If your Mavic falls out of the sky...

[Callum]

The other thing I forgot to mention is that the power cables are pretty stout and are likely under a bit of spring tension.
So if it lets go it would be very sudden and final - no stuttering as the wires bounced..

That would explain the transfer of energy from casing to the soldered joint as mavic hit the ground.

I do agree that in the photo it definitely looks like a poor soldered joint but we can't underestimate the forces acting on the mavic when dropped from height to a sudden stop.

 

[StrayaMavic]

Your'e paying 2x more than your need to.,...just like a real airline. LOLOLOL

We call that the Australia Tax actually

 

[Brojon]

That would explain the transfer of energy from casing to the soldered joint as mavic hit the ground.

I do agree that in the photo it definitely looks like a poor soldered joint but we can't underestimate the forces acting on the mavic when dropped from height to a sudden stop.

It acts like a spring - it would be logical to assume the wires would actually mitigate some of the flex from impact. Plus I'd add that the entire assembly is cushioned with dense foam strips - the battery pack isn't just flopping around.

 

[f3honda4me]

Some guy from Germany just posted one where he was apparently landing and ... boom.
The data file doesn't show anything definitive - just an abrupt end about 30 meters off the ground.

Let's be careful though. There are a lot of things that can cause this. Battery disconnecting a wire is one of them, and we don't even know how often that actually has occurred. Plus a drone going through a slow and gentle landing operation isn't exactly something I'd expect to have enough force to pop the connection loose.

 

[Brojon]

Let's be careful though. There are a lot of things that can cause this. Battery disconnecting a wire is one of them, and we don't even know how often that actually has occurred. Plus a drone going through a slow and gentle landing operation isn't exactly something I'd expect to have enough force to pop the connection loose.

He was flying in Sport mode. That tends to run 'em a little hotter.
But yeah - who knows? But it would explain a lot of the mysterious falling out the sky issues if this is an ongoing quality issue.

 

[f3honda4me]

He was flying in Sport mode. That tends to run 'em a little hotter.
But yeah - who knows? But it would explain a lot of the mysterious falling out the sky issues if this is an ongoing quality issue.

I can only recall one recent falling out of the sky issue that was not explainable. If there are more someplace I haven't seen I'd like to see?

 

[Brojon]

I can only recall one recent falling out of the sky issue that was not explainable. If there are more someplace I haven't seen I'd like to see?

By explain do you mean blaming the operator and claiming they didn't seat the battery properly?
I'm not advocating this is the uber cause, just that it's a possibility. You may choose your own beliefs.

 

[f3honda4me]

By explain do you mean blaming the operator and claiming they didn't seat the battery properly?
I'm not advocating this is the uber cause, just that it's a possibility. You may choose your own beliefs.

Battery coming unseated can actually be seen in the drone's DAT file. So could your wire disconnect for that matter. The difference being the battery would not work after the wire becoming disconnected in most cases.

 

[Brojon]

How does the log file show a battery coming unseated?

 

[sar104]

How does the log file show a battery coming unseated?

The resulting voltage drop takes place over several tenths of a second, and is recorded in the log before the voltage drops too low for the FC to continue functioning.

 

[Callum]

It acts like a spring - it would be logical to assume the wires would actually mitigate some of the flex from impact. Plus I'd add that the entire assembly is cushioned with dense foam strips - the battery pack isn't just flopping around.

Even foam strips allow some travel. The case stops instantly and internals continue to travel until energy is absorbed by the foam. If there are separate parts they can decelerate at different rates causing shear forces on any linkages.

I do think your on to something though and there may be an issue here. The joint should never have separated the way it did.

 

[Smecky]

Do we need to start opening our batteries and glueing the terminal. Or do dji need to do a recall like Car company’s do????

 

[Brojon]

The resulting voltage drop takes place over several tenths of a second, and is recorded in the log before the voltage drops too low for the FC to continue functioning.

Given that the motors are drawing amps of current and there are no large capacitors to act as storage I'd have to put on my Missouri t-shirt and say "show me". I can see interruptions for maybe milliseconds but not 10ths of seconds - the Mavic draws a heap of juice to run.
Now if the battery has some momentary contact issues as it works its way loose, I can maybe see that getting recorded - but not a popping out. In my mind I've always assumed a poor seating would show up as a series of events as the battery and the contacts are jiggled. The battery is responsible for on/off power so if it gets a bounce and comes loose it will cause the Mavic to lose power, then it reconnects and et voilá - we have power. I'm not sure how that messes with the internal state of the bird though.
I think I see an experiment coming.

 

[Brojon]

Do we need to start opening our batteries and glueing the terminal. Or do dji need to do a recall like Car company’s do????

I'm just making DJI aware of what I found - only they can determine the extent of the issue - if any. I may have just gotten the 1 in a million.
With the exception of those ginormous solder blobs on a power connector I'm pretty impressed with DJI quality overall.
A cold solder joint is bad on many levels and I would hope they have a quality check on them. I programmed an assembly machine once to look at cold solder joints at an inspection station - our best measure was to train a light on them and check the specularity. A cold joint scatters the light more than a good joint. Between that and a resistance test it was pretty good at finding them. That was many many moons ago - they have much better stuff these days.

 

[Callum]

Do we need to start opening our batteries and glueing the terminal. Or do dji need to do a recall like Car company’s do????

There's only been one proven case of this type of failure and that was after a crash.

Problem is it's sealed inside battery and most people wouldn't bother to check.

Unless we have more people cracking open a battery after this type of crash we just won't know and rely on DJI for transparency.

DJI may well be aware of it after inspecting returns or on the other hand it may be an isolated case.

Brojon has made DJI aware of the issue so it's up to them to investigate.

 

[sar104]

Given that the motors are drawing amps of current and there are no large capacitors to act as storage I'd have to put on my Missouri t-shirt and say "show me". I can see interruptions for maybe milliseconds but not 10ths of seconds - the Mavic draws a heap of juice to run.
Now if the battery has some momentary contact issues as it works its way loose, I can maybe see that getting recorded - but not a popping out. In my mind I've always assumed a poor seating would show up as a series of events as the battery and the contacts are jiggled. The battery is responsible for on/off power so if it gets a bounce and comes loose it will cause the Mavic to lose power, then it reconnects and et voilá - we have power. I'm not sure how that messes with the internal state of the bird though.
I think I see an experiment coming.

There have been two examples analysed recently that clearly show the voltage start to sag and then the record ends at around 7 V, and where permanent battery disconnection was confirmed. The motor voltage is recorded at 50 Hz and the drop occurred over several data points so it probably was of the order of tens of milliseconds. I'll try to dig out one of the files, or @BudWalker may be able to find one faster - he has better organized records than I do. It's also an easy event to replicate by dislodging the battery of a powered-up aircraft of course, although I haven't done that.

 

[BIGDAVE]

will check both of my batteries, the the cells seem to be with in spec. only .01 difference.

OK I'm just wondering on how you check each cell for voltage? I'm not having any problems other than signal loss but I think this may be important to check out every once in a while. thanks

 

[BudWalker]

There have been two examples analysed recently that clearly show the voltage start to sag and then the record ends at around 7 V, and where permanent battery disconnection was confirmed. The motor voltage is recorded at 50 Hz and the drop occurred over several data points so it probably was of the order of tens of milliseconds. I'll try to dig out one of the files, or @BudWalker may be able to find one faster - he has better organized records than I do. It's also an easy event to replicate by dislodging the battery of a powered-up aircraft of course, although I haven't done that.

here's one
Wierd Crash...what happened and what to do?
@Brojon

 

[sar104]

here's one
Wierd Crash...what happened and what to do?
@Brojon

And another:

Mavic Pro dropped out of the sky

 

[locoman]

GO4 app, ..., battery, must be connected to MP.