Has anybody ever had this happen to them?

[Kbviper]

I was flying my M2P with a battery that showed about 3/4 full on the green LED lights on the battery, it may have discharged some power automatically over the previous day, when all of a sudden, right after take off but I was already about 200 yards away, the phone display showed me 0% battery and the alarm went off. Needless to say I almost panicked since I had a river to cross and there were buildings in the area, I thought it was going to go into auto-land. I made it over the river and basically emergency landed it between a park bench and the river, almost landing diagonally. The battery still shows 3/4 full with the green lights, but on the phone display it shows 0%.

Are you not supposed to fly batteries after they have discharged to being idle, without re-charging them first? I am assuming the automatic discharge must have had something to do with this incident, even though I have flown discharged batteries without problems before.

I still don't know if the battery is actually 3/4 full or empty. I haven't tried to fly again with this battery, but will probably do a test soon. I did fly with another battery, and it worked fine.

Can somebody shed some light on this?

I had a very similar thing happen with a Mavic Enterprise Zoom (Which is a really a modified version of the Mavic 2) on Nov. 17th, 2019. I was visiting relatives in Nova Scotia and decided to launch off a cliff over looking a breakwater, wharf and a number of fishing boats.

There was a fairly strong wind in my face and I took off and put both sticks full forward, traveling forward and up into the wind. I took off with 97% battery, the battery had been charged 53 times, and I had been monitoring it in Airdata - no swelling or other issues.

I started getting the following warning: Not Enough Force/ESC Error (repeated 100 times)

Followed by: Mode changed to Confirm Landing

I was at an altitude of 319 feet, and 930 feet from the takeoff point, and out over the water.

The drone immediately started descending. I pushed the left stick forward in attempt to stop the descent, similar to what I have done with a critically low battery, but it kept descending, and the battery percentage was showing as 0%.

I started back towards the takeoff point, but it was quickly apparent that I would not make it back before the rate of descent put me down. There was a breakwater made out of triangular concrete pieces I flew along knowing that if I went down on it I would likely severely damage the drone, or possibly end up in the water, but at least there may be a chance to recover it.

As can be seen in the attached screenshot mapping the flight, as I got close to shore over the breakwater I turned to the right and put it down hard and fast into a sandy beach. No visible damage to the drone, but a lot of time ensuring that there was no sand left anywhere in it and extremely grateful that I recovered the drone and did not have to ditch it in salt water. The battery was permanently taken out of service.

As far as cause, I have a couple of thoughts - a defective battery, combined with an over load from full acceleration (up and forward) into a strong wind overwhelmed the battery. I have had the "Not Enough Force/Esc warning before and after this incident and now always let off as soon as I get it.

I have attached some screenshots of the flight from Airdata.

Looking at the battery data, it looks like two of the four cells were putting out very low voltage, but then recovered, however the battery display remained at 0% and the descent continued to the "controlled crash".

 

[Galeforce1]

I always upload the flight data immediately after each flight to Airdata (free account), where you can then take a good look at every aspect of your flight, including the health of your batteries. It is well worth doing so that you have the peace of mind of knowing exactly how your drone is performing at all times.

 

[PunaPhantom]

Strange coming across this post today... just got an email back from DJI Repair, my bird (Obsidian) is coming to roost after she dropped out of the sky (from 160 ft) - we do a preflight check and so all was completely in order... and airdata showed that the battery went from 99% to 0% in 7 minutes... DJI again comes through for us... after analyzing the logs, they will replace bird & battery at no cost...

 

[conchman]

Push and hold the battery button (not in aircraft) until lights come on.
If you have four lights, you have 100% battery life. If you have three lights, you have a battery that is only 75% life left. This sequence is indicating battery life, not charge state.

I am confused, what is the difference between battery life and charge state? When I press the button on the battery, the number of lights is showing how much the battery is charged, like 3 green lights mean about 75% charged. This is different from 'battery life?'

 

[DanMan32]

Battery life as in age. As I'm sure you know, as batteries are used, their capacity decreases.

Not sure if life status is based solely on charge count, or if available capacity is being measured. Could be both.

 

[Cymru]

This could be a cell being unbalanced or dead. They'll display a good voltage when under no load so look fine on the lights but drop instantly the second any sort of load is applied to them.

Mavic 1 in auto discharge was really bad for unbalancing cells, the M2 is better but it can still happen.

FWIW i had a battery drop from 96% to 0% in 32 seconds recently due to a cell crashing down on takeoff. The drone entered critical battery autoland.

 

[Dobmatt]

This could be a cell being unbalanced or dead. They'll display a good voltage when under no load so look fine on the lights but drop instantly the second any sort of load is applied to them.

Mavic 1 in auto discharge was really bad for unbalancing cells, the M2 is better but it can still happen.

FWIW i had a battery drop from 96% to 0% in 32 seconds recently due to a cell crashing down on takeoff. The drone entered critical battery autoland.

That's true indeed. The so called "battery life indicator" is useless with no load. The one and only, relatively reliable way to estimate the battery health is to observe individual cells voltage drop under heavy load during flight. There's a dedicated page in DJI Go 4 app to do just that. The best way to avoid surprising sudden power drops mid-flight is to fully charge just hours before planned flight and keep 60-65% charge for whatever time in between.

 

[Cymru]

This is what a sudden cell failure looks like on logs.
4th flight of the day, battery had been fully recharged some 3 hours previously.

You can see what i mean about voltage vs load on the second image. Low voltage warnings and drop in the climb and a *recovery* of voltage once descent was begun and the power load reduced.




So after 32 seconds of high load (take off power and climb away) it drops from 96% to 0% and immediately enters critical battery autoland.
Logs also stopped recording for some reason prior to landing.

So really don't rely on battery lights or the percentage indicator. Its good practice to test things like full power and speed right next to the take off point in case theres an issue.

Battery has 69 total cycles and no warnings or cautions prior to this flight.

 

[Dobmatt]

This is what a sudden cell failure looks like on logs.
4th flight of the day, battery had been fully recharged some 3 hours previously.

You can see what i mean about voltage vs load on the second image. Low voltage warnings and drop in the climb and a *recovery* of voltage once descent was begun and the power load reduced.


View attachment 119355

So after 32 seconds of high load (take off power and climb away) it drops from 96% to 0% and immediately enters critical battery autoland.
Logs also stopped recording for some reason prior to landing.

So really don't rely on battery lights or the percentage indicator. Its good practice to test things like full power and speed right next to the take off point in case theres an issue.

Battery has 69 total cycles and no warnings or cautions prior to this flight.

View attachment 119356

View attachment 119357

This is exactly what I'm talking about and should be reflected on DJI Go 4 battery state page, assuming you'll stare at it at this particular moment. The battery is ready to retire, useless to say ...

 

[Thomas B]

This is exactly what I'm talking about and should be reflected on DJI Go 4 battery state page, assuming you'll stare at it at this particular moment. The battery is ready to retire, useless to say ...

My experience with the one failed battery I had was that it failed suddenly about 30 seconds after TO. Got the drone down and the battery, which I had checked immediately preflight w/o abnormality, was obviously bulged.

Point. It’s only under load that these things manifest.

 

[Dobmatt]

My experience with the one failed battery I had was that it failed suddenly about 30 seconds after TO. Got the drone down and the battery, which I had checked immediately preflight w/o abnormality, was obviously bulged.

Point. It’s only under load that these things manifest.

Battery may fail to deliver without puffiness. None of mine (some 5 years old) get obese, yet they refuse to output ...

 

[conchman]

I was flying my M2P with a battery that showed about 3/4 full on the green LED lights on the battery, it may have discharged some power automatically over the previous day, when all of a sudden, right after take off but I was already about 200 yards away, the phone display showed me 0% battery and the alarm went off. Needless to say I almost panicked since I had a river to cross and there were buildings in the area, I thought it was going to go into auto-land. I made it over the river and basically emergency landed it between a park bench and the river, almost landing diagonally. The battery still shows 3/4 full with the green lights, but on the phone display it shows 0%.

Are you not supposed to fly batteries after they have discharged to being idle, without re-charging them first? I am assuming the automatic discharge must have had something to do with this incident, even though I have flown discharged batteries without problems before.

I still don't know if the battery is actually 3/4 full or empty. I haven't tried to fly again with this battery, but will probably do a test soon. I did fly with another battery, and it worked fine.

Can somebody shed some light on this?

Below is the screenshot video of the flight. The battery was one if three that got overheated in a car one time, but this particular battery was not bulged like the other 2 but probably still damaged from the event. As you can see, battery level goes from 96% to 0% instantly, after critical voltage error shoes up. After recharging the battery, everything looks normal but now I'm afraid to use it.

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[Dobmatt]

Below is the screenshot video of the flight. The battery was one if three that got overheated in a car one time, but this particular battery was not bulged like the other 2 but probably still damaged from the event. As you can see, battery level goes from 96% to 0% instantly, after critical voltage error shoes up. After recharging the battery, everything looks normal but now I'm afraid to use it.

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Battery Care is More Important than You Think - DJI Guidesstore.dji.com › ... › Tips & Tutorials › Product use & care

Rule #1: Always charge the battery fully just hours before planned flight.
Rule #2: Always keep the battery 55-60% charged for the remaining storage time longer than 2-3 days.
Rule #3: Don't rely 100% on self-discharge feature. It's only a last resort solution for careless/filthy rich people.
Rule #4: Read Rule #1 again.
Rule #5: Read Rule #4 again...

 

[conchman]

You're saying 97% charge was not sufficient? It probably just lost a few percent over a day or two after being fully charged. That cannot be the problem here, it would seem.

Battery Care is More Important than You Think - DJI Guidesstore.dji.com › ... › Tips & Tutorials › Product use & care

Rule #1: Always charge the battery fully just hours before planned flight.
Rule #2: Always keep the battery 55-60% charged for the remaining storage time longer than 2-3 days.
Rule #3: Don't rely 100% on self-discharge feature. It's only a last resort solution for careless/filthy rich people.
Rule #4: Read Rule #1 again.
Rule #5: Read Rule #4 again...

 

[Dobmatt]

You're saying 97% charge was not sufficient? It probably just lost a few percent over a day or two after being fully charged. That cannot be the problem here, it would seem.

In contrary, it may be a problem if a pre-determined auto discharging procedure kicked in just in the middle of this particular flight. I may be wrong, I've been wrong before. Logically thinking, the act of powering should cancel auto discharge timing, but ... All I know for sure is that topping the battery a day before planned mission will reset auto discharging timer, making sure the battery will not enter the discharge state for next 2 days or whatever period was determined by FW. I'm not even sure if it's 2 days or more, please research the issue of auto discharge for your batteries.

 

[Thomas B]

In contrary, it may be a problem if a pre-determined auto discharging procedure kicked in just in the middle of this particular flight. I may be wrong, I've been wrong before. Logically thinking, the act of powering should cancel auto discharge timing, but ... All I know for sure is that topping the battery a day before planned mission will reset auto discharging timer, making sure the battery will not enter the discharge state for next 2 days or whatever period was determined by FW. I'm not even sure if it's 2 days or more, please research the issue of auto discharge for your batteries.

I don’t believe auto discharge can begin during a flight. However, I too off all batteries immediately (w/in24 hrs) of planned flight. This optimizes everything regarding battery power available.

 

[Dobmatt]

"I don’t believe auto discharge can begin during a flight"

True, but I've seen a thing or two DJI branded that were behaving not as intended by a FW ...

 

[Thomas B]

"I don’t believe auto discharge can begin during a flight"

True, but I've seen a thing or two DJI branded that were behaving not as intended by a FW ...

True...

 

[conchman]

I did a test flight with that battery today, and everything worked normal. Still scared to use it though. I did find option to put voltage indicator on phone screen, that may or may not give me a warning before the instant 0% battery life error pops up.

 

[Cymru]

I did a test flight with that battery today, and everything worked normal. Still scared to use it though. I did find option to put voltage indicator on phone screen, that may or may not give me a warning before the instant 0% battery life error pops up.

Mine didnt...