Took my Mavic Pro out for a flight last night. It was perfectly calm evening and was not experiencing any issues at all beforehand. I did an initial quick flight and still had a lot of battery left, or so I thought, so I decided to take it up for another quick flight. I was doing a loop out around the lake and was starting to turn to come home. All of a sudden my battery level dropped from around 30% to about 10% within seconds and the Mavic started autolanding. I have the video from the DJI Go 4 app () and the flight record (http://www.phantomhelp.com/LogViewer/P9C8ORYCXD3A9OLR6HTC/) and from the flight record it seems that Cell #3 started depleting very rapidly and the battery failed. From the video, at the last few seconds you can see a pretty significant wobble and a slight tilt to the left before video cuts out, which to me implies that the drone lost power and started to fall.

Anyhow I'm bummed out about this. Went out searching for the drone and I have an idea of where it might be but it's an area with thick tree cover and I haven't been able to spot it yet. I guess it's probably stuck up in a tree and I might not be able to see it until autumn time when the trees drop their leaves. I have my FAA stickers and contact info on it so hopefully if someone finds it they'll contact me.

Anyhow I just wanted to share this. Expensive lesson to learn - check your battery condition periodically during flights and don't trust the battery bar at the top of the DJI Go app. I welcome any thoughts or insights others may have about what happened or why.

You should never take off with anything but am100 percent charged battery. Sorry to hear this happened.

Sorry to read about another lost bird. Hope someone finds it and contacts you.

Sorry you lost your bird.

Did you try using this application in your Dji Go 4 App?

Thats bad luck.   Looking at those logs it looks like a clear case of a cell failure in the battery with no warnings before the event so not your fault or anything you can do.

Yes you took off at 60% but thats not the issue here, you have no way of knowing when a cell will go down.  Could happen at 40,50.60 or whatever.

Make sure DJI are aware of this - theres a good cause for a replacement based on that.  No user error.
It does look like it eventually ran out of power and dropped.  It could well be stuck in a tree - the things are light and often cant punch through foliage.

Lonesome Crow Posted at 2018-8-11 05:04
Did you try using this application in your Dji Go 4 App?

[view_image]

Unfortunately the aircraft disconnected right at the end of the video and I never could get it to reconnect.

Your flight log shows it was auto landing and last located at 38.93424378, -77.3276739. It should be close to that location. Plug those GPS coordinates into a map app on your mobile device and you'll likely find it.

Sorry for your loss. Definitely looks like a battery failure. Taking off at 60% is no problem and you shouldn't be scolded for that. How could you have know that this would happen at 60% or 100%. Looks like you were at 160' when things cut out, so that'd be a long way to fall if the battery cut out. Could be in the top of a tree or house based on the GPS map. If you find it, it'll probably need a trip to DJI repair to fly again.

Sorry about that, from looking at your log my question to you would be is when last have you flown the drone? if it was a couple of days ago it seems that your battery has entered into discharge mode hence the rapid decrease in battery/cell power while flying. It is always recomended to fully charge your battery before flight and to check the cell power.

sorry for your loss and I am hoping that you will be able to find it.

Suren Posted at 2018-8-11 06:59
Sorry about that, from looking at your log my question to you would be is when last have you flown the drone? if it was a couple of days ago it seems that your battery has entered into discharge mode hence the rapid decrease in battery/cell power while flying. It is always recomended to fully charge your battery before flight and to check the cell power.

Actually that is a point.  I have found once the batteries enter the self-discharge state (10 day default) they don't discharge the cells simultaneously or evenly.  I very frequently get cell errors and such even though the battery shows as charged after that.
The only way i can cure it, if i know its started discharging is turn the battery ON (not in the drone) then back off then charge.
Without that step, putting it on the charger it doesnt match cells.

However, i dont think its the issue here - the start of the flight things are showing balanced and in step then suddenly goes towards the end.  That to me is more a sign of a physical failure of a cell and resulting loss of drone.

Its one of the clearer "crash not by user error" ive seen on this forum for a while.

Paul_IA Posted at 2018-8-11 06:18
Sorry for your loss. Definitely looks like a battery failure. Taking off at 60% is no problem and you shouldn't be scolded for that. How could you have know that this would happen at 60% or 100%. Looks like you were at 160' when things cut out, so that'd be a long way to fall if the battery cut out. Could be in the top of a tree or house based on the GPS map. If you find it, it'll probably need a trip to DJI repair to fly again.

Taking off at 60% battery is a problem particularly if that 60% is due to battery going into discharge, which will almost never give you 60%, when starting a mission you should always start with 100% freshly charged battery.

Check and follow those last known GPS coordinates and survey the area thoroughly would be my suggestion.  Something similar happened to my MP once and I pointed the camera down, familiarized myself with the location landed in an open area and picked up the drone there - it was about a half mile away from the original home point.

hallmark007 Posted at 2018-8-11 07:47
Taking off at 60% battery is a problem particularly if that 60% is due to battery going into discharge, which will almost never give you 60%, when starting a mission you should always start with 100% freshly charged battery.

I did 2 flights yesterday. The first one started with a battery at 100%. I came home, landed for a few seconds, then decided to fly again.

The first flight was about 10 minutes and then came home. I still had 62% left after that flight (logs http://www.phantomhelp.com/LogViewer/PR3YMLBJK3XOKAWA60K2/). This flight was uneventful and everything went normally.

So I decided to go up again for another quick flight. That second flight is the one I posted above. The battery appears to have died midflight when I was turning to come home.

Suren Posted at 2018-8-11 06:59
Sorry about that, from looking at your log my question to you would be is when last have you flown the drone? if it was a couple of days ago it seems that your battery has entered into discharge mode hence the rapid decrease in battery/cell power while flying. It is always recomended to fully charge your battery before flight and to check the cell power.

It was last flown about a week ago but I pulled the battery off the charger right before I flew last night and it was fully charged. The flight log I posted above showed the battery at 60% because I did 2 flights - the first one is here: http://www.phantomhelp.com/LogViewer/PR3YMLBJK3XOKAWA60K2/

Flew for about 10 minutes and then landed briefly. My neighbor came out and asked me about the drone so since I had 60% battery left I took it up and flew it around to show it to him. That's the second flight that I posted where I lost the drone: http://www.phantomhelp.com/LogViewer/P9C8ORYCXD3A9OLR6HTC/

Thank you all for your insights so far.

S.D. Pilot Posted at 2018-8-11 08:08
Check and follow those last known GPS coordinates and survey the area thoroughly would be my suggestion.  Something similar happened to my MP once and I pointed the camera down, familiarized myself with the location landed in an open area and picked up the drone there - it was about a half mile away from the original home point.

Yeah I've been over to that spot a few times last night and this morning. Knocked on a few doors, introduced myself to new friends. Told them the story. It's a lot of tree cover in the area where the last know GPS coordinates are located so my guess is that it's up in one of those trees and I can't see it.

I brought my controller over to that area last night right after this happened thinking that if it auto-landed in a tree it might still have some battery life left and I'd be able to reconnect with it. No luck there. It looks like the battery cut out completely which is why the wobble in the video at the same time as the disconnect - I think it totally lost power and dropped out of the air. My guess is that it's up in one of those trees near where it last reported its location.

If it did drop with no power its less than 2 seconds to hit the deck from there so it wouldn't have drifted or moved more than 10-20m from that reported location.

Hey, watch this video from Ian in London.  Short, to the point, and might help.  I have discussed this before, and have actually practiced using it.  Highly recommend pilots practice this from time to time.  Thanks to Ian!

hallmark007 Posted at 2018-8-11 07:47
Taking off at 60% battery is a problem particularly if that 60% is due to battery going into discharge, which will almost never give you 60%, when starting a mission you should always start with 100% freshly charged battery.

His battery failed mate. Wouldn't have mattered if it was 60% or 100% in this scenario. Let's not cast fault on the pilot for a hardware error.

Duffman Posted at 2018-8-11 08:29
Yeah I've been over to that spot a few times last night and this morning. Knocked on a few doors, introduced myself to new friends. Told them the story. It's a lot of tree cover in the area where the last know GPS coordinates are located so my guess is that it's up in one of those trees and I can't see it.

I brought my controller over to that area last night right after this happened thinking that if it auto-landed in a tree it might still have some battery life left and I'd be able to reconnect with it. No luck there. It looks like the battery cut out completely which is why the wobble in the video at the same time as the disconnect - I think it totally lost power and dropped out of the air. My guess is that it's up in one of those trees near where it last reported its location.

Gotcha, yeah sounds like it's hanging out with a few branches. Hopefully those folks you spoke will give you a call if they find it before you do.

Paul_IA Posted at 2018-8-11 09:45
His battery failed mate. Wouldn't have mattered if it was 60% or 100% in this scenario. Let's not cast fault on the pilot for a hardware error.

How do you figure it was a hardware fault ?

Update: Drone recovered. Neighbor of the person I spoke to this morning found my drone and called me. It's back and damaged as Paul_IA suspected. It looks like it fell out of the sky, hit the roof, and tumbled into their flower garden. Interestingly, the battery was not in the drone when it was recovered, it was found several feet away.

Off to DJI it goes I guess.

Sorry for the loss.

If there wasn't a strong wind you were flying against it then the battery malfunction was the only reason for this case.

The battery's total time (100%) for both flights was only 16m:32s + (5%) and this is abnormal.

hallmark007 Posted at 2018-8-11 10:26
How do you figure it was a hardware fault ?

You may want to go back and take a look at the flight log he uploaded. At 14.42 he has 40% battery and it drains to 5% in less than 2 minutes.

Also note the increasing cell deviation in cell #3 during this time. You can decide if this is normal battery behavior yourself, but I wouldn't fly with a battery that exhibited that kind of discharge behavior.

If you think this isn't a bad battery, we'll just have to agree to disagree and move on.

Duffman Posted at 2018-8-11 10:30
Update: Drone recovered. Neighbor of the person I spoke to this morning found my drone and called me. It's back and damaged as Paul_IA suspected. It looks like it fell out of the sky, hit the roof, and tumbled into their flower garden. Interestingly, the battery was not in the drone when it was recovered, it was found several feet away.

Off to DJI it goes I guess.

The battery most likely just popped out on impact. Your battery failed just like this one https://forum.dji.com/thread-159346-1-1.html

Duffman Posted at 2018-8-11 10:30
Update: Drone recovered. Neighbor of the person I spoke to this morning found my drone and called me. It's back and damaged as Paul_IA suspected. It looks like it fell out of the sky, hit the roof, and tumbled into their flower garden. Interestingly, the battery was not in the drone when it was recovered, it was found several feet away.

Off to DJI it goes I guess.

Replying to add pic

Duffman Posted at 2018-8-11 10:42
Replying to add pic[view_image]

I tried to open the video file from the SD card to see what the Mavic saw when it crashed but the video is corrupted which I think lends credibility to the sudden loss of power theory.

Duffman Posted at 2018-8-11 10:52
I tried to open the video file from the SD card to see what the Mavic saw when it crashed but the video is corrupted which I think lends credibility to the sudden loss of power theory.

The video from the first flight is intact and plays just fine.

Duffman Posted at 2018-8-11 10:52
I tried to open the video file from the SD card to see what the Mavic saw when it crashed but the video is corrupted which I think lends credibility to the sudden loss of power theory.

sometimes the video disappairs because of not been finalized by the stop button before power off.

Duffman Posted at 2018-8-11 10:53
The video from the first flight is intact and plays just fine.

Yup if a video file is still being written to and not properly closed, the file header isn't written and the data is then hard to read without specialist forensic software.

Duffman Posted at 2018-8-11 10:42
Replying to add pic[view_image]

Definitely needs more than duck tape and drone plastic glue.  Bummer man.  

Cell #3's sudden deviation from Cell #1 and #2 in later part of Auto Landing is indication that Cell #3 has a problem.

With that said, it is still a good idea to start all flights out with 100% charged battery pack.  Being, you never know when Mother Nature is going to decide that nice outgoing breeeze of head wind will shift, and become a gail force head wind for return flight.

yep, with those coordinates it looked like it was heading for someone's roof.  That flight looks like it was inside the dulles class bravo surface area.

This is why you never take off without a battery being 100% charged.  Just another pilot air.

fansf77370fb Posted at 2018-8-13 06:34
This is why you never take off without a battery being 100% charged.  Just another pilot air.

Utter rubbish.

He was in the air with loads of battery left, well over what most people come back to land with and it dropped within seconds due to a faulty cell.

Or do you always make a point of landing with 60%+ battery remaining?

For all those saying 'Pilot Error' because OP took off with a battery that was not a 100% recharged, might want to consider most commercial aircraft flights do not take off with 100% fuel load.
There appears to be a problem with estimated amount of power (fuel) remaining in drone batteries for whatever reason.  Being these are ''''Smart'''' batteries, the electronics of battery should know starting point of last recharge vs. amount of power (fuel) used, and what is left.

Until system is fixed or improved, best to start all flights with 100% battery.  

Even starting with 100%, there is no guarantee the pilot won't experience a sudden drop in battery capacity.  There has been several cases posted here in past where power went from ##% to near 0% in seconds.  Yet when drone / battery were recovered, battery would show by LEDs roughly ##% capacity left.

HedgeTrimmer Posted at 2018-8-13 07:14
For all those saying 'Pilot Error' because OP took off with a battery that was not a 100% recharged, might want to consider most commercial aircraft flights do not take off with 100% fuel load.
There appears to be a problem with estimated amount of power (fuel) remaining in drone batteries for whatever reason.  Being these are ''''Smart'''' batteries, the electronics of battery should know starting point of last recharge vs. amount of power (fuel) used, and what is left.

I have on multiple occasions flown 2 separate flights with one battery. Even if the stated % left is a bit off (which I have not yet experienced), taking off with the same battery for a second flight is not going to cause a cell failure.