Phantom 4 - Sudden crash

[Pontus Wolf]

Hello, fellow pilots!

Here is a sad story for you:

I took out my Phantom 4 for the first time in four months, due to the cold winter we have here in Sweden.
I planned to make a short run to check for any updates and the condition of the batteries. The weather was still cold at 3°C (37°F), sunny and a slight breeze.

I had 40% battery charge, but since I only planned to be up for five minutes, I thought it would be OK.
I should perhaps mention that I have flown my drone for over five years in various conditions without serious issues.

I ascended to about 40 meters and then flew 47 meters NE over a neighboring empty lot. I hovered there and while looking at the screen, started a slow pan to the right. A few seconds later the image started to wobble, and when I looked up I saw my drone drop like a stone to the ground.
The drone took some serious beating—one arm broke off completely as well as the camera, but …the battery was still securely in place.
I checked the flight log and couldn't see any obvious reason for the crash, I still had 35% battery left.

I would appreciate your thoughts or ideas as to why this happend.

I'm grateful for the years I had with my white angel, but it was perhaps her time…

I've attached the flight log for your perusal.

 

[Meta4]

I had 40% battery charge, but since I only planned to be up for five minutes, I thought it would be OK.

The sad part of the story is that you didn't have 40% battery.
The % indicator cannot be relied on when the battery has been sitting around and discharging.

Here's a summary of the flight data:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

Note how all battery cells are reaching critical low voltage level only 22 seconds into the flight, when you are climbing.
That doesn't happen with a genuine 40% battery.

At 34 seconds there is another warning that the battery is in trouble:
Battery power limit will automatically reduce the aircraft's mobility to ensure flight safety.

You should only fly with a freshly charged battery.
Launching with one that's been sitting around for some time is asking for trouble.

 

[Pygar70]

The sad part of the story is that you didn't have 40% battery.
The % indicator cannot be relied on when the battery has been sitting around and discharging.

Here's a summary of the flight data:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

Note how all battery cells are reaching critical low voltage level only 22 seconds into the flight, when you are climbing.
That doesn't happen with a genuine 40% battery.

At 34 seconds there is another warning that the battery is in trouble:
Battery power limit will automatically reduce the aircraft's mobility to ensure flight safety.

You should only fly with a freshly charged battery.
Launching with one that's been sitting around for some time is asking for trouble.

Are you saying that the voltage level does not drive the battery % charge reading? If that's the case, how is the reading derived?
Normally the drone would make a controlled descent, or rather, not have taken off in the first place. Did that not happen because the app didn't register that the battery was depleted?

 

[Meta4]

Are you saying that the voltage level does not drive the battery % charge reading? If that's the case, how is the reading derived?
Normally the drone would make a controlled descent, or rather, not have taken off in the first place. Did that not happen because the app didn't register that the battery was depleted?

If you have a battery that's been discharging for weeks, like this one was, the % indication will be false.
A healthy battery with a genuine 40% doesn't sag to critical low voltage levels (3.2 volts per cell) when you push the left stick up.
There have been many cases of drones launched with discharged batteries falling from the sky.

 

[DoomMeister]

LiPo cells that have been sitting for months are much like a car battery that has been sitting for months. Both may have an acceptable voltage reading when measured without an appreciable load connected to them, but once you start trying to draw a high amperage load the voltage drops to a level that cannot support the device. In the case of the drone the motors are starved and lift drops precipitously. With the car battery the starter motor is unable to generate enough momentum to start the engine.

This is why it is always recommended to takeoff with full freshly charged batteries.

 

[Andy9]

I think that the moment the first warning appeared was the last to immediately land.
The battery with the starting voltage so low it is enough that the voltage of one cell drops below critical value as has been said and triggers the battery to shut down. This was discussed here several times why this programmed shutdown has any sense in the case of drones. Why protect the battery instead of the drone? But this is the technology I guess.

 

[Fabian Sylvester]

Hello, fellow pilots!

Here is a sad story for you:

I took out my Phantom 4 for the first time in four months, due to the cold winter we have here in Sweden.
I planned to make a short run to check for any updates and the condition of the batteries. The weather was still cold at 3°C (37°F), sunny and a slight breeze.

I had 40% battery charge, but since I only planned to be up for five minutes, I thought it would be OK.
I should perhaps mention that I have flown my drone for over five years in various conditions without serious issues.

I ascended to about 40 meters and then flew 47 meters NE over a neighboring empty lot. I hovered there and while looking at the screen, started a slow pan to the right. A few seconds later the image started to wobble, and when I looked up I saw my drone drop like a stone to the ground.
The drone took some serious beating—one arm broke off completely as well as the camera, but …the battery was still securely in place.
I checked the flight log and couldn't see any obvious reason for the crash, I still had 35% battery left.

I would appreciate your thoughts or ideas as to why this happend.

I'm grateful for the years I had with my white angel, but it was perhaps her time…

I've attached the flight log for your perusal.

Good afternoon.

I had two 'fall-from-skies' like you did but it turned out to be that that battery was faulty as it had major voltage deviations in cell 4 (when a cell differs more than 0.07v from the other cells). The DJI Go app does not have the ability to indicate this and the drone gives no warning of its own. It was only after flight analysis from Drone Data Management and Flight Analysis | Airdata UAV that I was educated about this. According to them:
“An abnormal battery will:
A) Have most of the major deviations in one cell
B) There will be multiple major deviations per minute, and more than 10 total
C) The deviations continue longer than 1 minute
If your battery shows all symptoms (example, another) then this is considered a more severe case of an inefficient battery and may impact the battery life.”
MINE HAD ALL OF THE ABOVE!

First fall (Sep2019) was at 14% while Critical Level was set at 15%.
Second fall (Dec2019) was at 20% while Critical Level was set at 20%.

I did a personal experiment after to prove to myself that:
1. The battery was indeed faulty and/or
2. Opposing a drone’s attempt to land at Critical Level % (whatever it is) will cause it to power-cut and fall from sky.

METHOD: I fully charged the battery, set the Low Battery level at 20% and the Critical Level at 10%. I hovered it just a couple of meters over some soft high grass (to allow for a non-damaging fall), and allowed the battery to dissipate. The EXPECTATION was that it will attempt to Return To Home at the Low Level of 20% where I would override it, then it would attempt to land at 10% where I would oppose it (by pitching, rolling and throttling). At this point I would’ve expected to lose power and fall from the sky. INSTEAD, it began beeping (Critical beep) at a whopping 25% and began its vertical descent. As I gave it a little throttle to keep it from descending and a little left roll to get over some higher grass, it cut off and fell to ground at 24%.
So indeed that battery was faulty and I discarded it.

Just for further information on item #2 above, I did another experiment with my other good battery to see if the value of the Critical Level % has anything to do with the bird cutting power and falling from sky. I set Low at 50% and Critical at 40% and hovered. I overrode its RTH when it reached Low 50%, opposed its landing when it reached Critical 40%, and it didn’t lose power and fall. It fought me all the way down to 15% where I finally allowed it to land. (I suspected it would've fallen at 10% and regret I didn't allow it to reach there to see).

 

[Meta4]

Good afternoon.

I had two 'fall-from-skies' like you did but it turned out to be that that battery was faulty as it had major voltage deviations in cell 4 (when a cell differs more than 0.07v from the other cells). The DJI Go app does not have the ability to indicate this and the drone gives no warning of its own. It was only after flight analysis from Drone Data Management and Flight Analysis | Airdata UAV that I was educated about this. According to them:

The % indication doesn't matter to the battery and drone, it's the actual cell voltages that matter.
Airdata is overly conservative in their definition of major deviation and small deviations (larger than 0.07V) in cell voltage aren't likely to cause a drone to fall from the sky.

 

[Fabian Sylvester]

The % indication doesn't matter to the battery and drone, it's the actual cell voltages that matter.
Airdata is overly conservative in their definition of major deviation and small deviations (larger than 0.07V) in cell voltage aren't likely to cause a drone to fall from the sky.

Well in my case, at the time of my second crash, these were my voltages:
Cell 1 - 3.465 V
Cell 2 - 3.325 V
Cell 3 - 3.373 V
Cell 4 - 2.926 V

Compared to the next lowest cell (#3), that deviation is 5.7 times higher than what they see as a major deviation.

 

[Fly With Me]

The sad part of the story is that you didn't have 40% battery.
The % indicator cannot be relied on when the battery has been sitting around and discharging.

Here's a summary of the flight data:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

Note how all battery cells are reaching critical low voltage level only 22 seconds into the flight, when you are climbing.
That doesn't happen with a genuine 40% battery.

At 34 seconds there is another warning that the battery is in trouble:
Battery power limit will automatically reduce the aircraft's mobility to ensure flight safety.

You should only fly with a freshly charged battery.
Launching with one that's been sitting around for some time is asking for trouble.

I thought that you should only charge P4 batteries if they were fully discharged. Should you charge batteries when they are that are partially discharged? How do I fully discharge a battery unless I am flying?

 

[Pontus Wolf]

Hello again,

Thank you Meta4 for your concise diagnosis.

When I checked my Flight Log after the crash I saw the low voltage and the warnings, and guessed it had to be some problem with the battery, I just couldn't figure exactly what it was.

I always charge my batteries fully before flying, except for this one time. I can't really understand myself, why I didn't charge the battery this time. I guess I thought (Like Pygar70) that my bird would land automatically at low battery level, like it is programmed to do.

Well, lesson learned… Hindsight is 20-20.

The only consolation is that other pilots may learn from my mistake…

Still, it could have been much worse. At least I was over an empty lot. I'll miss my Phantom, she was a solid and stable companion, and now I know it wasn't her fault.

However, due to the upcoming drone regulations in EU concerning remote ID, she would probably have been obsolete next year. Old drones must then keep at least 150 meters from roads, buildings etc.

Anyway, thank you all for your valuable information and for sharing your stories.

 

[Meta4]

I thought that you should only charge P4 batteries if they were fully discharged.

I'm not sure where that idea came from, but it's certainly not true.
You can safely top up the battery from any charge level.

Should you charge batteries when they are that are partially discharged? How do I fully discharge a battery unless I am flying?

There's no need to fully discharge the battery.
The battery will self-discharge to storage level automatically.

 

[Meta4]

Well in my case, at the time of my second crash, these were my voltages:
Cell 1 - 3.465 V
Cell 2 - 3.325 V
Cell 3 - 3.373 V
Cell 4 - 2.926 V

Compared to the next lowest cell (#3), that deviation is 5.7 times higher than what they see as a major deviation.

That was a major deviation and likely an indication of a problem with that cell.

 

[Andy9]

It is better to periodically check the status of the battery with the Airdata or similar webpage. I do this very often to see how the battery behaves during the flight. I found it very useful. You can change the faulty battery before it does any harm.
I have set the LBL at 30% and the critical level at 10%. I try not to reach the last one and land before that. Usually at 25%.

 

[evets]

Hello, fellow pilots!

Here is a sad story for you:

I took out my Phantom 4 for the first time in four months, due to the cold winter we have here in Sweden.
I planned to make a short run to check for any updates and the condition of the batteries. The weather was still cold at 3°C (37°F), sunny and a slight breeze.

I had 40% battery charge, but since I only planned to be up for five minutes, I thought it would be OK.
I should perhaps mention that I have flown my drone for over five years in various conditions without serious issues.

I ascended to about 40 meters and then flew 47 meters NE over a neighboring empty lot. I hovered there and while looking at the screen, started a slow pan to the right. A few seconds later the image started to wobble, and when I looked up I saw my drone drop like a stone to the ground.
The drone took some serious beating—one arm broke off completely as well as the camera, but …the battery was still securely in place.
I checked the flight log and couldn't see any obvious reason for the crash, I still had 35% battery left.

I would appreciate your thoughts or ideas as to why this happend.

I'm grateful for the years I had with my white angel, but it was perhaps her time…

I've attached the flight log for your perusal.

You should always fly on full battery flying from 40% after storage probably caused the problem. Should always fully charge after storage.

 

[dcjohnson]

My Phantom Four just fell out of the sky, too. It had a newly purchased replacement battery charged two days ago, showing 4 bars. DJI 4.0 indicated 33% left on the charge. As I was bringing it down it suddenly shut off and fell to the ground causing severe damage to the landing runners and gimbal.

My post is more of a warning about cheap batteries. I knew better, but took the chance. Heavy sigh....

FYI: Purchased from Amazon, two batteries for $169.99 USD. UAV Electronic Mall model number: FB1-5870mAh-15.2v.

 

[Meta4]

My Phantom Four just fell out of the sky, too. It had a newly purchased replacement battery charged two days ago, showing 4 bars. DJI 4.0 indicated 33% left on the charge. As I was bringing it down it suddenly shut off and fell to the ground causing severe damage to the landing runners and gimbal.

My post is more of a warning about cheap batteries. I knew better, but took the chance. Heavy sigh....

It would be interesting to see the flight data and what it tells about the incident.
It might not be what you've guessed.

Go to DJI Flight Log Viewer | Phantom Help
Follow the instructions there to upload your flight record from your phone or tablet.
That will give you a detailed report of the flight.
Come back and post a link to the report it gives you.
Or .. just post the txt file here.

 

[dcjohnson]

It would be interesting to see the flight data and what it tells about the incident.
It might not be what you've guessed.

Go to DJI Flight Log Viewer | Phantom Help
Follow the instructions there to upload your flight record from your phone or tablet.
That will give you a detailed report of the flight.
Come back and post a link to the report it gives you.
Or .. just post the txt file here.

Hmmm... looks like one cell is having trouble, but not sure that caused the crash!
First flight on new battery:
DJI Flight Log Viewer - PhantomHelp.com
Second flight when drone crashed:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

 

[Meta4]

Hmmm... looks like one cell is having trouble, but not sure that caused the crash!
First flight on new battery:
DJI Flight Log Viewer - PhantomHelp.com
Second flight when drone crashed:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

Neither of those flights shows any problems with cell voltages.
Your crash data shows the drone in steady, hands-off autolanding with the data just stopping with the height at 172 ft.
Rather than a cell having trouble, the issue was a sudden, complete power loss.
The data doesn't show what could have caused this but it would have been either a hardware failure or the battery connection being dislodged.

 

[dcjohnson]

Neither of those flights shows any problems with cell voltages.
Your crash data shows the drone in steady, hands-off autolanding with the data just stopping with the height at 172 ft.
Rather than a cell having trouble, the issue was a sudden, complete power loss.
The data doesn't show what could have caused this but it would have been either a hardware failure or the battery connection being dislodged.

I'm leaning towards a hardware failure. However, I can't help but think there might be something more nefarious going on here... puts on tinfoil hat.

I'm sending the drone to DroneRepair in LA tomorrow. Maybe they will look for something like that.

Thank you for your input! Really appreciate it...