View Full Version : ESC fail, crash, onboard cam
10-09-2010, 05:18 PM
Sometimes I have the problem that one ESC fails in flight. In this video you hear the lipo mon beep one time, then quad crashes (was about 6 feet / 2 meters). on ground, you hear the ESC starting up again.
as it looked from ground it was motor 1 (front left) lipo was fully charged, but I guess 4400 15C is not enough power. is it possible that the ESC got low voltage...
ESC configuration: throttle range calibrated, break on, cutoff mode soft, cutoff voltage medium.
any ideas? don't want to kill more motors and props :P
10-09-2010, 05:24 PM
Maybe the ESC is bad - so exchange it
10-09-2010, 05:38 PM
that was my first thought, but its not always the same ESC. first it was rear left motor, after recalibrating all ESCs with the transmitter, no further problems with that motor. now it was the front left. maybe these towerpro 18A ESCs are just crap. I ordered a few hobbywing ESCs, maybe they are better.
but point is, you hear the lipo mon with one beep, indicating low voltage and in the same second quad crashes... that can't be a coincidence...
I had the EXACT same thing today and have had it before and I am 100% certain of what it depends on.
I have programmed in my 4 arm LED's to flash at 2Hz rate if battery voltage would ever come below 10V (on a 3S lipo). It started to flash in flight, and since my battery was so low C rated in conjunction with low capacity, it yields a big momentary voltage sink if the slightest throttle increase occurs. If the ESC's cutoff voltage is set to 9.7V maybe (I HAVE NO IDEA WHAT IT IS SET TO ON MY ESC'S!!!, its a crappy routine for setting it), they more or less completely shut the motor down. These routines are MADE FOR AIRPLANES since their stability is NOT dependent on RPM of the motors.
As a result, at the slightest voltage dip, the quad looses all possible stability.
This can however be remedied by a high C/high capacity battery that don't make voltage dips when "overloaded" as much as the weaker batteries. This and recalibrating the cutoff voltage (best I can, estimate, sometimes with 2S battery just for calibration) has made my platform stable ever since the battery change.
However, I was so ********** stupid to fly with a really weak lipo today, on a big flying day on a heli airfield. I got so embarrassed, still having the big lipo in my trunk and lost 2 props the first flight which lasted less than a minute.
Here is the FPV live video:
But I got to fly a 600 size nitro heli with a .50 engine, so it was fine! :P Video of that is to come.
Then I made a stupid mistake once again this day, thinking my dad had learned something from both Phoenix training and getting to fly that monster nitro heli with a teacher. So I let him fly my quad with my last set of props. Result - cracked 12" prop and splinters popping out of our house exterior!
10-10-2010, 10:11 AM
yes looks exactly the same... I also found out that it's not happening when i fly 1-2 meters over ground for about 1 minute, land and fly again, and again. i think the landing is kinda regeneration break for the lipo and the voltage drops do not occur. 20C lipos are already shipped and I'll change cutoff limit, maybe that helps...
and to be honest, the lipo wasn't fully charged if I think about the flight again.... I was in air for about 4 minutes, high altitude flights, lot of wind... had 1-2 lipo mon beeps before but I thought the lipo is still okay... maybe I should not just ignore these beeps :D
10-10-2010, 03:56 PM
Flying any aircraft with only a 15-20c lip is really pushing your luck. Keep in mind you are pushing not 1 but 4 motors.
If you run a 2000mah lipo at only 20c, (or less) and you have 4 motors capable of pulling say 15amps under full power, the battery is only capable of discharging 40amps, and you are trying to pull almost 60amps, of course there are going to be issues. Places like Hobbyking have high discharge rate batteries for so cheap, you should never be running anything less than a 30-40c pack, why risk it.
If you think about it, if you are running 4, 18amp escs, you are creating the potential for upwards of a 72amp draw. So the smallest pack you would want to run is a 25c, 3000mah pack to get at least the ability to dump 75amps.
What I measured earlier, normal flying on KDA and other motors are around 4-7 amps / motor and mostly is closer to 4 amp than 7 especially if you run them with 10x45 size props. Overall current is around 20Amp that you need.
Usually 20C should be enough. Tho it does not harm to have 25-30C's
10-10-2010, 05:21 PM
thanks for the feedback. I know the 15C is a bit risky, it was in the tutorial, that's why I bought them. I ordered 4000 / 20C, now.
but I don't think anymore it's the problem I got. Today I was flying for about 25min, 1-2 meter over ground cause I didn't want to risk more motors and props :) nice flying without any problems while in air. but when disarming and arming, some ESCs did randomly restarted (beep-beep-beep, beep). and sometimes arming was okay, but when applying throttle 1-2 ESCs restarted... I guess those towerpro ESCs are crap... or you guys got an other idea what could cause this behavior?
what ESCs are you guys using? I know, turnigy plush, but they are unable to get at the moment, as you know. Any other recommendations? hobbywing? (I've already ordered a few of them).
10-10-2010, 09:44 PM
It's possible that you have a weak connection somewhere. Maybe go through all the connectors, and all the solder joints and make sure they are all in good shape, and there are no cold solder joints. It's possible that you have a bad connection and the vibration is making it intermittently lose contact.
10-11-2010, 01:27 AM
This is why I have built a three axis gimbal that I can mount my quadrarotors on and see how they perform in relation to stability and run time. A test gimbal can save a lot of grief later.
10-11-2010, 01:42 AM
@TCIII - can you post a picture of this gimbal setup?
TCIII, that is probably a good idea, but you loose some of the real life environment characteristics, such as weight contra thrust contra power needed.
And a little different vibration characteristics probably.
Well, I always hold the quad in my hand with hover throttle before flying to ensure everything is ok and fly from my hand, WITH SAFETY GOGGLES ON!
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