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Old Jan 08, 2013, 02:02 PM
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Multirotor accident causes.

I just crashed my quadcopter last sunday taking pictures and videos of the Dakar race here in Peru. I am not 100% sure of the cause of the accident.
First this is my configuration:
radio: turnigy 9x with Frysky module with telemetry onboard
frame: HK X666
FC: DJI NAZA
MOTORS: turnigy xp 3530 kv1100
ESC: HK blue series 30A
PROPS: SF 10x4.5
fpv: 5.8 500mw
battery: nano tech 3S 2.65 35-70C AND nano tech 3S 2.2 25-50C
flight time:5min with the 2.2 and 7min aprox with the 2.65

with gimbal and samsung NX1000 camera flight time is 3 with the 2.2 and 4 min with the 2.65.

Well I have flown more than 100 times my quad with no problem, but this last weekend I wanted to take alot of photos of the race so I bored 5 old batteries to a friend.... (turnigy 3S 2.2 20-30C) . I made my first five flights with my batteries with no problem at all, and then I put one of this old batteries wich I charge and balance the day before and mount it on the quad... after a minute aprox the quad turn OFF (everthing, motors, radio signal, fpv) and went down like a rock to the ground. So ok I fist thought the problem is the battery.. but why? when I when to the crash site, the quad was powered again, the naza was blinking , the fpv TX was on... so maybe for I second the power went off and that is enough for the quad to crash because it takes somes seconds to initiate the motors again..
I checked the battery and it hade 11.65V . and all cells were close to eachother in there volts... So what could happend? or maybe another thing went wrong and just a coincidence that was with that old battery. Maybe the current supply from the battery wasnt enough (2.2A x 20C= 44A) this motors pull 22a each at full power so 88A PLUS naza, fpv TX, gimbal servos. but can that make the battery sudently stop giving power???? because off the heavy weigh off the equipment for a small quad and heavy wind (15 knots aprox)

hopefully the dakar race was in the desert so not too much damage happen to the quad, the naza and camera are OK, I just bend 2 motor mounts , one arm and broke one gimbal servo.

I will like to know if an old battery can fail with no worning. I am builing again the quad and trying to get rid of the sand in side the motors and try again that battery holding the quadcopter and wait it to fail...I it dosent... I am in trouble.
I'll like to hear some hipotesis

thank you very much .here are some pics from the race
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Old Jan 08, 2013, 02:11 PM
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Germany, HE, Darmstadt
Joined Jun 2012
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I'm pretty sure the battery power was your problem here. If the battery is only rated for 30C peak discharge, it's plain not enough for your motors: 88A peak + overhead from electronics will need at least ~40C from a 2200mAh battery. This is why it works fine with your batteries (35-70 and 25-50C), but not with your friend's ones. I am not sure what happens when the currect drawn from the battery exceeds its discharge rate by so much, but I would think the voltage will drop significantly, probably below the hard cut-off value of the ESCs, which will turn off the motors and drop your quad out of the sky.
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Old Jan 08, 2013, 02:45 PM
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United States, MA, Sudbury
Joined Aug 2006
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What are your ESC's brake settings and low voltage cutoff set to?
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Old Jan 08, 2013, 03:03 PM
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I never change the settings of my ESC , the default settings are:
brake: OFF
battery type detect: LiPo with auto cell
Low voltage cutoff threshold: Medium (3.0V/60%)
Timming setup: Automatic
Soft acceleration start up: soft acceleration
governor mode: RPM OFF
Frequency: 8kHz
Low voltage cutoff type: reduce power

after the crash I checked the battery with my voltimeter and it was at 11.7V (3.9 V each cell) thats far away from the Low voltage cutoff, no even the NAZA first protection warning went on (wich makes blink red the led) or the second one that makes the quad land alone when it reach 10.5 volts.
Maybe the battery for a second went onder 3volts and the come back??
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Old Jan 08, 2013, 03:09 PM
pm1
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Joined Oct 2008
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At first sight, it looks like the battery....

If you say, that your fligth time is normally 3 minutes with a 2200 mAh battery, you pull out about 40 amps on *average*. If you have a "normal" battery supplier like hobbyking, which is lying about the rate of his batteries, you can be sure, that you have overloaded the battery, especially when it was older. Btw. a simple lipo beeper would have indicated the problem.

but...

What doesn`t fit into this picture is, that the fpv has shut down in the same second.
This doesn`t fit with the assumption of the power cut off of the ESCs, too. If the ESCs had switched off the motos, there would have been plenty of power for the fpv transmitter...
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Old Jan 08, 2013, 03:15 PM
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Hi pm1, I wasnt watching the monitor at that moment , I was looking directly to the quad, dident see if the fpv went off . BUT my radio made a beep, that happens when it losses comunication with the RX (frysky telemetry) it is two way. It was a total shut down
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Old Jan 08, 2013, 03:55 PM
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Easiest answers are mostly the correct ones as well.

In this case - if the only thing you have changed is battery, then to about 99% that was the reason of fail. Might be even bad contact or too high discharge...
Especially when you say it was in desert, I'd guess that temperature might be high as well...

If your quad flies well with your own batteries, I wouldn't bother searching further.
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Old Jan 08, 2013, 05:00 PM
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Yes thats true, Just not convince in the way it happend, When I got to the quad on the ground it was on again, the fpv, the naza, the reciver, it was like a 1 second shutdown..

I will rebuild the quad this week ,(having a hard time finding how to open the motors to clean the sand) and I will but the same battery and hover above a matress of some like with the same weight I did sunday I see what happens..
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Old Jan 09, 2013, 02:27 AM
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One more thing to mention, is you shouldn't have your ESC's programmed as LiPo. The last thing you want is for your ESC's to shut off on low voltage, you want a low voltage alarm to be making loud noises so you can land safely.

Most people recommend setting the ESC's to Ni-XX and setting cutoff voltage to low.

Even if you can't hear the voltage alarm it's better to kill a battery than have your copter fall from the sky. A good thread about it is here

http://www.rcgroups.com/forums/showthread.php?t=1384846

As has been said, it was likely the battery, the reason it would have been on again on the ground is because you were no longer pulling current from the battery and so it was back within spec and would have been supplying good voltage. Pulling over spec of the battery will result if a significant voltage drop (and possibly damage the battery itself). This drop would have caused your ESC's to shut down
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Old Jan 09, 2013, 10:19 AM
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Quote:
Originally Posted by WendoNZ View Post
One more thing to mention, is you shouldn't have your ESC's programmed as LiPo. The last thing you want is for your ESC's to shut off on low voltage, you want a low voltage alarm to be making loud noises so you can land safely.

Most people recommend setting the ESC's to Ni-XX and setting cutoff voltage to low.

Even if you can't hear the voltage alarm it's better to kill a battery than have your copter fall from the sky. A good thread about it is here

http://www.rcgroups.com/forums/showthread.php?t=1384846

As has been said, it was likely the battery, the reason it would have been on again on the ground is because you were no longer pulling current from the battery and so it was back within spec and would have been supplying good voltage. Pulling over spec of the battery will result if a significant voltage drop (and possibly damage the battery itself). This drop would have caused your ESC's to shut down
when the ESC low voltage cutoff is on, it cuts the power to the motor and to the recevier? thru the BEC or just the motor? because when it happend and the quad was falling down from the sky I lost all motors and signal from the reciver's telemetry to the module in the radio.
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Old Jan 09, 2013, 10:40 AM
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The way my power is distribute: the battery is conected to a distribution cable that I made with 5 ends, 4 for the ESC's and 1 for the naza (the naza gives power to the reciver not the ECS's). Later on I put a fpv tx wired to one of the ECS's connectos to power it.
So... when I lost power and the quad started falling down I didndt just lose power from the motors, I lost signal from the receiver( telemetry) wich does not recives power from the ECS's.
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Old Jan 09, 2013, 11:24 AM
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Quote:
Originally Posted by claudiovast View Post
The way my power is distribute: the battery is conected to a distribution cable that I made with 5 ends, 4 for the ESC's and 1 for the naza (the naza gives power to the reciver not the ECS's). Later on I put a fpv tx wired to one of the ECS's connectos to power it.
So... when I lost power and the quad started falling down I didndt just lose power from the motors, I lost signal from the receiver( telemetry) wich does not recives power from the ECS's.
I'm just learning how to set these things up but if I look at the wiring diagram that comes with the DJI WKM it looks like power goes though something called a PMU then through the ESC's then the controller and finally the receiver. But from your description it sounds like the controller has a separate supply so then it can only be a problem with the actual battery or it's connection.
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Old Jan 09, 2013, 12:07 PM
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It would depend on the ESC, I would have expected the BEC circuit to be separated completely so it shouldn't. In saying that, a BEC requires a certain input voltage to be able to function, depending on how large the voltage drop was it may have fallen underneath that threshold
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Old Jan 09, 2013, 02:35 PM
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I cut off the middle wire (the red one, because my ESC are BEC ) so no electricity is given to the naza, the naza pull power directly from the batery, thats why when you buy a DJI Combo (frame motor escs) the esc's are OPTO (they just recive signal from the reciver\FC, but not supply current)
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Old Jan 10, 2013, 06:32 AM
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could be a thermal shutdown? since your using a 10 inch prop on a 1100kv. i think your maximum prop size would be a 9inch.
just my opinion, i maybe wrong ..
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