Hi,

I had an issue with my Mavic Air the other day which saw me lose the Mavic Air completly. After take off there was hardly any control over the device. Satellites were locked and flight should have been fine, there was a little wind but nothing much, but it was almost completly unresponsive before going down into the lake. I'd tried to switch into Sport mode to gain some traction to move it somewhere that I could land it but it didnt change anything.

I saw from the logs that there were lots of ESC warnings:

Warning

[url=]Not Enough Force/ESC Error (repeated 50 times)[/url]

I posted the full log here:

https://app.airdata.com/share/prqsGw

Not a great day as all the previous footage taken that day was also lost when the drone went down.

Its really strange as there was a low voltage warning at one point even though the battery was still at 42%

Tip	[url=]Critically Low Voltage Warning Aircraft Landing[/url]

Very sad.

Sorry to hear you lost your bird.

Ouch - sorry to read that

That sucks  big time. Sorry...
But when you get your next bird, try to: once the AC is powered up, GPS locked, Compasses checked, IMU checked (all green status),
Then lift off maybe 10/15 feet, and check every control input. A small forward, a small back, a small left, a small right movement.
If everything is good, and the AC feels good and responds to commanded inputs, then it's time to roll the dice and go for it.

Flycaster Posted at 7-27 11:25
That sucks  big time. Sorry...
But when you get your next bird, try to: once the AC is powered up, GPS locked, Compasses checked, IMU checked (all green status),
Then lift off maybe 10/15 feet, and check every control input. A small forward, a small back, a small left, a small right movement.

Good advice mate

Flycaster Posted at 7-27 11:25
That sucks  big time. Sorry...
But when you get your next bird, try to: once the AC is powered up, GPS locked, Compasses checked, IMU checked (all green status),
Then lift off maybe 10/15 feet, and check every control input. A small forward, a small back, a small left, a small right movement.

Yes, that’s a good idea if you have the ability to do that. Mine as soon as it went up in the air was off on its own course. The flight lasted less than 7 seconds...not really enough time to do those checks ( which I would normally do)

Hello there kn0xster. I am sorry to read and to know what happened to your DJI Mavic Air. Since this unfortunate incident happened and you have lost the said 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. If the said drone is still under the warranty period and it is evaluated as a non-pilot error, the warranty service will be provided. Again, I am sorry for your loss and thank you for your understanding.

Its really strange as there was a low voltage warning at one point even though the battery was still at 42%
It's not strange at all.
It's an indication that you launched with a battery that had been discharged for some time.
What matters is the voltage of the battery, not the % indicated.
The % indication is completely unreliable unless you launch with a fully charged battery.
Airdata shows that the battery cells dropped to below the critical low voltage level (3.3V) in the first 4 seconds of the flight.

If you want any more details, in Airdata you need to tick the box that says Share so others can see the actual data rather than just the Airdata summary.

ok, thanks. I changed the sharing:

https://app.airdata.com/share/jwEgih

kn0xster Posted at 7-28 04:12
ok, thanks. I changed the sharing:

https://app.airdata.com/share/jwEgih

You can see what that flight data looks like here:  https://www.phantomhelp.com/logviewer/8A3854BT3MXX4TWKPJKC/
It shows how low the battery really was, note the voltage per cell dropped to 3.3 volts almost immediately under the load of launching.
It tried to land due to the battery level being too low but being pushed to climb  caused the battery voltage to collapse below critically low level (3.3V per cell).

From 0:13, you pushed the right joystick hard forward until 0:18.5 which took the drone from 7 metres to 24 metres from the home point and took it toward the lake.
With the battery level so low, the drone was unable to stay in the air and it came down.

A J Posted at 7-27 12:06
Good advice mate

Really good advice, except it's completely irrelevant to this incident.

Labroides Posted at 7-28 05:38
Really good advice, except it's completely irrelevant to this incident.

So it is but yeah, as you say, really good advice.

for me it's a faulty battery (BMS or cell / both)
voltage drops in 4 sec down to 3,2V?, yet BMS still lies about % also warnings are strange + late
get a warranty claim

So DJI sent me an offer to replace the main Mavic Air unit (I am assuming without battery) with a 10% discount.



508 EUR.... I can buy a new unit complete with RC, props, battery and case for an extra 56 EUR. Needless to say that I don't think I'll be taking them up on the offer especially as they are only looking to replace like with like for the last generation unit.

I will be looking for something a little more reliable when spending that kind of money in future.

KREMi Posted at 8-1 10:51
for me it's a faulty battery (BMS or cell / both)
voltage drops in 4 sec down to 3,2V?, yet BMS still lies about %  also warnings are strange + late
get a warranty claim

If it was a battery issue then why I didn't I get a warning? I would have landed immediately.

kn0xster Posted at 8-5 05:37
If it was a battery issue then why I didn't I get a warning? I would have landed immediately.

did You even read what did I write...?
if something is not working as it should (aka FAULTY) how can it give You proper warning??
You can clearly see, that % of overall battery stays >40%, yet single cells voltage is...
and battery in good condition should not discharge from around half full to almost dead in 4sec

if You accept that this was somehow Your fault - ok (maybe we don't know some extra details of this story like battery was bad earlier, mayeby not genuine, some mods, etc)
but any other case - IMO this should be taken care under warranty - bird should spam You with warnings from 2nd second of flight with criticall battery, etc

(and I agree, that You did not follow any decent starting procedure (gps-fix, sensor values check, basic movement check) as then it would also help diagnose, something is not right - those 15-20sec checks are really worth it)

KREMi Posted at 8-5 10:13
did You even read what did I write...?
if something is not working as it should (aka FAULTY) how can it give You proper warning??
You can clearly see, that % of overall battery stays >40%, yet single cells voltage is...

KREMi, yes i did read what you wrote and I found it very useful. My answer was more out of frustration than of not reading what you wrote. There were no mods to the battery and the battery is the same one that was used for the previous flight earlier that day. It showed no signs of any issue during that flight.

I’d love it to be covered under warranty but the device is out of warranty for a while now. Unfortunately as this is the case I dont think DJI really cares about investigating this further especially as they’ve moved on to the Mavic Air 2 now.

kn0xster Posted at 8-5 14:47
KREMi, yes i did read what you wrote and I found it very useful. My answer was more out of frustration than of not reading what you wrote. There were no mods to the battery and the battery is the same one that was used for the previous flight earlier that day. It showed no signs of any issue during that flight.

I’d love it to be covered under warranty but the device is out of warranty for a while now. Unfortunately as this is the case I dont think DJI really cares about investigating this further especially as they’ve moved on to the Mavic Air 2 now.

This is just messed up.  I am sure if you had a warning you would've landed asap.  What is going on with these batteries?  So sorry you lost your bird.  To make it worthwhile, they should give you at least 50% off..  Just like my battery issues.  We will see what happens when they get back with me.

The chart says takeoff battery was at 46%. Without seeing the full logs i'd say a cell died mid flight. This would mean the remaining cells could not drive the motors fast enough hence the ESC errors.

Lesson to learn, always fly with a freshly charged (that day or day before) battery.

But having said that, a sad loss indeed.

Ken Storm Posted at 8-6 03:30
The chart says takeoff battery was at 46%. Without seeing the full logs i'd say a cell died mid flight. This would mean the remaining cells could not drive the motors fast enough hence the ESC errors.

Lesson to learn, always fly with a freshly charged (that day or day before) battery.

Ken, Agree completely, but part of the reason for getting the Mavic Air was to be able to sling it in a backpack for a days hike without having to take everything with me. Thats why I didn't use a fresh battery.  I guess I made the mistake of assuming that having at least 40% would be good for a quick 5 minute flight.

I've done the exact same thing, fortunately for me, I was only a few meters up over long grass, so the quite sudden drop did not cause any damage.
I now regularly check bat voltage after a flight using FRAP. Any battery that looks like a cell is drifting to far out compared to the rest gets cycled.
That is drained to <10% keeping an eye on the individual cells then fully recharged as balancing of the cells only occurs at the end of the charge cycle.

Well DJI offered me a 25% discount in the end to purchase a new Mavic Air. So I‘ll take that for now and hope I dort have any new issues with it. Ill have to check the other batteries though.  I still don't think that DJI are actually going to look into the issue and see what actually happened.

I subscribed to the AirData service to see the battery health for a while and looking at the graphs should I be worried about the other battery?

This is the one that was in the drone when it was lost. You can see that there were quite a few deviations before the last disaster flight:



This is my second battery, which looks to me like its going the same way as battery #1:



The battery #3 which looks ok for now:



Am I reading these right? Should I cycle battery #2 to try and fix it before something happens or should I just retire this battery?