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Mavic Air Forced Landing

spamgnome

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We can file this one under the category of, "I Never thought this would happen to me..."

Was flying my MA in farm country in Sport mode, and was just about to turn around to come home when I got the alert that the drone was landing due to a critically low battery. Good news and bad news...drone was recovered with no damage, but bad news is I had to trapse through 8' high corn for about 20 minutes. The Find my Drone feature worked perfectly!

What was unusual about this was that the "bar indicator" at the top that provides time remaining went from to the right of the "H" to blank in an instant...I verified this by replaying the flight in the Go4 app. The same replay shows the battery going from 36% to 0% also in an instant. The RTH feature also never kicked in. My question is WTF happened??? I've done several flights since, even on the same battery, but nada...all looks normal.

What troubleshooting steps should I take? I'd actually rather this be pilot error, but the behavior I saw leads me to thinking this is a bug.

Thanks for the help. Here is the recommended details

Problem? SEE ABOVE

Was unit in a crash? SORT OF...FORCED LANDING

What have you tried so far? REPLAYED FLIGHT IN GO4 APP

What device are you using ( iphone , ipad, Samsung , etc)? SAMSUNG S8 ACTIVE

What firmware are you running ( aircraft, remote controller)? MA, LATEST FIRMWARE

What Go app version are you using? 4

Any modification?
(if so what) NOPE

Did you change anything or install any apps? (if so what) NO

Do you have a video or pictures of the problem? (if so post link) Screenshot_20190902-112135.jpg
Screenshot_20190902-112156.jpg
 
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Doppler

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You most likely had one of the battery cells collapse. This is the scenario I dread the most and why I go through my logs with a fine comb after each flight. You will have to upload the flight log to be certain as to what happened.
 
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spamgnome

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You most likely had one of the battery cells collapse. This is the scenario I dread the most and why I go through my logs with a fine comb after each flight. You will have to upload the flight log to be certain as to what happened.
Thanks for the reply. Where are these logs you speak of? I think the batteries, even though they are 8 months old, have maybe 40 cycles on them. I looked at Air data and saw some scary stuff there...is this what you are referring to??

2019-09-02_14-26-39.jpg
 

Doppler

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Yeah, that doesn't look good. The flight log is a txt file and you can find it in the DJI Go 4>Flight records folder in your phone/tablet. Or you can simply share the AirData link for that particular flight. The HD flight player under the Notifications tab in AirData will have details on the battery cell performances during the flight.
 

Whatever

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You can make a function button check battery cell levels or tap battery icon to make sure they are balanced after takeoff.

Also this video is good.

 

spamgnome

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Yeah, that doesn't look good. The flight log is a txt file and you can find it in the DJI Go 4>Flight records folder in your phone/tablet. Or you can simply share the AirData link for that particular flight. The HD flight player under the Notifications tab in AirData will have details on the battery cell performances during the flight.
OK, I think this is the link you're talking about...

 

Doppler

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OK, I think this is the link you're talking about...

Yep, that is the one. And you can see it clearly, cell 2 was struggling from the start. But around the 10 minute mark it collapsed thereby triggering the forced landing. You were lucky to have gotten your aircraft in one piece. I wouldn't fly with that battery again if I were you.


Screenshot_2019-09-04 Aug 30th, 2019 06 19PM General Drone Flight Log from DJI GO app, version...pngScreenshot_2019-09-04 Aug 30th, 2019 06 19PM General Drone Flight Log from DJI GO app, version...png
 
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spamgnome

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Yep, that is the one. And you can see it clearly, cell 2 was struggling from the start. But around the 10 minute mark it collapsed thereby triggering the forced landing. You were lucky to have gotten your aircraft in one piece. I wouldn't fly with that battery again if I were you.


View attachment 81022
Yeah, I saw that too. But AFTER that, the voltage actually appears to go back up. Weird. I've been combing through the Airdata logs and I actually see this mis-balance in one of my other batteries. In fact, it's been that way for a while, I just haven't noticed.
I guess at this point I'm wondering about cause . Do I have defective batteries? Do I contact DJI about this? If so, what's the best method?
Also, per the excellent video posted above, I think that the Go4 app should have warned me about the imbalance, right?

I actually DID fly with this battery again with no ill effects, but the logs still look as they do above.
Really appreciate all the assistance.
 
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Doppler

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AFTER that, the voltage actually appears to go back up
That happens. You were flying in Sports mode which puts more stress on the battery cells; soon as the mode changes out of sports in to landing, cell 2 is able to recover somewhat. But what is important here is the fact that cell 2 is struggling and it can and will fail again. Don't fly with that battery other than hovering near ground if you need to check it. If it is still within the warranty period of 6 months, send it to DJI and you might get a replacement.

As to causes, it could be a defect with the battery or it could be something else. Have you used it in either very cold or very hot temperatures? Have you left it sitting for a long time near empty or fully charged? These are just possible causes and there are many factors that can be the cause. If you haven't done it already, you might benefit from some reading on how to properly care for and maintain LiPO batteries. Battery care is a very hot topic even in this forum and there is plenty of information on the topic. But for starters, review your practices and see if any of them might be a factor.
 

spamgnome

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For those types that like this sort of thing, here's the video of how the whole flight went down, including the recover. I edited out the 20 or so minutes where the drone was just hanging out on the corn stalk.
 
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spamgnome

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As to causes, it could be a defect with the battery or it could be something else. Have you used it in either very cold or very hot temperatures? Have you left it sitting for a long time near empty or fully charged? These are just possible causes and there are many factors that can be the cause. If you haven't done it already, you might benefit from some reading on how to properly care for and maintain LiPO batteries. Battery care is a very hot topic even in this forum and there is plenty of information on the topic. But for starters, review your practices and see if any of them might be a factor.
I live in TX, so flying in summer always in the 90s. Is that hot? Yeah, but i believe the max operating temp is 104F. Not ideal, but...
I watch a TON of Youtube videos and read this forum quite a bit and I think I'm pretty savvy on battery maintenance. Again, 2 of my batteries are showing these symptoms, so....dunno. Guess I'll see what DJI think.
 

spamgnome

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So I spent a somewhat unsatisfactory hour on the phone with DJI chat support. We ran through the list he had which consisted of giving them my SNs for the battery, going through a firmware check, etc...he said that if there were no on-screen errors, there was no issue. Bwahahaha!! Here's the best part. He said he was not familiar with AirData!!

This is the 1st time I've had to contact DJI, and any advice on a better route to resolution would be much appreciated.
 
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Meta4

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Here's the best part. He said he was not familiar with AirData!!
That's not surprising at all.
This is the 1st time I've had to contact DJI, and any advice on a better route to resolution would be much appreciated.
Did you synch your flight data (upload to DJI's server)?
That way they can see all the battery data and properly assess the issue.
Without doing that, you're not going to get far.
 

spamgnome

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Did you synch your flight data (upload to DJI's server)?
That way they can see all the battery data and properly assess the issue.
Without doing that, you're not going to get far.
Yes,and they have been in contact requesting more information...we shall see.
 

spamgnome

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UPDATE: DJI has requested that I send the drone in. Interesting. Any guesses as to what they will do? Return it as is? Replace it? Other? I find it interesting that they are more interested in the drone than in the batteries.
 

DanMan32

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Not the first time they've done that, and sometimes they claim something wrong with the drone that was never a problem.
 

spamgnome

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Not the first time they've done that, and sometimes they claim something wrong with the drone that was never a problem.
You mean that they don't want to admit to the real problem and just quietly repair or replace the drone?
 

spamgnome

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UPDATE: Received an invoice from DJI for over $90 for a new battery. No other explanation except that it failed outside of the warranty period. I called in and started a dispute on the findings sighting the fact that even though I didn't become aware of the issue until this incident, the cell in the subject battery (and 1 other!) showed high deviations in voltage way back in March. (I know this from Air Data).
We shall see what happens.

P.S. They completely ignored the part about the drone not warning me of an impending battery failure.
 

DanMan32

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You mean that they don't want to admit to the real problem and just quietly repair or replace the drone?
Worse than that. Say you decide to send in your quad for the battery issue. They may then say you need a new gimbal perhaps because they either saw once "gimbal overload" or saw it in the logs, and arm perhaps because of a blemish that they think is a break. They may see a minor crash in your logs and deny warranty for the issues they found that you didn't have.
I'm not sure if the additional fixes are because they mix up tickets, but they tend not to cooperate to prove what they say is true and for your unit.
At least that's what a few others reported. Could be they weren't accurate. We have had people come here about a malfunction but Sar sees pilot error being the issue or seriously contributing to it.
 

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