After buying a new battery on Amazon (which according to seller was 100% Compatible with my DJI Mavic Pro 2)
I went out to make a little flight - also to see if the flight time was possibly somehow improved with this new battery!

- All went smooth, i took off from the park area and moved 150mt away when after approx. 1Min i lost the signal!
(Battery was still at 98% - i was flying on 120mt altitude and there was any kind of possible signal interference).

- All i know is that the drone never came back but i've seen it going down in the area where it lost the signal!
(which is strange since i don't remember ever changing those setings - it was supposed to just come back)
Here's the link to the flight record: https://www.phantomhelp.com/LogViewer/38RS8WX56EJ97LIVSB6N/

(According to that log, the battery voltage dropped to critical levels and is something that was not suppose to happen!
Also i compared it with the flight records when i Was using original mavic batteries and they didn't have that issue..)

Can someone give a look to that log to help me find
any potential information to find drone?



The last coordinates according to find my drone app: 41,07463° N, 14,31300° E
I did carefully check that area and the drone wasn't there, but i don't know how accurate they are..
Let's suppose that it did not land on that exact spot and it was not stolen by a person walking by....

- Is there a way to know it latest position altitude?
- Is there any chance the drone decided to land on top of house roof?
- Is there any device that could help me to spot the drone even if it's off?
- Anyone in here knows of similar experiences with not original batteries?

After i lost the signal, it never came back
even after i went to the drone location.

It's been 2 Days Now, I'm still optimistic!
Looking for your help, thank you.

Is there a chance that it landed in the trees right beside the landing spot?

It sure looks like a battery issue. It was fine at the beginning when you were just hovering but it didn't seem up to the task once you started to make it work.  

It is sitting in a tree branch and wondering when you are coming back to retrieve it.  Sounds like a bad day.  

It's important to always fry with a freshly charged battery.
If you use a battery that has self-discharged the % indicator reading will be false.
In your case the battery % indicator showed 54% at the start, but by 35 seconds the cell voltages are 3.4 volts, nearing critical low voltage levels as you climbed.
You pushed the drone hard, either climbing or flying forward at full stick for the whole, short flight.
This quickly drained the weak battery.
At 1:17.9 when the data end, two of the battery cells were already at critical low voltage level.
It's likely that the battery gave up and the drone came down.

When the data stopped, the drone's location was above 41.07421  14.31302.
But it was 130 metres up and flying forward at 12.5 m/sec.
From that height and speed, the drone is likely to have crashed approx 100-120 metres further east from that point.

That's what you get for using cheap knockoff batteries, an expensive lesson for you. Let's just hope no one got hurt.

Do not use 3rd party batteries unless you want to lose your drone.

CloudVisual Posted at 3-17 14:09
That's what you get for using cheap knockoff batteries, an expensive lesson for you. Let's just hope no one got hurt.

Do not use 3rd party batteries unless you want to lose your drone.

The problem was that the battery had been lying around discharging.
That can happen with any battery, whether original DJI or not.

CloudVisual Posted at 3-17 14:09
That's what you get for using cheap knockoff batteries, an expensive lesson for you. Let's just hope no one got hurt.

Do not use 3rd party batteries unless you want to lose your drone.

Things can happen with any battery, I've been flying 3 years with 3 3rd party batteries which have all the tech of the original DJI batteries and never had any issues.

Hi, Roman Aitch. Thank you for reaching out and we're deeply sorry for the incident that happened. In this kind of situation, please consider creating a flyaway case for a proper analysis. You may submit a flyaway case request through this link: {https://repair.dji.com/repair/index}. If you need assistance with creating a ticket, you may contact DJI support at https://www.dji.com/support. In addition, please note that free data analysis may not be supported if the unit is already out of warranty. If the unit is out of warranty and a data analysis has to be applied, we can provide a paid data analysis, which may cause $65, and the data analysis result will not affect the service solution. Your kind understanding is appreciated and thank you for your continued support.

Hi,

Had a look ayt your flightlog too.

"Battery was still 98%", not shown in the log looking at the actual values.
At start 54%, end of flight 48%, good idea always to check cell values direct after take-off.
I always fly with screen recording active, good for extra analysis/comparison what you see on the screen and in the log.

BUT cell values not that bad, see my charts of your data.

3.3 volts is a low value in flight, but drone does not drop ouf of the sky at 3.3 or 3.2 volts.
If one cell or more cells < 3 volts than drone enters an autolanding.

At disconnect cell values : CellVolt | #1 3.294 | #2 3.313 | #3 3.316 | #4 3.267 |
In the log no warnings or messages about reaching or at critical battery level.

So what happend....after loosing contact your Mavic2 into FailSafe RTH.
Don`t see any reason why it should not go into a RTH, battery wise not a problem.

If on the way back home the cell values drop to a real low value ; into Autolanding.
As it did not came back to you....so somewhere between last known position and HomePoint it autolanded.

cheers
JJB   [ Charts by FRAP ; the 'best' software for flightlog analysis ]

Prairie Chicken Posted at 3-17 12:49
Is there a chance that it landed in the trees right beside the landing spot?

It sure looks like a battery issue. It was fine at the beginning when you were just hovering but it didn't seem up to the task once you started to make it work.

I did check the trees, but couldn't find it.
Do you know if by any chance it can auto-land on roofs?

JJB* Posted at 3-18 02:27
Hi,

Had a look ayt your flightlog too.

Thanks alot for you detailed analysis, it is really helpfull!
@Labroides and you both pointed out that the battery was not at 98%

That's true, my bad - the controller and app were both reporting 54%.
However i did not mention something important, which i'll talk about:
that was the second flight with that battery!

- The very first flight with the amazon battery was few hours earlier in different location
and it lost connection same way and landed in same location where it did disconnect!
Took me one hour to find it - was in a bush around 5mt from where it lost signal
(but in that case the controller did connect back to drone after i reboot)

Attached below a screenshot of the last seconds of the first flight before disconnecting..
(It took me around 1 Hour to find it, so when i found it Battery was half discharged)

After i found it, it was in great shape which means it didn't fall but it only landed.
The battery was at 54% at that point and i didn't connect the incident to the new battery!
I thought it was just a signal issue or something like that, so i just moved to a different location!

So before the incident, i made few more flights with original mavic batteries without problems
and then when i put back the new battery, It did happened again and i didn't find it yet!

Roman Aitch Posted at 3-18 07:36
I did check the trees, but couldn't find it.
Do you know if by any chance it can auto-land on roofs?

I assume it can but there's one thing that needs to be cleared up. You said in the OP,  "All i know is that the drone never came back but i've seen it going down in the area where it lost the signal!"

If you mean you actually saw it going down, was it in free fall or was it a controlled descent as in AutoLand?

Roman Aitch Posted at 3-18 08:12
Thanks alot for you detailed analysis, it is really helpfull!
@Labroides and you both pointed out that the battery was not at 98%

Hi,

Second flight of the day, nothing wrong with going for a second flight starting at 54%.
As the batt values not that bad, i wrote that it did land   not dropping out of the sky and crashed!   :-)
( will happen for sure if batt cell values < 2.8 volts! )
Nah, understand your text wrongly, first flight it landed...second flight is still the question.But imo it did land 'somewhere'....

But why did it land at position where you lost connection the first flight  ??  it should do a RTH !  or your setting was "LAND" and not GoHome.  
Well now we know that a Mavic2 drops its battery from 95% to 54 in about an hour wating for its pilot to be found....   :-)

Did you changed the FailsSave setting for the second flight?  (as is the second flight the RTH failsafe setting is GoHome)

cheers
JJB

Roman Aitch Posted at 3-18 07:36
I did check the trees, but couldn't find it.
Do you know if by any chance it can auto-land on roofs?

It could land on flat rooves but I do not know if it might reject a landing site on a sloping roof.

Sean-bumble-bee Posted at 3-18 08:47
It could land on flat rooves but I do not know if it might reject a landing site on a sloping roof.

if it rejects a landing site it will cancel the landing and hover and wait and wait and.....    ;-)

JJB* Posted at 3-18 08:40
Hi,

Second flight of the day, nothing wrong with going for a second flight starting at 54%.

The first time, he found the drone almost directly under where the disconnect happened, which suggests to me that the drone is set to Land instead of RTH, unless I'm missing something.

Prairie Chicken Posted at 3-18 08:24
I assume it can but there's one thing that needs to be cleared up. You said in the OP,  "All i know is that the drone never came back but i've seen it going down in the area where it lost the signal!"

If you mean you actually saw it going down, was it in free fall or was it a controlled descent as in AutoLand?

It's wasn't falling, it was going down before i couldn't see it anymore!

- have no clue how far it landed from it last position
or if it ended up on a flat roof (there are some actually)

- i tried to turn off / on the remote as i did on first flight
but the connection was gone and i couldn't connect to it.

JJB* Posted at 3-18 08:40
Hi,

Second flight of the day, nothing wrong with going for a second flight starting at 54%.

I don't remember ever messing with those parameters..
But an important thing i can say is that with original mavic batteries
he always used to return home after a signal issue (when i was too far for instance)

JJB* Posted at 3-18 08:56
if it rejects a landing site it will cancel the landing and hover and wait and wait and.....    ;-)

until the low battery RTH kicks in and then it will RTH, tested with a Mavic Mini by switching the controller off and wwaaaiiiitttiiiiinnnnnggggg lol

Sean-bumble-bee Posted at 3-18 10:12
until the low battery RTH kicks in and then it will RTH, tested with a Mavic Mini by switching the controller off and wwaaaiiiitttiiiiinnnnnggggg lol

oke....

if understand it correctly....

• Failsafe setting to Land,
• Out of control (no connection),
• Landing
• Refuse to land due to unsafe area,
• Waiting for pilots input...(no connection so wait and wait...)
• Low battery triggers RTH and it will go to HP (with failsafe setting at Land) ??
  

cheers
JJB

I think so, although my test was with failsafe option set to "hover".
I switched the controller off and the drone hovered until the low battery level threshold was reached then it started to RTH, I then switched the controller back on.
I see no reason why it would differ just because the original setting was "land".