Now with data: Hobbyking SS 25A esc works great it was my fault for not testing first - RC Groups
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Mar 09, 2011, 12:41 AM
expert noob
handyfella's Avatar
Discussion

Now with data: Hobbyking SS 25A esc works great it was my fault for not testing first


**Data for amperage test and motor/esc temps recorded a few posts down:

Alright, so I have this great foamboard low wing plane i build with a kf wing and a 2" foamboard square tube for the fuse and auw is ~24oz using an 1800 3s. I have crashed this plane so many times and it just fixes right up and flies like new everytime... Good it was this one with motors dying on I guess..

So i robbed the esc from this plane for the flying wing project and put it on the shelf awhile, and today I decided to stick this hobbyking esc and a bigger motor on the plane and dust it off for a little more fun since my flying wing needs the hinges reworked..

So I was using a hobbywing 18A esc with an alpha 370 motor good for about 24oz of thrust with a 9x4.7 prop on 3s and this motor flew the plane great several times no problems with the motor or the 18a esc..

I figured the alpha 400 920kv (150w) would be a little stronger and turn a 10x4.7 just fine and boy did it ever, it was doing inverted loop outs and pulling over the top etc, and then I was tooling around inverted and POOF, a little white puff of smoke out the front and I'm deadsticking inverted for a gentle glide down on it's canopy (motor died about 10 ft off the ground luckily) and i didn't attempt to try and roll it while gliding deadstick inverted that close to the ground, I just gave it tons of down elevator to keep it level and it didn't even break the prop or anything else for that matter.

Soooo... I came home and put my old 370 motor back on it as I finally got the cg worked out on this plane for the first time and it was flying awesome, and is totally scratchbuilt from no plans, so it was a little exciting to finally have it flying like I wanted..

Went to an empty well lit parking lot as it just turned dark, and fired up the plane again with a 10x4.7 cut down to about 9.3x4.7 and it has flown on an apc 9x4.5 several flights no problem at all.

So I'm looping a few times (ok once) but mostly just fly turn fly turn along the parking lot lights and then I'm in a turn just headed back toward me, and POOF, the magic smoke yet again!!??? Not any wot or crazy climbing, not even a little, and throttle was back to about 65% for most of the flight, I even checked by flooring it a few times and then backing off a little just to be sure I wasn't maxing it out.

Yet another dead stick, but very manageable and landed it like a pro, sort of, and only had minimal landing gear damage as it was really made to land very very softly (just weak landing gear in need of a redesign) but man that's 2 motors now, I have another 400 920kv and just ordered a few more motors but I am very reluctant to use this hobbyking esc on anything else that I own as I have just not had this issue with any other esc with this motor.

As a sidenote I have that volcano series 18A in my flying wing running a 175w alpha 450 890kv on 3s and it flies all day long with a 12x3.8 apc prop. It just doenst make sense that the 400 motor couldnt handle a 10x4.7 in my mind at all.. Don't understand it at all, as others even report using the 400 920kv motor with up to a 10x7 or 6 one of the two.

Does anybody have any idea what might be the problem??

Does this happen with some esc's where they just kill motors that worked great on other esc's? BTW the one I have is the hobbyking 25-30A SS non card programmable, and was like $6 or so..

It may be important to know that I didn't ever consider trying to program in the throttle range input, to show the esc the stick range from 0 to 100% throttle, so that makes me wonder if it was flying at wot even though i was at 50% stick, which if that is the case, it is very likely that killed them, as I know the 370 will get very warm at wot with a 9x5 definitely and the 400 is the same can diameter just a little longer and a bit torquier.

Thanks for any advice or input whatsoever. It was a pretty stressful day flying with all my motors dying!!
Last edited by handyfella; Mar 10, 2011 at 02:44 PM.
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Mar 09, 2011, 01:09 AM
The 6 P principle works for me
elecfryer's Avatar
Quote:
Originally Posted by handyfella
Thanks for any advice or input whatsoever. It was a pretty stressful day flying with all my motors dying!!
Well............although I do not know enough about your motors my first point is still going to be that esc's and batteries for that matter do not force electricity into motors, motors draw in electric. By placing a larger load on a motor it may draw in more electricty. A more efficient esc or "better" settings on an esc may also allow a motor to draw in more electricity.

Best point to point out, you tried a different set-up and apparently did not check any static (measure amp draw, voltage under load, rpms while holding the plane still) numbers. If you do not know what your motor system is doing prior to flight then IMO you have no right to expect success in the air although you could certainly hope for success!

Quite often when performing a maiden flight or first flight out of re-build, many people will underprop a plane just to provide a safety margin until they KNOW what is going on with their plane's propulsion system.

Oooops......almost forgot, lack of cooling is also a motor killer!

Michael (if your not fryin, your not tryin!)
Mar 09, 2011, 01:24 AM
expert noob
handyfella's Avatar
Well I certainly do plan to build a decent watt meter using a cheezy dmm from harbor freight though I sure haven't yet but I certainly have done some static testing and determined that even with the smaller esc it was delivering enough current to the motor under wot to cook it if run that hard long.

But my main question is really about this esc as to how you're supposed to program in the max and min throttle range as I totally forgot to do that. I do recall powering it up with the tx set to about 40% throttle and then setting it to zero and I have a hunch that this set the range far too narrow.

This of course would be my own stupid fault BUT when the esc came with absolutely zero documentation that could be the true culprit there. Its not so cheap to buy a $6 esc if you have to kill $30 in motors to learn your preliminary needed programming steps.

Thanks Michael
Mar 09, 2011, 01:52 AM
The 6 P principle works for me
elecfryer's Avatar
most esc's will work out the hi throttle and low throttle settings. This means that for most esc's, you can not limit the hi throttle setting, other than not advancing the throttle stick on the transmitter too far!

Typically we are better off starting with smaller props, getting the full power static numbers and then trying a larger or bigger pitch prop and recording those numbers as well.

Easiest trap to fall into, I was just doing what someone else said would work ok! It is always more work to check out your plane prior to flying it. It usually saves me from making a mistake or two, but not always! I have burnt up some good motors in my time!

P.S. the Turnigy watt meter is currently selling for $24!!!! It's a good deal!

Michael (if your not fryin, your not tryin!)
Mar 09, 2011, 03:34 AM
Registered User
Quote:
Originally Posted by handyfella
Well I certainly do plan to build a decent watt meter using a cheezy dmm from harbor freight though I sure haven't yet but I certainly have done some static testing and determined that even with the smaller esc it was delivering enough current to the motor under wot to cook it if run that hard long. ...
To paraphrase what Michael said in his first post, an ESC doesn't deliver current to the motor -- the motor demands how many amps it wants And how many amps it wants depends almost entirely on the prop size and characteristics, assuming your battery stays the same volts.

It's always possible that your ESC has a motor-busting fault in it, but it's much more likely that your motor is drawing too much current because it's over-propped. You need the wattmeter, or clamp-on ammeter, so that you can see what amps the motor's drawing with different prop sizes.
Mar 09, 2011, 04:37 AM
Registered User
lipoflyer's Avatar
Quote:
Originally Posted by handyfella
Well I certainly do plan to build a decent watt meter using a cheezy dmm from harbor freight though I sure haven't yet but I certainly have done some static testing and determined that even with the smaller esc it was delivering enough current to the motor under wot to cook it if run that hard long.

But my main question is really about this esc as to how you're supposed to program in the max and min throttle range as I totally forgot to do that. I do recall powering it up with the tx set to about 40% throttle and then setting it to zero and I have a hunch that this set the range far too narrow.

This of course would be my own stupid fault BUT when the esc came with absolutely zero documentation that could be the true culprit there. Its not so cheap to buy a $6 esc if you have to kill $30 in motors to learn your preliminary needed programming steps.

Thanks Michael
dont build a watt meter. i use this. http://www.hobbyking.com/hobbyking/s...dProduct=10080
Mar 09, 2011, 04:39 AM
Registered User
lipoflyer's Avatar
Quote:
Originally Posted by abenn
that your ESC has a motor-busting fault in it, but it's much more likely that your motor is drawing too much current because it's over-propped. You need the wattmeter, or clamp-on ammeter, so that you can see what amps the motor's drawing with different prop sizes.
i would think the motor was over proped and burned out. a cut down prop might have a bit more resistance at the egde of the prop which is also the fastes moving part of the prop
Mar 09, 2011, 08:29 AM
expert noob
handyfella's Avatar
No I will definitely be building a watt meter but thanks. I plan to keep the big planes on gasoline so small electrics is all I will be messing with. I'm pretty sure a stihl 25cc won't have this issue

Thanks for all the replies I will doing a check on throttle range as I am almost positive its the problem. The plane was just moving alot faster with this esc at any given point and if not the throttle setting it may just be the esc is allowing more current through with less resistance/impedance.

This has always happened near the end of a flight where the voltage is getting lower also and I know that some electronic devices demand more current as voltage goes down and this condition kills devices with tiny wires like these small brushless motors have. I may have been ignoring the lower voltage condition and pushing it harder too and it may have already been hot on top of that.

I agree about the cut prop btw. Im still a little mad that esc didn't include any sort of instructions not even a link to a website for cryin out loud!

Btw I am completely aware that batteries donít push current. They actually just deliver it based on impedance and their working voltage. I=V/R

I just didn't account for this esc delivering more current and that being problematic. :/
Mar 09, 2011, 10:15 AM
Registered User
Dr Kiwi's Avatar
I know that some electronic devices demand more current as voltage goes down and this condition kills devices with tiny wires like these small brushless motors have.

As Abenn has said, the motor/prop is what draws current from the pack, the ESC is just a dumb device which allows through whatever the motor/prop demands... if that is too much for the ESC, it fries. If the prop is too big, the motor fries (and maybe the ESC too).

Lower voltage will ALWAYS result in lower amp draw!!
Mar 09, 2011, 10:31 AM
expert noob
handyfella's Avatar
Yeah sorry I was thinking of a regulated device like an amplifier. Haha my own math shouldve told me that!!
Mar 09, 2011, 12:33 PM
Bipes Rule!
RITTMEISTER's Avatar

hobby king


Quote:
Originally Posted by handyfella
Yeah sorry I was thinking of a regulated device like an amplifier. Haha my own math shouldve told me that!!
I have ordered 4 motors/ESC from here I was told I have 45 days for delivery? It has already been 2 weeks now I get email 45DAYS? Did you wait that long? Is their stuff that poor quality? I heard after ordering you buy 3 motors and hope 1 works....
Mar 09, 2011, 12:53 PM
expert noob
handyfella's Avatar
I have had no problems until now using something other than a hobbypartz esc branded by hobbywing... The motors are powerful and very inexpensive.

I am testing my theory and will be swapping in a hobbypartz 12a esc to use with my last 400 series 920 to prove something right not sure what though. Will be using a 10x5 as normal as though everythings fine. Will do some static wot heat tests with ir thermo to be safe.
Mar 09, 2011, 01:03 PM
Bipes Rule!
RITTMEISTER's Avatar

Delivery


Quote:
Originally Posted by handyfella
I have had no problems until now using something other than a hobbypartz esc branded by hobbywing... The motors are powerful and very inexpensive.

I am testing my theory and will be swapping in a hobbypartz 12a esc to use with my last 400 series 920 to prove something right not sure what though. Will be using a 10x5 as normal as though everythings fine. Will do some static wot heat tests with ir thermo to be safe.
How long did you wait for delivery? Thanks Dennis
Mar 09, 2011, 01:24 PM
expert noob
handyfella's Avatar
Sorry, usually to Arkansas takes about a week once they send me the tracking #, so normally no more than 10-15 business days. Not too bad compared to waiting for hong kong shipping!

I have tested this setup with a dmm on the amperage setting (reads 10A max but I believe that is for 120v, so it can likely read well over 100A on a 12V system). I have another dmm to read voltage but my dummy light buzzer was plugged into the battery and the lights remained green which tells me the cells were staying over 3.7v under load, even at wot.

Test results: (measured today on the new 400 motor)

Amperage Draw:
at 60% throttle: 5.5A (where I was flying the other day) this reading was constant on my dmm measured inline across the negative terminal
at 100% throttle: 12.1A peak (<2sec) then drops to 11.8A, and I never sustain that throttle setting when flying but according to the specs this is within it's ability.

Motor and ESC temps:
Static 60% throttle sustained for 20 seconds or so:
Motor can: 115 F, windings 135F
ESC: 115F

That's with a cut down 10x4.7 prop (cut to 9.3x4.5) , so I think I found my problem, too much prop maybe? But the motor is rated to handle 10A continuous and 13A peak for 10s I think.
ESC is rated at 12A continuous and 15A peak, which I am getting nowhere near...

I will flight test it just to be sure. As static tests do seem to give hot readings compared to flight temps.
Last edited by handyfella; Mar 09, 2011 at 01:40 PM.
Mar 09, 2011, 02:09 PM
Registered User
I don't know what your problem is but I would advise getting a decent wattmeter that can show volts, amps and current.
They are pretty cheap now.

The SS esc's are being used by many people in tricopters and they have been found to be pretty good.

I have 2 tricopters which use 3 SS 25-30 Amp non-programmable esc's in each tricopter and they work fine.


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