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My Mavic Air fell out of the sky and into the ocean.

valgriffiths

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Hey everyone.

I’m pretty gutted. The other day I was flying on a battery of around 70% along the coastline off an island in Croatia and my baby gave me a camera transmission loss msg. It was about 10 meters out and around 300 metres away from me around a corner. It asked me to initiate RTH which I did but nothing happened. I started walking quickly towards it hoping the signal would come back if I were closer but nothing. I manually tried to RTH but still nothing. Nothing I did either increasing altitude or trying to turn it around registered on the screen. No change at all. By this time I’m half running and then, after a couple minutes, disaster! “Disconnected” comes up on a black screen. Noooooooooooooo!!!!! Wtf??! I get to the spot it should be and nothing. Don’t hear it, don’t see it. No one is around to witness. Nothing. My heart is exploding and I know it must have gone down. Anyway. From the gps I kinda knew how far out it was and vaguely where it was and so about 10 minutes later I found it about 16 feet down on the bottom of the ocean. Brought it up and as soon as I got back to shore, took the battery out. It was really tough to get out and then I saw why. The battery was pretty well melted to the drone in one corner. Smelt very burnt. So I’m trying to figure out the chicken or the egg: did the battery ignite and that’s whe the drone took a dive or did the battery ignite because it fell in the water? Can anyone help me there. I rinsed it out with fresh water and frustratingly enough can’t find any isopropyl in the small town I am it so as a last ditch effort and driven by mourning, I dumped it in a bag of rice knowing that would most likely be futile. Took it out today and cleaned it up but with a fresh battery - nada. Didn’t want to try too long with a good battery though. I don’t know what happened. If anyone can shed some light that’d be great. I only got the thing in July and it’s been perfect...until it wasn’t. Managed to get the SD card out right away and that seems fine. All the footage is there save the last video file I was shooting when it went down. It shows the file but there is nothing in it and I don’t cache on my phone. The flight log shows the previous flights, complete with a couple of “interference to signal” messages but the last fateful log shows no messages and just cuts off when the drone went down. I have contacted DJI so waiting to hear from them. Glad I wasn’t flying over anywhere populated but still very bummed. Happy to hear your thoughts as to why this might have happened
Cheers.85A8C21C-18B3-41F4-B204-8AF26E65F0C9.pngCBFB5AC0-00EA-4BBC-A5B2-A21AEED7A552.png
 
You would be doing us all a service if you were to share the flight log on this one. Phantomhelp and/or Airdata (preferably phantomhelp log viewer).

Was it close to shore? Crashed trying to RTH and fell into the water? Perhaps your attempt to initiate RTH from the controller was after it had initiated RTH and you effectively cancelled it, hover until auto land on critical battery?

Good chance the melting occurred after it went in the drink.
 
I do not think the battery melted because of water. Otherwise, why and how did it appear to have smokey scorch marks on the outside and smell smokey? You'd think it would be internally melted only by shorting in salt water. Do the flight logs show any voltage issues with any of the cells at all before loss of signal?
 
You would be doing us all a service if you were to share the flight log on this one. Phantomhelp and/or Airdata (preferably phantomhelp log viewer).

Was it close to shore? Crashed trying to RTH and fell into the water? Perhaps your attempt to initiate RTH from the controller was after it had initiated RTH and you effectively cancelled it, hover until auto land on critical battery?

Good chance the melting occurred after it went in the drink.

Thanks for your reply. I will try and get the log up. It was probably about 15 metres from shore. 54% battery. A couple minutes later it disconnected. No way the battery would have run out in the mean time. I tried to manually fly it up but nothing in terms of a change in figures in altitude showed on the screen. I had an image transmission loss for a few seconds earlier that day and I could still operate the drone and see the altitude/distance change on the phone. It was just super weird. Nothing seemed to respond.

Thanks for the comment re the melting. That's good to know because no-one else seems to have had that issue after their drone has gone for a swim. Possible because mine sounds like it was down for longer?Screen Shot 2018-10-09 at 1.31.45 PM.pngScreen Shot 2018-10-09 at 1.31.45 PM.png
I do not think the battery melted because of water. Otherwise, why and how did it appear to have smokey scorch marks on the outside and smell smokey? You'd think it would be internally melted only by shorting in salt water. Do the flight logs show any voltage issues with any of the cells at all before loss of signal?

It was melted internally and not externally. I have included the logs in the thread. There was no change to the batteries voltage during the flight before it went down. The battery was at 53% at the end of the log. It is all super weird. It was in the middle of the ocean with nothing around it and definitely didn’t hit anything.
 

Attachments

  • DJIFlightRecord_2018-10-05_[10-59-49]log.zip
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I wouldn't think the battery could get hot enough to scorch the outside while it was immersed in water.
1539101049698.png
But I am no thermal expert.
 
That sure looks like a thermal runaway event in one of the cells. If anything, the dunk in the water kept the second cell from lighting off.

Do the flight logs show anything about battery temperatures, by any chance?
 
@sat104 might be able to figure this out
 
You might be able to recover the last video. Normally you just power the AC back up and it will close and finalize the video but obviously you can't do that.
But with a utility someone developed, if the actual video is there, it can rebuild the file.

Here's the link: Repairing Corrupt DJI Video Files
There's a YouTube video on how to use it.
 
That sure looks like a thermal runaway event in one of the cells. If anything, the dunk in the water kept the second cell from lighting off.

Do the flight logs show anything about battery temperatures, by any chance?

Hi. Thanks for commenting. No, not that I can see anywhere. But this is my first foray into even looking at my flight logs.
 
You might be able to recover the last video. Normally you just power the AC back up and it will close and finalize the video but obviously you can't do that.
But with a utility someone developed, if the actual video is there, it can rebuild the file.

Here's the link: Repairing Corrupt DJI Video Files
There's a YouTube video on how to use it.

That is super useful. Thanks - I'll take a peak at that. Yes, I thought the file was empty but upon second glance, there is 300+MB of data in there - it just won't open, as you say. Very cool. Thank you! I'll let you know how that goes.
Cheers!
 
That is super useful. Thanks - I'll take a peak at that. Yes, I thought the file was empty but upon second glance, there is 300+MB of data in there - it just won't open, as you say. Very cool. Thank you! I'll let you know how that goes.
Cheers!

You can also usually repair it by putting it in a DJI aircraft and powering it up.
 
That is super useful. Thanks - I'll take a peak at that. Yes, I thought the file was empty but upon second glance, there is 300+MB of data in there - it just won't open, as you say. Very cool. Thank you! I'll let you know how that goes.
Cheers!

I bet it was smoking as it fell, and the battery shut down before the last flight data was written to the card. Too bad there were no witnesses.

Was it an original battery or purchased from someone other than DJI? Knock-offs are rampant and pretty indistinguishable from OEM. Any type other than OEM will void any warranty, plus puts an airship in danger along with those below it (fires, impacts, etc.)

Sorry this happened to yours, Val.
 
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That is super useful. Thanks - I'll take a peak at that. Yes, I thought the file was empty but upon second glance, there is 300+MB of data in there - it just won't open, as you say. Very cool. Thank you! I'll let you know how that goes.
Cheers!

Did you sort out why the battery melted? I had a similar problem...lost connection, the drone fell in sea water for 1m. A few minutes later as i went to wash it, i noticed that the battery had melted into the plastic.

Did DJy reimburse you?
 
Did you sort out why the battery melted? I had a similar problem...lost connection, the drone fell in sea water for 1m. A few minutes later as i went to wash it, i noticed that the battery had melted into the plastic.

Did DJy reimburse you?
Note that the last post before our question was 2 years ago.
 
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