Hi all,

2 weeks ago I flew my Mavic Pro in the Swiss Alps, cloudy and foggy day, around 0 Celsius. After a few minutes of slow flying I frist to 'motor current error' and shortly after 'battery overcurrent' warnings. I immedialy initiated RTH and since the landing seemed very fast, I tried to this on manual, but the drone crash landed.

One arm was bent up and showed the interior wires, so I initiated a repair ticket since I took Care/Refersh when I purchased the Mavic.

Within days I received a UPS label, sent the drone in and was quoted a few EUROs less than my own Refresh contribution would have been. Since the drone is over half a year old and the coverage was less than half a year remaining I opted for replacement, but I also asked DJI to check my flight records.

I paid my contribution since I wanted the drone back before the Easter weekend. The day after DJI support told me they could not do a data analysis on repairs that were paid already. Bummer but ok - but I want to know what the story is on my crash - more for learning than anything else.

I found out that this type of issues happened before on foggy days around freezing and that the props might have suffered from icing issues. Understandable if that is indeed the truth.

Anyone wants to have a go at my flight record ?

I suggest post the flight records here and some of the experts will look at it and give feedback. from looking at other posts here it is not recommended to fly in very cold weather but some guys have flown and had no issues, what phone were you using by the way?

When I fly in cold weather, I try my best to keep my drone as warm as possible until takeoff. I do most of my pre flight check inside and then taking the drone outside to lift off or if I'm in a car, I'll attempt to do as much as I can in the car before taking it outside. But it appears in the Swiss Alps that both of those options probably aren't able to be done by the looks of it. I've never had any errors for temperatures and I'm eager to see how this turns out.

  I can also post the flight records, but I don't know where those should go....

Please upload your flightrecord to this site and share the link with us if you wish so: http://www.phantomhelp.com/LogViewer/Upload/
It gives much better data to analyse.

Yep, it will be easier to read from Phantom Help

A CW Posted at 2018-3-28 12:39
Yep, it will be easier to read from Phantom Help

thanks - http://www.phantomhelp.com/LogViewer/GHZ7DB7SBTSWC0RJXQGB/ here the log is

fans08f0747b Posted at 2018-3-28 13:38
thanks - http://www.phantomhelp.com/LogViewer/GHZ7DB7SBTSWC0RJXQGB/ here the log is

Sorry to see this - Despite a good start to the flight with 14 satellites in P-GPS mode on take off you'll notice that your battery power dropped 7% in less than 28 seconds at the end of the flight (and only 10% in the first 2+ minutes)... You had a battery overload error. Essentially the sub zero temperatures would have caused the battery power to deplete too rapidly in line with the motor current and this caused speed errors too - were you using full throttle down when landing/during the flight? From my perspective the motors basically cut out in the final seconds as the battery could not sustain enough power to the ESC's to maintain position. The cell deviation is relatively OK. When you see the 'motor overload warning' you need to be very gentle on the sticks. What temperature was the battery when you took off? It needs to be at least 15c though closer to 25c would be better. Was it also a windy day? Strong winds can make 0c feel like -10c.
Bottom line- my guess is that the environment you flew in was too cold for the batteries, they were too cold on take off and you were perhaps too heavy on the throttle/pitch during flight and the batteries failed to maintain enough power for the ECS's to control motor speed effectively and the drone crash landed - I could be wrong of course but that's the most likely explanation from what I'm seeing.

Hi there, I'm sorry to hear about the issue that you have experienced. Please take good care of your drone and do not fly it at a very low-temperature environment, the recommended operating temperature range for the Mavic pro is from 0° to 40° C, you can check it from the website: https://www.dji.com/mavic/info#specs. Thanks for your support!

A CW Posted at 2018-3-28 14:25
Sorry to see this - Despite a good start to the flight with 14 satellites in P-GPS mode on take off you'll notice that your battery power dropped 7% in less than 28 seconds at the end of the flight (and only 10% in the first 2+ minutes)... You had a battery overload error. Essentially the sub zero temperatures would have caused the battery power to deplete too rapidly in line with the motor current and this caused speed errors too - were you using full throttle down when landing/during the flight? From my perspective the motors basically cut out in the final seconds as the battery could not sustain enough power to the ESC's to maintain position. The cell deviation is relatively OK. When you see the 'motor overload warning' you need to be very gentle on the sticks. What temperature was the battery when you took off? It needs to be at least 15c though closer to 25c would be better. Was it also a windy day? Strong winds can make 0c feel like -10c.
Bottom line- my guess is that the environment you flew in was too cold for the batteries, they were too cold on take off and you were perhaps too heavy on the throttle/pitch during flight and the batteries failed to maintain enough power for the ECS's to control motor speed effectively and the drone crash landed - I could be wrong of course but that's the most likely explanation from what I'm seeing.

"Bottom line- my guess is that the environment you flew in was too cold for the batteries, they were too cold on take off "

Good catch.

I was watching a video of guy attempting to break some sort of racing drone speed record.
Anyway, he flew back and forth a couple of times, then several circles, before attempting the run.
He mentioned that batteries needed to be warmed-up before being pushed to their limits.  Which the props and motors he was using would do.

The log files showed that battery temp were 20°C at start and went up to 30°C at the end of the log.
So, battery temp were not the issue here.

The logs showed a slow, but steady increase of Amps being drawn from the battery.
This were in no correlation to the fly state the aircraft was in. (I.e. sport mode, or other 'aggressive' flying style)

Then more Amps being drawn, hence props RPM were increasing, at one point the message 'battery overcurrent' popped up.
This could indicate prop icing. Icing results in slowly decreasing lift and increasing drag, the flight controller tries to counter these effects but at some point the ESC's maxed out.
Due to the fact that the props could not produce enough lift to keep the aircraft in the air, then gravity took over ...

The OP itself came to the conclusion, that icing could be an issue here.
More details on that incident can be seen on the .DAT files on the phone/tablet.

Keule Posted at 2018-3-28 22:29
The log files showed that battery temp were 20°C at start and went up to 30°C at the end of the log.
So, battery temp were not the issue here.

thanks - I was wondering - looking at https://forum.dji.com/thread-141848-1-1.html

Should I upload a DAT file too ?

Keule Posted at 2018-3-28 22:29
The log files showed that battery temp were 20°C at start and went up to 30°C at the end of the log.
So, battery temp were not the issue here.

The drone was in active track and intelligent flight modes drain the battery almost as fast as sport mode. The fact that the flight is 2.5 minutes long in 0c I would be very surprised if ice formed on the props that quickly LOL - I've flown my drones for over an HOUR at that temperature with no ice on my props. Also, as I stated, the battery dropped 7% in 28 seconds from 2 minutes after take off and battery over current is caused by temperature conditions.

A CW Posted at 2018-3-28 23:34
The drone was in active track and intelligent flight modes drain the battery almost as fast as sport mode. The fact that the flight is 2.5 minutes long in 0c I would be very surprised if ice formed on the props that quickly LOL - I've flown my drones for over an HOUR at that temperature with no ice on my props. Also, as I stated, the battery dropped 7% in 28 seconds from 2 minutes after take off and battery over current is caused by temperature conditions.

again, thanks - but if you look at the Jungfrau-joch post - I linked before - that was even much colder

fans08f0747b Posted at 2018-3-28 23:47
again, thanks - but if you look at the Jungfrau-joch post - I linked before - that was even much colder

I get that but I find the temperature readings very subjective too - in all the years I've been flying I have never seen a battery temperature increase 10c in 2.5 minutes, especially when flying at 0c. I took off the other weekend in -1c conditions and the battery was 18c on take off and after a 25 minute flight my battery temperature was still only 27c upon landing. This could also be caused by the VPS failing as unable to detect the ground if covered in snow but the most likely explanation is that the temperature prohibited the battery performance to power the ESC's to drive the motors and the errors that are listed support that which DJI Diana has also supported as the most likely cause.

A CW Posted at 2018-3-29 00:07
I get that but I find the temperature readings very subjective too - in all the years I've been flying I have never seen a battery temperature increase 10c in 2.5 minutes, especially when flying at 0c. I took off the other weekend in -1c conditions and the battery was 18c on take off and after a 25 minute flight my battery temperature was still only 27c upon landing. This could also be caused by the VPS failing as unable to detect the ground if covered in snow but the most likely explanation is that the temperature prohibited the battery performance to power the ESC's to drive the motors and the errors that are listed support that which DJI Diana has also supported as the most likely cause.

I looked again at the logs and the battery temperature readings were indeed ranging from 20.9°C to 33.°C within ~ 152 seconds.
Airdata reports ground weather temperature: 0.4°C / dewpoint -1.4°C

Keule Posted at 2018-3-29 11:56
I looked again at the logs and the battery temperature readings were indeed ranging from 20.9°C to 33.°C within ~ 152 seconds.
Airdata reports ground weather temperature: 0.4°C / dewpoint -1.4°C

Interesting to see - that's a massive increase in battery temperature in such a short period. Perhaps the battery was faulty from the outset.

Well, I still have that battery - the Mavic was replaced by DJI.

Should I contact them about the battery and have it replaced.

But in that case this should not have been a Refresh Care issue but a warranty issue or.... ?