175 feet straight down slamming onto a frozen lake!

[The Famous]

Was a very short flight ( 4 minutes) to video some ice fishermen. Using Litchi (as I always do). Was just finishing up when a Battery warning came on! Noted "Battery, Cell #1" can't remember the whole warning. Lost connection at that point. Waited for Return Home as it has always done in the past. Never came back. Went about 100 yards out on the ice and there it was. Upside down. No lights on the battery. I turned the battery on and the craft made the starting sound and one prop moved. How do I check batteries? Any thoughts?

 

[Fly Dawg]

Upload your flight log to this link and post a link to that back here. Airdata does not tell you very much.

DJI Flight Log Viewer

 

[Fly Dawg]

The log will tell you what your cell differential was during the flight, but once power is lost, so is the data, except for the data on the Phantom itself.

 

[dorbot]

Sad story.
Good pictures!
Maybe the battery's ability to provide sufficient current was compromised due to low temperature?

 

[Fly Dawg]

Maybe the battery's ability to provide sufficient current was compromised due to low temperature?

Probably not in this case, since the op stated a Cell#1 error. Usually that indicates a bad battery cell, which will shut down the battery and hence of coarse the aircraft. Wouldn't rule it completely out however.

 

[sar104]

Upload your flight log to this link and post a link to that back here. Airdata does not tell you very much.

DJI Flight Log Viewer

To be fair, AirData tells you just as much as PhantomHelp in the downloadable CSV file, and also has greater in-depth analysis of the power and sensor data than PhantomHelp, but only if you have one of the paid subscriptions.

 

[dorbot]

Yeah, true.
We'll see what the log says if it becomes available.

I think cold may have caused the volts to drop more than usual when under heavy load and the #1 cell warning was just the first one to go. Like you say it could have been a weak cell before, and has just gone unnoticed. Any idea what the charge state was at takeoff?

If any one cell goes below low voltage cutoff then the built in Battery Management System will stop the entire battery? I see it would have to if its a single series design.

I suppose in that case it would be desirable to have internal redundancy with two series sets of cells wired in parallel.
So your range would drop by half if one cell died but at least then it wouldn't drop from the sky. You would have half a chance.......

 

[Fly Dawg]

To be fair, AirData tells you just as much as PhantomHelp in the downloadable CSV file, and also has greater in-depth analysis of the power and sensor data than PhantomHelp, but only if you have one of the paid subscriptions.

Completely correct with the CSV file, I was mainly pointing out that just looking at the online data, you would need a bit more, and agreed on the other points as well. Had I not taken a look at the photo's, I would have never even mentioned the Airdata fact.

 

[dorbot]

I notice there is no evidence of one of the props in the photos.
Again lack of redundancy makes it fall if a prop takes a walk off the map.
Will be interesting to see the conclusion of the investigation!

 

[The Famous]

Having trouble getting into iTunes Connect! Can you try this Airdata file until I figure the darned thing!!

 

[sar104]

Having trouble getting into iTunes Connect! Can you try this Airdata file until I figure the darned thing!!

You have obviously already uploaded the flight log to AirData, so just post the AirData link that will allow us to download the CSV file and, preferably, the original log file.

 

[Fly Dawg]

Quick glance at that file.....Appears to be as stated....Bad Cell#1

Last voltage lines of Cell#1 ( I think)


3.653

3.653

3.653

3.653

3.653

3.653

3.653

3.196

3.196

3.196

3.196

The other cells look normal

 

[Fly Dawg]

Don't count that as completely accurate. That was most difficult to go through. Lets see the actual one.

 

[sar104]

Don't count that as completely accurate. That was most difficult to go through. Lets see the actual one.

Yes - I don't see those values - the final voltage row I see is 3.715, 3.708, 3.666.

And if that pdf is the complete log then it does not appear to contain any clues regarding the event because it just stops with all readings nominal. It's going to require the DAT file.

How to retrieve a V3 .DAT File from the AC

 

[Fly Dawg]

Yes - I don't see those values - the final voltage row I see is 3.715, 3.708, 3.666.

Take a look at page 146 to 153 of that PDF. Far right column should be Cell#1 if I am reading it correctly.

 

[dorbot]

Yup. low voltage cutoff is 3.2v. So you will be pleased to know the chemistry in the bad cell has been protected from undervolting......

What is the timeframe for the above voltages? Why the sudden drop? It looks instantaneous, no curve down atall.
Could it be a measurement error on that cell from the smart battery?

 

[Fly Dawg]

But again, its most difficult to look at it this way.

 

[Fly Dawg]

What is the timeframe for the above voltages? Why the sudden drop?

Lets wait for the real data file. Going through that PDF is a nightmare!

 

[sar104]

Take a look at page 146 to 153 of that PDF. Far right column should be Cell#1 if I am reading it correctly.

Good spot - I missed that. Four cells, not three.

 

[Bakersfield Quad]

I notice there is no evidence of one of the props in the photos.
Again lack of redundancy makes it fall if a prop takes a walk off the map.
Will be interesting to see the conclusion of the investigation!

Good catch