I was flying my Mini 4 pro over some Aspens on a mountain side, about 1-1.5mi from me and mid-flight the controller said, "critical battery. forced landing". I had no control, the drone was descending. The controller showed a video of what was happening, and the drone was headed straight down for the canopy of a tree, then it went blank!

  

I used the 'find my drone' feature on the controller and I was surprised it worked without being connected to the internet. It showed me exactly where the drone went down. I followed the line shown on the controller and after an hour or so of bushwhacking my way through the forest I found the drone! It had fallen about out of a tree about 40ft above me. The only damage it sustained was a crack in one of the propeller arms.

I was impressed with the find my drone option, accurate within 10ft. And this little drone can survive a 40ft fall apparently.

Video before the crash https://www.instagram.com/reel/Cydk3k9LjBF/?igshid=MzRlODBiNWFlZA==

Oh wow interesting. Hope you can share the video and flight log!  Hope you can get your drone back up if all you need to do is replace the props.

Also the drone flys perfectly fine with the cracked arm. The crack is about 1 inch. I put a dab of super glue and shes good to go

Did the drone's battery suddenly drop to critical battery levels or did it gradually drop to those levels?

Sean-bumble-bee Posted at 10-18 12:16
Did the drone's battery suddenly drop to critical battery levels or did it gradually drop to those levels?

The battery was about 40% when I sent it out. Of course it’s always good to start a flight with a full battery. Usually the drone signals when the battery is low and it retunes home. That didn’t happen this time, just bam critical batter I’m going down!

Monkieboy00 Posted at 10-18 12:26
The battery was about 40% when I sent it out. Of course it’s always good to start a flight with a full battery. Usually the drone signals when the battery is low and it retunes home. That didn’t happen this time, just bam critical batter I’m going down!

Does that translate to, you started the flight at 40% battery and flew it 1 to 1.5 miles away without occasionally glancing at the battery charge ?
If so, do you think that was wise ?

It might be informative to go to
https://www.phantomhelp.com/LogViewer/Upload/
read the instructions there, retrieve the flight log, up load it to that site and then either replay the flight and watch the battery level decline or post the resulting URL here.

Thanks for sharing, beautiful short video of the aspen tops!

Hello, there. We're sorry to hear about the incident that happened with your recent flight. Please send your aircraft for service via this link: repair.dji.com Rest assured that data analysis will be provided to investigate this incident and possible warranty coverage, however, please know that this will depend on the outcome of the investigation. Thank you for your cooperation and understanding.

[ Last edited by Monkieboy00 In 2023-10-18 15:48 Editor ]\n\n[ Last edited by Monkieboy00 In 2023-10-18 15:47 Editor ]\n\nHere is a screen record of the flight log. You can see the batter go from 20% to 7% in a couple of seconds


Well i tried to upload a video but this website doesn't do what it says its doing. Just as bad as the drone lol

Heres a youtube link to the flight log.

https://youtu.be/vOKPwknqAyc?feature=shared

Other than possibly obvious faulty battery/drone, was it really windy at the height you were at, so the drone struggled a ton, or very cold that could mess with the battery?

But yeah, as others mentioned, the flight logs uploaded to this site https://www.phantomhelp.com/LogViewer/Upload/ will give you all the tech parameters as to what the drone was doing at the time.  Not just the path as you uploaded above in the video, but voltage, motor speed etc.

The "DJIFlightRecord_2023-10-15_[16-32-19].txt"  flight log, as suggested by A1C, would be better but the sudden drop in battery charge from 20% to 7% youtube time 2:41, log time 5:22 to 5:24 is unusual.
How old was the charge?
The battery flight time remaining also bounces around a fair bit.
The take off was quite high, around 8,500ft I think, and you you sent the drone up to around 10, 042ft which probably didn't help the endurance.
Where did you get the "about 1-1.5mi from me" from? 1130m is around 0.7 miles.

Monkieboy00 Posted at 10-18 12:26
The battery was about 40% when I sent it out. Of course it’s always good to start a flight with a full battery. Usually the drone signals when the battery is low and it retunes home. That didn’t happen this time, just bam critical batter I’m going down!

Thats the problem, starting with a partly charged battery will inevitably show an incorrect charge amount, the only caveat there is if the flight was made shortly after another flight that used up the 1st part of the battery, I'm talking about prob within a few hrs, although, that could be pushing it, its perhaps down to minutes prior.

Sean-bumble-bee Posted at 10-18 17:47
The "DJIFlightRecord_2023-10-15_[16-32-19].txt"  flight log, as suggested by A1C, would be better but the sudden drop in battery charge from 20% to 7% youtube time 2:41, log time 5:22 to 5:24 is unusual.
How old was the charge?
The battery flight time remaining also bounces around a fair bit.

As youve said, the altitude will no doubt have played a part in this too, this will have supped the battery faster than if it was down at sea level, so add that to starting a flight with 40% battery, its a recipe for disaster and ultimately taking it home in a carrier bag

Monkieboy00,   I had a similar accident very recently, well similar in the way,  battery was depleted.  I found this forum and DJI support excellent.  Theirs also people on the forum that will look at your logs via PM etc.

Monkieboy00 Posted at 10-18 12:26
The battery was about 40% when I sent it out. Of course it’s always good to start a flight with a full battery. Usually the drone signals when the battery is low and it retunes home. That didn’t happen this time, just bam critical batter I’m going down!

I also suggest you post a photo of the 1" crack in the arm.

Monkieboy00 Posted at 10-18 15:48
Heres a youtube link to the flight log.

https://youtu.be/vOKPwknqAyc?feature=shared

Hi,

Normally when the battery icon amber section gets bigger and the green section shrinks, when the green section dissapears a RTH countdown is seen.....

Not in this log!  curious now to see the flightlog.

cheers
JJB

I think the moral of the story is…don’t go flying without 100% battery charge

Steph Jant Posted at 10-19 03:13
I think the moral of the story is…don’t go flying without 100% battery charge

Not necessarily, obviously you should not attempt to go far on a significantly depleted battery but it is my experience that if the charge on the battery was old the behaviour of the battery can not be relied upon.

Cold air could be the cause for the voltage drop under higher current draw the moment the drone was getting sped up. This is a common problem, cold lithium batteries cannot deliver high currents the way they can if they are warm. If you try, the voltage is dropping significantly. This leads to a sudden drop in the capacity number.

Hi guys, I am unable to locate the flight log. I followed the instructions but I don't have all of the options shown. Maybe things have changed with the 4pro. I don't have the steps under audio that show DJI RC
I beleive my flight logs are sync'd because it shows a little cloud icon over each log.
If someone is familiar with the 4pro controller (with the screen) please post the steps

Monkieboy00 Posted at 10-19 07:14
Hi guys, I am unable to locate the flight log. I followed the instructions but I don't have all of the options shown. Maybe things have changed with the 4pro. I don't have the steps under audio that show DJI RC
I beleive my flight logs are sync'd because it shows a little cloud icon over each log.
If someone is familiar with the 4pro controller (with the screen) please post the steps

Hi,

My RC4pro logs are here....

\\DJI RC 2\Internal shared storage\Android\data\dji.go.v5\files\FlightRecord

cheers
JJB

JJB* Posted at 10-19 07:21
Hi,

My RC4pro logs are here....

Oh connected to a PC. The instructions showed this was all on a controller.

Monkieboy00 Posted at 10-19 07:27
Oh connected to a PC. The instructions showed this was all on a controller.

log is on the RC, so connect to a PC ; use file explorer to copy paste to your PC
You can also browse on the RC....and via bluetooth transfer the file....or via wifi xfer   (PC is so much easier...)

Thanks everyone for your feedback, clearly i'm new to the drone world lol. First time having one,

here is the flight log https://www.phantomhelp.com/LogViewer/5H59GAEPFS0TF0ZG0PN7/

Here are photos of the damage. The drone flys perfectly fine

Monkieboy00 Posted at 10-19 07:35
Thanks everyone for your feedback, clearly i'm new to the drone world lol. First time having one,

here is the flight log https://www.phantomhelp.com/LogViewer/5H59GAEPFS0TF0ZG0PN7/

Hi,

Had a look at your flightlog.

I understand now that there was no countdown for a RTH.
The battery in % went from 20 to 7% level, as 7% is below the critical value your Mini4Pro into AutoLanding.
The cell voltages of the 2 cell  did not drop at all, so 20 should be 19 ect   and not 7% in 0.1 second.
Starting a flight with 39% is not the reason for this, question is ofcourse if it i wise to fly 901 meter / 2957 feet away from HP with just 20% battery.

DJI should look into this error.

cheers
JJB    [ Charts by FRAP ; the 'best' software for data and visual flightlog analysis (www.jjbfrap.eu) ]

JJB* Posted at 10-19 09:32
Hi,

Had a look at your flightlog.

Thank you for that info!

Is there a way to have DJI look at this flight log without me sending the whole drone in?

Monkieboy00 Posted at 10-19 09:35
Thank you for that info!

Is there a way to have DJI look at this flight log without me sending the whole drone in?

I would contact dji support, they don't need the drone to look at logs, I found them excellent, they will send logs for analysis and come back to you accordingly if my experience is anything to go by.  Thank you

I am not an expert but a sudden drop from 20% to 7% must have a source of error

Monkieboy00 Posted at 10-19 09:35
Thank you for that info!

Is there a way to have DJI look at this flight log without me sending the whole drone in?

Send one of the mods a pm asking if the log could be looked at.
If you have synced then they actually do have the logs already, whether or not the relevant section of DJI can access them is another matter.
Were the any .DAT logs in the MCDatFlightRecords folder?

Incidentally with the damage shown in your photos I think YOU SHOULD send the drone and drone in for repair/replacement.
If the battery readings stem from a fault in the drone or battery this should be a warranty matter and FOC.

I filed a repair ticket and am sending the drone in for investigation. I’ll report back with the results when I get them.

Beside the large damage in the actual arm, this rotor is no longer aligned with the other opposite side, making the drone working twice as hard to hover in one place...

Arm and rotor definitely need to be replaced...

Dirty Bird Posted at 10-19 15:51
Question to the OP:  How long was it between the launch of this flight @ 40% battery & when the drone was flown previously (with this same battery)?   If it was very recent, same day only a brief time after previously landing, no big deal.  If it was hours or days previously then this explains the seemingly "sudden drop".

Herein lies the risk in flying a partially depleted battery.  The flight computer calculates battery level based off battery voltage.  This is a very imprecise reading as voltage does not accurately reflect how many amps remains in the battery, & voltage can quickly change when flying a partially depleted pack.  After a long flight, the voltage has dropped but, power down & allow the battery to rest, voltage will recover & increase.  Power up after the battery has cooled & recovered, the initial voltage is now much higher than when you previously landed the pack.  The drone, basing it's battery level off voltage, incorrectly estimates more power than actually exists.   Placed under load, the battery voltage quickly sags, as does the estimated battery level remaining.

Hi,

What you describe make sense

But this is seen that at start the batt voltage is a x volts, and quickly after takeoff voltage drops rapidly, from that point the decrease in voltages are kind of linear.
Not in this log.

Start a flight with non full battery is no problem, as the previous use was recently.
Do not use a non full battery wich has not been used for few days is my policy.

cheers
JJB

JJB* Posted at 10-20 00:01
Hi,

What you describe make sense

If you're familiar with fpv, when the battery pack cells drop to 3.5 volts, we land the drone.  Within a few minutes if you measure the voltage it goes up to 3.8 or so even though the battery is essentially drained now.

If you use that battery again you will have a short flight.  This might have happened to you as well, and the cold temps may have made things worse.

Monkieboy00 Posted at 10-18 15:48
Heres a youtube link to the flight log.

https://youtu.be/vOKPwknqAyc?feature=shared

flying over 400m, is that even legal?

him7403 Posted at 10-20 13:47
flying over 400m, is that even legal?

Definitely have gone above 400ft. But it depends on where you’re measuring from- take off or the current ground below the drone. Flying up the side of a mountain you can ascend 3000ft from the home location and still maintain 400ft from the ground.

I am interested in buying a mini 4 so I am researching real users comments. Because of that I noticed this battery issue and feel I can offer helpful comment.
Of 5 Mavic pro batteries of the same age (2017) I was nearly caught out with a sudden battery failure on one battery. I usually land with 30% left but on this occasion, I was 500metres out when the % left dropped to 10 then 2% in a few seconds and auto landing was triggered.
OK, the drone dropped onto soft sand and was undamaged. I decided to test all batteries for endurance by flying in a POI setting at a low altitude and slow speed until 20%.
The result was clear, 4 batteries were 2 minutes below the as new value at 18 minutes and the suspect battery failed and self landed at 11 minutes.
The point being, do regular battery endurance tests to see if you have a problem brewing.
My battery habit is to fly only with a freshly charged battery down to 30% and no lower. Other folk have their own opinions about battery usage.

Hello guys, 1st post. Glad to hear your drone still flies after eating it!

I just bought my Mini 4 Pro 4 days ago and already it is throwing the "Downward Vision Sensor" error. Cleaned cameras, updated firmware through DJI Assistant 2, reboot, and all the other online tips and tricks. Everything has been calibrated. I don't have a error code number or screen shot. RC2 showing the error in red, pretty straight forward.

1st flight was flawless, 2nd flight it raised to 1.2 meters and threw code. I've already submitted a DJI case#. Bummer for sure. We shall see, and yes I have DJI Refresh, but 4 days old, really? Yes, the retailer is aware of the problem as well and I can always return it. Waiting to see where DJI stands on this. Time is money.

Thanks for your response, however, there is no option to "calibrate" within DJI Assistant 2 for the Mini 4 Pro that I could see. Please confirm with the other DJI Guru's that this is a viable option. Thanks.