Recreated "falling from the sky" issue

[BigAl07]

This evening while doing my monthly battery testing I was able to "accidentally" recreate the falling out of the sky "dead" issue. I flew several different locations today and came home with some partially discharged batteries. The last day of the month I log all of my batteries and deep discharge any that are around the 20 cycle mark (20, 40, 60, 80 etc).

I had a battery that was at 47% and I wanted to run it down to less than 10% to initiate the Recalibration function of the Smart Battery. I was watching the actual battery statistics while hovering just above eye level. I wanted to see just how much difference putting a heavy load on this battery would do so I (don't repeat this at home it's not safe) took hold of the landing skid and applied more throttle. The motors revved hard but the battery indicator was barely showing red on one cell so I increased the throttle more. Tx immediately indicated "Critically Low Voltage" (still showing 45% capacity but voltage was red on every cell). Within about 2 seconds the aircraft completely powered down and had I not been holding the landing skid it would have tumbled to the ground.

So if you are trying to get a few more minutes by flying with a partially charge pack realize you could very easily cause a complete power-down.

Air temp was roughly 54degs so it was not a cold battery issue at all.

Good luck and fly safe.

 

[teeitup]

Which firmware?


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[BigAl07]

1.4.1 I believe. I didn't move up to 1.5 or 1.6

 

[Zerone]

Air temp was roughly 54degs so it was not a cold battery issue at all.

Actually, it could well have been battery temperature. Watch this battery test video.

 

[Mark The Droner]

Nice!

Let's paste the summary here:

20C is 68F

30C is 86F

35C is 95F

credit: hummingbird.UAV on youtube.com

 

[Mark The Droner]

edited out: redundant

 

[happydays]

The OP is talking about ambient temperature, I believe. The battery would have warmed up as it was used - the HD log would show the temperature of the battery, probably a good deal higher than ambient.

It would be interesting to replicate the test to see if it can be made to happen again, then test it using the same battery with 1.6 firmware that is supposed to stop this happening.

 

[Dirty Bird]

I think the most important lesson to take away from this is to always fly with a fully charged battery. This is especially important if ambient temps are below 70-75°.

 

[Mark The Droner]

The OP is talking about ambient temperature, I believe. ...

Yes, but if the ambient temp is 54F and the battery is 54F, you're already tempting fate from the very beginning, according to the video - since 57F is below 20C which is 68F.

 

[TheLightSpeedz]

Wow what a great video! That's exactly what happened to me when mine fell out of the sky. I had a partially charged battery, it was freezing outside. And boom it fell.


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[TheLightSpeedz]

I've noticed on 1.6 that in my area Seattle, where its been 38 to 45 degrees daily, that the thrust is cut back to a noticeable amount.


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[BigAl07]

Yes, but if the ambient temp is 54F and the battery is 54F, you're already tempting fate from the very beginning, according to the video - since 57F is below 20C which is 68F.

I should have left a few more details from the get-go.

As a side note: I've been flying R/C for 4 decades and working with LiPo for at least the last several years. I have over 40 different sizes and types of LiPo in my possession (I fly planks, helis and MRs) and normally fly in varied temps. I can say with almost certainty that flying a battery at 54 deg is not going to be a huge determining factor in LiPo performance. I've logged flights in temps as low as 18deg F just in the last month with zero battery issues. I do preheat my packs when I'm flying in colder temps but anything above 45 I don't fool with this. The battery comes up to operating temp very quickly once the motors are engaged.

Also the ambient temp (outside) was 54deg but the battery and aircraft had been inside my house for a couple of hours which remains 69/70 during normal waking hours. I am pretty sure the LiPo was not cool enough to be problem but the next opportunity I have I'll try and recreate it again. Also note that I had been hovering the aircraft and inspecting battery levels as opposed to powering up and immediately going into a high load climb. Battery would have been up to operating temperature very quickly even if it had not been inside at 70deg immediately prior to the flight.

Just for kicks-n-grins I'll try to get the Healthy Drones report on this incident tonight and when I do I'll upload that info here as well. This way it can be a valid learning experience and not just a hunch and a guess.

 

[tcope]

Actually, it could well have been battery temperature. Watch this battery test video.

While this is a very good video and provides some good information, it's not really on point with this thread. The video shows that a colder battery goes into critical state at a higher voltage. Okay... this has always been known about lipo batteries. They don't last as long when they are cold. While I understand you are pointing out that even slightly cool/cold batteries have reduced power, the video only points out when the critical state kicks in.

However, the OP's issue is that the battery turned _off_ when it was showing around 45%. This is the issue as a battery simply should not turn off at this point. If kept up with prior threads, we know that this was an issue prior to 1.6 firmware.

I've said this in past posts and I'll mention it again... _everyone_ should update to 1.6 firmware... even if they are not running 1.5 (that is, even if they are running 1.4 or older). You will most likely see a small reduction in over-all speed but the trade off.... you $1000 P3 will stand less of a chance of turning off while it's flying.

I will also highly recommend that people turn on the display voltage setting and monitor the _voltage_ not just the percentage of battery left. That percentage can be misleading. The over-all voltage is a much better gauge of the current charge state of the battery. I'd say the video then shows good information as to what voltage to look for for safe flying.

 

[tcope]

Also the ambient temp (outside) was 54deg but the battery and aircraft had been inside my house for a couple of hours which remains 69/70 during normal waking hours. I am pretty sure the LiPo was not cool enough to be problem but the next opportunity I have I'll try and recreate it again. Also note that I had been hovering the aircraft and inspecting battery levels as opposed to powering up and immediately going into a high load climb. Battery would have been up to operating temperature very quickly even if it had not been inside at 70deg immediately prior to the flight.

Pretty much verbatim of what happened to me when my P3 turned off mid flight. I had the batteries in my car and only outside for about 5 minutes. However my outside temp was about 30F (I think around 0C). But still, I considered them warm. However, I'm starting to think the firmware issue could even be triggered when batteries are not very warm.

 

[BigAl07]

Pretty much verbatim of what happened to me when my P3 turned off mid flight. I had the batteries in my car and only outside for about 5 minutes. However my outside temp was about 30F (I think around 0C). But still, I considered them warm. However, I'm starting to think the firmware issue could even be triggered when batteries are not very warm.

While I'm far from a FW guru (I am one of the last to upgrade usually not just with DJI but in almost everything I do... I've been bit on the tail feather by many a FW update lol) I "thought" (key word thought) that the Battery issue was "created" with FW 1.5 and that 1.6 resolved the issue that 1.5 created.

What I will probably do is test a few more "less than full capacity" packs and see how often I can recreate this issue with current FW. Then after some more research I'll upgrade to 1.6 and re-test. I have a few important jobs to get done in the next day or so and I'll test more once those are complete. I'll report back here what I can determine.

 

[alokbhargava]

Great experiment BigAI07, looking forward for similar test with FW1.6.

 

[TheLightSpeedz]

My crash was exactly like the video.... I flew "a little" and had a battery that was at Half. In the cold day after Christmas, I flew again without charging.... It showed 60% on the screen and three bars. The Heathy Drone Analysis said "45%". It was very cold, I warmed up, and did a test flight.... I landed for a second and took off to fly over the neighboring golf course... As I climbed out at full throttle up, it shut off like a light switch.

1.6 changed the thrust for cold weather flying, and I believe today that it was so cold that it resulted in a failure.

DJI replaced my drone free of charge. I lost the battery for good.


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[ianwood]

The key issue is that the P3 power demands are likely exceeding what the battery can provide when it is not in optimal conditions. The motors are demanding more current than the battery can safely provide which is why the voltage sags. This is most likely at full throttle.

 

[Jeff48920]

With the bird and battery on the latest FW, I actually tested this phenomenon indoors with the battery at 35% at takeoff and 68 deg F. Like BigAl I was trying to get the battery down to 8% for recalibration purposes. Immediately after a very slow and controlled liftoff to a height of between 4 and 5 feet:
1. I got the Critical Battery Warning the cell health indicators were red across all four cells
2. The battery percentage stayed at about 30%
3. The Phantom started to become difficult to control
4. I barely landed it when it shut itself off.

I restarted and the battery % indicator showed 35% again. At that point, not willing to test my luck any further, I just let it idle the battery down to 8%. It actually depleted way faster than usual.

 

[CactusJackSlade]

Also keep in mind when a battery gets older you can still have a good % showing but sudden drop in voltage... this is especially true on a battery pack going bad. I have had this happen to 3 of my Phantom 2 batteries. One of them only had 18 total cycles on it when it went bad (unfortunately I was past the warranty period).

In general the P3 batteries seem to be less prone to puffing and going bad. My suspicion is that the P2 (3 cell) batteries were "under rated" and over taxed while flying and possibly one of the reasons that they went to a 4 cell on the P3.... this is just a theory of mine...