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Lost Mavic 2 Pro - Battery failure
131 9 2021-11-28
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lecoqadoodledrone
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After nearly 150 flights with my Mavic 2 Pro and 400+ in total with my previous drones (P3P & P4P+), I "finally" joined the club of those who lost a drone ...

Nothing fancy and daring, just a classical flight that started well but then started getting a warning at the 56 seconds, with the battery level going from 91% to 0% and "informing" me that the controls of the drone would be from now limited and that immediate landing procedure had started ...

1m34s it was in the water ...

Between the first message (that was beeping up every second until the end), I could only control the rotation of the drone, but in no way go forward, left or right and of course not backwards ...

So, it didn't fall or drop from the sky, but was a "controlled" descent but with very limited possible maneuvers which really frustrated me since from 90 meters to ground or water level, I technically had the time to go from the middle of the canal and land on one of the banks of the canal I was flying above.

All my batteries have been serviced every 20 flights and no pre-warning signs or messages prior to this incident - The battery itself had only 43 charge cycles ...

Here is the airdata link in order to try to understand what happened ...


Clearly possible to see that it is the battery that failed but at the same time, I don't get how such a product can fail when I never had an issue with my P3P and P4P+ (still have the last one that works perfectly)

Also, planning to send some feedback to DJI - Not that I expect anything from then, out of warranty and no DJI fresh, but they should be informed that such an incident occurred with a person who has always taken good care of his equipment ...

Thanks in advance for anyone who will give some feedback on the info provided in the airdata link ...

Matt

2021-11-28
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Labroides
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Your recorded flight data shows a real problem with that battery.
The first question that comes to mind is:
How long before teh flight was the battery fully charged?
It was showing a nominal 95% at launch, but when you stopped climbing and hovered from 22.3 seconds, the cell voltages were all showing 3.7V, which is too low after only 22 seconds flight.
You climbed again from 37 seconds and this put all battery cells into critical low voltage level (< 3.2 volts) at 45.2 seconds, under heavy load with left and right sticks pushed full forwards.
Shortly after, many Not Enough Force warnings started to show.

All cells recovered to 3.3-3.5 V at 57.7 seconds, even though you still had you still had both sticks full forward.
This would be related to the warning that showed up at around the same time:
Battery power limited automatically reduces device mobility to ensure flight safety.

You continued to fly the drone further away until 63 seconds when it reached 800 ft from home.
1.5 seconds later you pulled the left stick hard down, initiating landing.
You never tried to fly back until 3 seconds before the drone submerged.
After the warnings showed up, you used up most of the battery power trying to hold the drone up.
2021-11-28
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DAFlys
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Thats a common fault with the M2P,  something that worries me.
2021-11-28
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JJB*
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Hi,

Had a look at your flight too.

In addition and other view to post#2 ; at 55s in flight battery cell #2 reached a verly low value of 2.647 volt. Forcelanding is initiated because of this low voltage value, software tries to land craft before it droppes out of the sky to due to extreme low battery power fail.

cheers
JJB
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2021-11-28
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lecoqadoodledrone
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Labroides Posted at 11-28 00:45
Your recorded flight data shows a real problem with that battery.
The first question that comes to mind is:
How long before teh flight was the battery fully charged?

Thanks for getting back to me …

The battery was fully charged in the morning of the flight.

The reason why the battery was at 95% at takeoff, is because the temperature being 11°C, I turned the drone on a couple of minutes before connecting the remote for a slight warm up.

The reason why I stopped and hovered at 22,3 seconds, it that having taking off, I aligned myself to start filming …

During those 37 seconds of climb, there was no reason for me to suspect there was a voltage problem until that message.

I may indeed have continued a little the flight trying to assess exactly what was happening during some seconds.

But what really bugged me was the 0% indication for my battery and the constant beeping saying that a forced landing was initiated. Also, I recall not having any more indication of the altitude.

You do say that I never tried to come back (not sure what was the best solution at that time), but I decided with the information I had at that time, that trying to fly back was not the best solution and try to accompany down the drone asap and try to find a place to land … Did that mainly because I had absolutely no idea of how much power was really left when I have on my screen 0% and flying back 200+ meters meant I needed a certain amount of power.

I order to check where I could land, I tried to play with the pitch of the gimbal to look downwards, which didn’t work stopping me from having a clear view of my surroundings. Only solution at that point was to continue going down in order to get a reference point on which I could make a decision on where to go.

Unfortunately by the time I understood where the drone was and at what altitude it really was, I was too low and tried to head to the bank of the canal.

I see in the Airdata values, that even though I throttled up, since the drone was in forced landing mode, it had no effet on the altitude. This I remember clearly with the live feed of the screen that it didn’t go up at all.

Then the last turn, is more of a desperate last chance action …

Not trying to find excuses here, just plainly explaining the situation …

For sure, during a day flight, getting your bearings with every second pop up message and beeping, could have been more easier.
2021-11-28
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lecoqadoodledrone
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JJB* Posted at 11-28 02:41
Hi,

Had a look at your flight too.

Thanks also for getting back to me ...

Never had this situation before and that is the reason (force landing) why I didn't try to head back and all what I just explained in the message just above ...

2021-11-28
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DJI Stephen
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Hello there Matt. I am sorry to read and to know what happened to your DJI Mavic 2 Pro. Since this unfortunate incident happened to your DJI Drone. I would recommend for you to contact our DJI Support Team at https://www.dji.com/support?site=brandsite&from=nav for further assistance. We have a team that will do there best to help you and give out the best resolution for the said issue. Again, I am sorry for the trouble and thank you for reaching out.
2021-11-28
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GaryDoug
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This will not help much. But I have troubleshot many defective L-ION battery packs, being an EE and can't help myself ;-) I have yet to find even one which failed because of a cell failure. The failure was always with the electronics falsely indicating cell failures and shutting off the whole battery. I think they are now designed extremely conservatively to avoid dangerous situations like this one: https://www.flyingmag.com/news-u ... ium-battery-danger/

Just yesterday I received an eBay shipment of a Lithiun Ion battery pack. The required FAA label was loose inside the box and not affixed to the outside. This package, obviously to me, came via air freight.

2021-11-28
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Labroides
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lecoqadoodledrone Posted at 11-28 18:38
Thanks for getting back to me …

The battery was fully charged in the morning of the flight.

During those 37 seconds of climb, there was no reason for me to suspect there was a voltage problem until that message.

If you are flying with DJI Go 4, there's a handy option to help you keep an eye on the battery voltage so that you don't have a nasty surprise when it's too late to do anything about it.
In the app settings, you can have the battery cell voltage show as well as the % indicator.

If you fly a drone that uses DJI Fly, that option is probably missing, like so many other useful things.

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2021-11-28
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lecoqadoodledrone
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Labroides Posted at 11-28 22:26
During those 37 seconds of climb, there was no reason for me to suspect there was a voltage problem until that message.

If you are flying with DJI Go 4, there's a handy option to help you keep an eye on the battery voltage so that you don't have a nasty surprise when it's too late to do anything about it.

Next time ;-)
2021-11-29
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