Why did my P3A fall from the sky?

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Hi,

As some of you may have read from my previous posts, my P3A fell from the sky back in September. I believe I fixed it completely except for some cosmetic things. However, I'm getting timid about flying until I learn more about why it crashed in that way. There was no obstacle of any sort, and the battery was almost full. I'm going to upload the flight log in case someone could help me out. Well, the .dat file and .csv files are both too large. Even the zipped version of the .dat file is too large I'll see if I can upload one or both on dropbox or something... Here's the link to the file on dropbox! Dropbox - FLY104.zip

Thanks in advance for your help!
 
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dropbox requires sign in

Mo: So am attaching an Excel file instead, with most of the rows deleted except for the last few hundred.

Here's your previous thread

http://www.phantompilots.com/threads/no-image-transmission-after-p3a-crash.92459

Mo: Thanks for the link!

Possible reasons for crash:

Battery not fully charged

Mo: Battery was at 86% at the time of the crash.

Firmware not updated

Mo: Firmware was current.

Dirty battery connections

Mo: Battery connections appeared to be "clean" but will check again.

Bad battery

Mo: Possible, but how?

Very cold day

Mo: Was a warm day. However, I did have a previous P3A fall from the sky on a very cold day. So I believe a cold day could have brought a P3A down.

good luck...
Mo: Thanks. I converted the log file to an Excel file using dronesmadeeasy.com's converter, and cut out all but the last few hundred lines. They appeared normal to me, but I don't know much about these log files should read. So perhaps someone could help me read it. Thanks!
 

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Hi,

As some of you may have read from my previous posts, my P3A fell from the sky back in September. I believe I fixed it completely except for some cosmetic things. However, I'm getting timid about flying until I learn more about why it crashed in that way. There was no obstacle of any sort, and the battery was almost full. I'm going to upload the flight log in case someone could help me out. Well, the .dat file and .csv files are both too large. Even the zipped version of the .dat file is too large I'll see if I can upload one or both on dropbox or something... Here's the link to the file on dropbox! Dropbox - FLY104.zip

Thanks in advance for your help!
I looked at this .DAT. At about 42 secs the throttle was push all the way forward. Then at 44.6 secs the smart battery system indicated BatteryLimitOutputMax.
upload_2016-10-24_5-59-8.png

Seems unusual, to me at least, that the BatteryLimitOutputMax got triggered in this situation becasue the battery was relatively new and charged to 86%.

At time 62.703 the .DAT abruptly stopped recording. IMHO this was unrelated to the battery warning since there were no other battery warnings such as VoltageLowLand which would typically come next. In addition, the SMART_BATTERY.goHome value never came close to the percentageCapacity which would have triggered a GoHome.
upload_2016-10-24_6-7-55.png


The real issue with this incident is that the .DAT abruptly stopped recording. Possibly the battery wasn't seated properly?
 
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@Mo of Pocatello I was looking some more at this flight and noticed that there was a battery CommError at time -24.2371. This was before the flight which starts at 0.0. This is unusual although I've seen this before. Can't say if it's related to the abrupt stop of the .DAT recording. But, I would be thinking something isn't right about that battery.
upload_2016-10-24_6-34-31.png
 
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That's great information! Where did you get the software for looking at the .DAT file? The output I got from using the online application at dronesmadesimple didn't give useful information. Thanks!
P.S. I clicked on the "DatCon" link and it got me somewhere, so maybe that answers my question. Anyway, thanks!
 
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No, it's not. I won't use a non-OEM battery anymore. I have used non-OEM batteries on other quadcopters with no problems, but I guess I shouldn't use an imitation "smart" battery!


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I converted the DAT file and the issue is all battery related. I believe it started out with the battery being at 87% charge. It appears two of the cells were weak and fell below 3.0 volts which is when the aircraft shuts down and drops from the sky. A fully charged battery would have kept this from happening when it did. Not sure if dji allows any messages before hand to warn you since it was not their battery.
 
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That's great information! Where did you get the software for looking at the .DAT file? The output I got from using the online application at dronesmadesimple didn't give useful information. Thanks!
P.S. I clicked on the "DatCon" link and it got me somewhere, so maybe that answers my question. Anyway, thanks!
CsvView was used for this. CsvView uses DatCon to convert the .DAT to a .csv which is then used to create the graphs shown. CsvView can be obtained by going here.
 
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Thanks to all of you for the very useful information!! I don't think any reasonable battery should have had cells that fall below 3V when the battery as a whole was supposed to be still pretty closed to fully charged. I started out with the battery was fully charged, but had 2 short flights right before this one. With the battery indicator saying that it was 80-something percent full, I thought it was safe to go for another short flight, in fact it should have been safe to go for a fairly long flight!! Anyway, I'm going to learn a lot from this crash, so I guess the crash wasn't wasted in that sense. Luckily the P3A dropped like a rock onto soft sagebrush or something similar. It appears I have repaired it completely except for a dent in the shell and a missing LED cover. Still haven't convinced myself to go through the trouble and expense of replacing the shell. Already have an unused P2 shell that I never used. In fact the P2 seems to need a new central control board because the signal that comes out of one of the channels looks strange. Also, there are so many cables to be reattached that it would take me a long time to figure out!
 
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Thanks to all of you for the very useful information!! I don't think any reasonable battery should have had cells that fall below 3V when the battery as a whole was supposed to be still pretty closed to fully charged. I started out with the battery was fully charged, but had 2 short flights right before this one. With the battery indicator saying that it was 80-something percent full, I thought it was safe to go for another short flight, in fact it should have been safe to go for a fairly long flight!! Anyway, I'm going to learn a lot from this crash, so I guess the crash wasn't wasted in that sense. Luckily the P3A dropped like a rock onto soft sagebrush or something similar. It appears I have repaired it completely except for a dent in the shell and a missing LED cover. Still haven't convinced myself to go through the trouble and expense of replacing the shell. Already have an unused P2 shell that I never used. In fact the P2 seems to need a new central control board because the signal that comes out of one of the channels looks strange. Also, there are so many cables to be reattached that it would take me a long time to figure out!
Are you saying that you don't agree there being a battery issue at all, or?
 
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No, that's not what I meant. I do agree it was a battery issue. I think the non-OEM battery I used was faulty. I also think that any good battery shouldn't have some cells at 3V when the battery as a whole was supposed to be 86% full. I started out with a fully-charged battery, and, after 2 short flights, the battery was at 87%. Under normal circumstances, that should be plenty to start a 3rd flight with. The cells should have discharged evenly, or so I would hope. Unfortunately, two of the cells were under 3V and there was no way for me to know this without analyzing the .dat file.
 
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I thought the Go app has a way to allow you to see the individual cell voltage and the balance...? (I don't use Go)
 
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No, that's not what I meant. I do agree it was a battery issue. I think the non-OEM battery I used was faulty. I also think that any good battery shouldn't have some cells at 3V when the battery as a whole was supposed to be 86% full. I started out with a fully-charged battery, and, after 2 short flights, the battery was at 87%. Under normal circumstances, that should be plenty to start a 3rd flight with. The cells should have discharged evenly, or so I would hope. Unfortunately, two of the cells were under 3V and there was no way for me to know this without analyzing the .dat file.
Looking at the use characteristics of the battery during the flight, it actually looks like the firmware has been setup to put the aircraft in a not-so-good situation, such as what you experienced.

I would not be surprised if you looked at the remaining charge during the flight and thought, looks like I have plenty of juice still remaining. And then out of no where it was down to nothing.
 
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this thread has convinced me buying a genuine spare battery is the way forward despite the temptations on amazon
 
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No, that's not what I meant. I do agree it was a battery issue. I think the non-OEM battery I used was faulty. I also think that any good battery shouldn't have some cells at 3V when the battery as a whole was supposed to be 86% full. I started out with a fully-charged battery, and, after 2 short flights, the battery was at 87%. Under normal circumstances, that should be plenty to start a 3rd flight with. The cells should have discharged evenly, or so I would hope. Unfortunately, two of the cells were under 3V and there was no way for me to know this without analyzing the .dat file.
Also Mo.... Would you mind uploading just the txt file to this flight? There is some things in txt that are not in the dat file that I want to look over. A simple zip the file in a folder and upload it here in this thread.
 

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