups at all. The user is free to run the speed controller at greater than the rated currnet as long as they want, and if they push it too hard, the ESC goes up in a ball of flames.

After seeing this time and time again, the Scorpion designers decided to take a different approach. Instead of allowing the user to burn up ESC's, either on purpose or by mistake, Scorpion chose to add over-current, over temperature and short circuit protection in their ESC's to prevent this.

Where the problem now arises is in users that are used to running their other brand 60 amp ESC at 65 amps all day lond, find that the Scorpion 60 amp ESC shuts down, and figure that "There must be something wrong with it". In actuallity, the ESC is doing exactly what it is designed to do, prevent the user from accidently damaging the ESC.

I have gone over this several times before, but I think that it is time to bring it up again, "Never Push Electronic Components to 100% Duty Cycle, EVER!" The ratings on electrical components are not like speed limits that can be exceeded without care or worry. The voltage and current ratings that are placed on components are there to let you know that if they are exceeded the part WILL be damaged. In might not catistrophically fail immediately, but it will be damaged. This damage might not cause the part to fail until later, but rest assured, it will fail.

I worked as an Electronics Technicial and later as an Electrical Engineer with several government electronic companies. Whenever we built anything for the government or military, we could not exceed 50% of the rating of any part. This meant that we could run no more than 25 volts through a 50 volt capacitor, or more than 5 amps through a transistor rated for 10 amps, or 0.5 watts in a resistor rated for 1 watt. This insured that no component in the system would be over stressed and cause a failure of the assembly.

In commercial engineering, most people will not use more than 75% of the rated capacity of an electronic device. This is a very good practice, and should be heeded in our modeling ventures as well. Unfortunately, most people treat the voltage and current specs on parts like batteries, ESC's and motors like speed limits, and figure that if an ESC is rated for 55 amps, running it at 65 amps every once in a while won't hurt. Granted, it is normally OK to run products up to the max rating for short periods of time, but the overall running condition should be kept below that.

In a nutshell, I like to use the following guidlines for components:

Motors: Prop them to run at no more than 80% of the maximum rated current or power for continuous operation. For 3D type planes, where full throttle is only used in short 5-10 second bursts from time to time, running up to 100% rated current is OK, since most of the flight is run at 50 to 60% power. This would mean that if you have a motor rated for 50 amp max, don't run it at more than 40 amps. Likewise, if it is rated for 1000 watts of power, don't push it to more than 800 watts.

ESC's: Size them to be able to take, at a minimum, the maximum rated current of the motor, or so that the current drawn at full throttle is no more than 75% of the rated current for the ESC, whichever is higher. For example, if you have a motor that draws 60 amps at full throttle, use an ESC that is rated 80 amps.

Batteries: Size them so that you never pull more than 75% of the maximum rated current at any time, and never pull more than 80% of the rated mah capacity from the pack. In this case, let's assume you have a 2000mah 20C 3-cell Li-Po battery. At 20C, the max current for the battery would be 40 amps, so I would recommend not running this battery at over 30 amps of current draw. Also, you should not pull more than 1600mah of energy from the battery during each flight. By doing this you can easily get 100 cycles or more from your Li-Po batteries. If you exceed these values, don't be surprised when your batteries start going south after only 25 flights.

Hopefully that helps people understand the electronics a little better. Since I have worked with electronics for the past 35 years, there are a lot of things that I just take for granted that many other people simply do not know or understand completely.

See you later!

Lucien
Jan 31, 2009, 01:46 PM
Registered User
Dr Kiwi's Avatar
A wonderful voice of reason, Lucien!

I keep saying the same thing (as does Louis Fourdan!) but no-one seems to listen to us.

Now if only that small part of the RC hobby gang (the ones who regularly advocate over-cooking everything) would just show due prudence... we would all be happier, and not have to explain, again and again, why someone's 300W motor cooked when they put 600W though it... surprise, surprise!
Jan 31, 2009, 08:18 PM
Firefox
Firefox675's Avatar

Scorpion HK-3026 V2 reduced shaft


Does anyone offer a replacement shaft for the Scorpion HK-3026 motors that has the end reduced to 1/8th inch (3.17mm) ?

thanks
Randall
Jan 31, 2009, 09:21 PM
Hey Ya'll!! Watch THIS!!
Michael Paxton's Avatar
Little Screamer 1400 is a 5mm with a 3.2 or 3.17 end. You can check with them.
(You may have to make your own flats and cut the length down though)
~M~
Jan 31, 2009, 09:46 PM
still charging
still charging's Avatar
I may have missed the "time and time again" posts on these facts Lucien posted, but I did in fact read them individually for each component in the million forums I search for specific advice. I'd just like to thank you for restating these very important facts about operating electronic devices Also, I'd like to say that the scorpion 2221-8 is AWESOME!! And the programing of the ESC's is top notch, not to mention the functionality and safety features (which I didn't even know about over current protection, very cool!). This hobby just gets better and better, lol. Now if only it could get me to work >.>

-Joe
Feb 01, 2009, 08:12 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
One addition to Lucien's excellent post:
Reducing throttle only reduces the average current, it does not reduce the maximum current in the current-pulses. A controller is always full-on, and at part throttle the current is chopped in smaller chunks. See these pictures
http://www.aerodesign.de/peter/2001/...DY-BL_eng.html
-> partial load

Vriendelijke groeten Ron

phase voltages at partial load
Feb 02, 2009, 03:36 AM
Registered User
icrashrc's Avatar
Does Scorpion have a close replacement to a Mega 16-15-5? I'm trying to turn a 8" or 9" folder on 8 NiMh cells and the Mega looks about right but Scorpions are less expensive and easier to purchase. Thanks!
Feb 02, 2009, 04:48 AM
Registered User
Fourdan's Avatar
Quote:
Originally Posted by icrashrc
Does Scorpion have a close replacement to a Mega 16-15-5? I'm trying to turn a 8" or 9" folder on 8 NiMh cells and the Mega looks about right but Scorpions are less expensive and easier to purchase. Thanks!
Hi
IMHO not because desired Kv = 1800 + weight 76g + Rm ~ 0.068 ohm (??)
S2215 have lower Kvs
HK2221, HK2216 have higher Kvs

If you want Kv around 1800 (keeping voltage and prop) you have that stock outrunner (not a Scorpion)
Dualsky XM 2834CG-14 Kv 1800 weight 66g (a little less poweful) Rm 0.098 ohm

I have placed a question mark regarding Mega Rm = 0.068 because sometimes Mega indicates only half the Rm, and I have not tested this 16-15-5
Of course dimensions and mounting are different

Another solution is to take a kit and custom windings to get your desired Kv

Louis
Feb 02, 2009, 06:44 AM
Southern Pride
everydayflyer's Avatar
Quote:
Originally Posted by Dr Kiwi
A wonderful voice of reason, Lucien!

I keep saying the same thing (as does Louis Fourdan!) but no-one seems to listen to us.

Now if only that small part of the RC hobby gang (the ones who regularly advocate over-cooking everything) would just show due prudence... we would all be happier, and not have to explain, again and again, why someone's 300W motor cooked when they put 600W though it... surprise, surprise!
Sounds like you have been thinking of me Phil

My CC Phoenix 60 , Scorpion 3020-12 / APC 12X8E / Thunder Power Pro Power 40C 4S 3300 was checked after a 7 min. flight and the numbers were.

Battery as flown not recharged.
990 watts peak ( 940 staedy) 13.16V min. / 74.18 amps. / no load V after test 14.73.

FYI A total of 2855 mAh was used from the battery and only 2725 of in in the 7 min. flight so in flight average was 23.35A which would be close to 335 watts and WOT was only reached twice and for no more than 2 seconds each time. Also that Scorpion motor now has 280 flight on it and past flights were with 600 to 850 watts setups, I just went with a much stronger power source.

What can I say I like to push the envelope as in over 1,000 watts on a 58 oz. AUW sports plane. If I cook the motor Dan will rewind it and if I smoke the ESC CC will replace it for 1/2 price. My Scorpions never even get warm when being pushed like this and I have never had a CC Phoenix to trip the over current sensor which I leave set to default setting.


Charles
Feb 02, 2009, 08:28 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by Dr Kiwi
A wonderful voice of reason, Lucien!
I keep saying the same thing (as does Louis Fourdan!) but no-one seems to listen to us. Now if only that small part of the RC hobby gang (the ones who regularly advocate over-cooking everything) would just show due prudence... we would all be happier, and not have to explain, again and again, why someone's 300W motor cooked when they put 600W though it... surprise, surprise!
Shouldn't the manufacturers do the de-rating?

Vriendelijke groeten Ron


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