Mavic 2 - Battery 63% -> 0% instantly. Voltage Drop. HELP!

[gershee]

DJI Mavic 2. Battery is in good health. No swelling. Was not hot or cold. Maybe 40 cycles.

I took off with 63% battery (I usually only take off with full batteries but the plan was one quick video about 400ft away.)

Drone gets about 400ft away. About 120ft altitude and battery goes immiedetly to 0. Voltage drop warning. Begins forced landing. I'm over a lake and fly straight for land but don't make it. Drone goes in the water. Sinks.
What happened?
Will DJI cover this battery malfunction?
Drone is over 1 year old. This battery was bought separate and is probably about 13months old.
The flight location is a lake thats water level fluctuates so what the map says/shows as land wasn't necessarily land. I chose the shortest route to land once the quad began to drop.

Flight record:

DJIFlightRecord_2020-06-29_[09-44-22].txt

drive.google.com

DAT:

20-06-29-09-43-33_FLY083.DAT

drive.google.com

Flight Log Viewer:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

 

[fGene]

I can't view the log but the symptoms indicate a short circuit.

 

[gershee]

I can't view the log but the symptoms indicate a short circuit.

Can you try now? Links should be fixed.

 

[sar104]

DJI Mavic 2. Battery is in good health. No swelling. Was not hot or cold. Maybe 40 cycles.

I took off with 63% battery (I usually only take off with full batteries but the plan was one quick video about 400ft away.)

Drone gets about 400ft away. About 120ft altitude and battery goes immiedetly to 0. Voltage drop warning. Begins forced landing. I'm over a lake and fly straight for land but don't make it. Drone goes in the water. Sinks.
What happened?
Will DJI cover this battery malfunction?
Drone is over 1 year old. This battery was bought separate and is probably about 13months old.
The flight location is a lake thats water level fluctuates so what the map says/shows as land wasn't necessarily land. I chose the shortest route to land once the quad began to drop.

Flight record:

DJIFlightRecord_2020-06-29_[09-44-22].txt

drive.google.com

DAT:

20-06-29-09-43-33_FLY083.DAT

drive.google.com

Flight Log Viewer:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

You know what the problem was - you launched with a partially discharged battery so the cells were out of balance. Cell #1 collapsed soon after takeoff:



It doesn't seem to matter how often it is pointed out that flying with discharged batteries is incredibly risky for exactly this reason - it just keeps happening.

You may as well ask DJI if they will cover it but with a battery in that condition the most likely response is user error.

 

[Meta4]

DJI Mavic 2. Battery is in good health. No swelling. Was not hot or cold. Maybe 40 cycles.

Same issue as this one:

Critically Low Voltage Error - Forced Landing

Hi there This is my first post so please excuse if i dont follow the norms. I have a Mavic Pro. I put it in the air over the weekend and for the first time had a Critically Low Power/Voltage error displayed and it automatically started to land my drone. The following morning i put the drone up...

mavicpilots.com

 

[PhantomFandom]

I took off with 63% battery

That's all I really needed to read. NEVER launch with less than a 100% battery. Launching with a partially discharged battery is bad news.

Drone is over 1 year old and battery is over 6 months old so even if it was a true malfunction, I don't think DJI would have offered anything other than perhaps a discount on a new purchase.

Being that this was not a malfunction but rather pilot error, then there really is nothing to be done other than calling it a learning experience.

 

[supermarcie]

How does it come that a cell goes out of balance? is this because of the self discharge?
When I first charge to 100% will a cell then never goes out of balance while flying?

 

[sar104]

How does it come that a cell goes out of balance? is this because of the self discharge?
When I first charge to 100% will a cell then never goes out of balance while flying?

Correct - the self-discharge process doesn't keep the cells balanced.

 

[gershee]

I flew the battery a few hours before and it was 100%. It never self discharged.

 

[sar104]

I flew the battery a few hours before and it was 100%. It never self discharged.

Then it's a faulty battery.

 

[Meta4]

I flew the battery a few hours before and it was 100%. It never self discharged.

The voltage per cell is the important measure while the % indicator is just a handy approximation (if you start with a fully charged battery).
Your battery was down to critical low voltage (<3.3V) within 20 seconds of launching.

 

[rfc]

The voltage per cell is the important measure while the % indicator is just a handy approximation (if you start with a fully charged battery).
Your battery was down to critical low voltage (<3.3V) within 20 seconds of launching.

If one adds checking the relative voltage level of the cells to their pre-takeoff check list, what guidance is there as to how far off once cell should be for a "go-no go" decision? I know it's always preferable to fly with fully charged batteries, but sometimes can't do so.

 

[slup]

If one adds checking the relative voltage level of the cells to their pre-takeoff check list, what guidance is there as to how far off once cell should be for a "go-no go" decision? I know it's always preferable to fly with fully charged batteries, but sometimes can't do so.

You have some guidance from Airdata.com's values below in the pics ... but honestly, you should avoid flying with a battery partially depleted, the only exception I see is if you start out with 100%, flying it down partially & change for a full one for a longer flight and then return to the partially depleted one to fly it down ... all in the same flight session.

But drone batteries will not last forever ... sooner or later they will fail & surprise you with a forced autolanding. The only way to see that coming & ground the battery in time is to monitor the trend, especially regarding cell deviation.

In general, cell deviations is normal and occur to a degree in every flight. The deviation can be used as kind of a health indicator beside possible maximum flight times for a battery which also degrades over time & use. As minor deviations is normal, major ones if repeated regularly in several flights instead can be a sign of a more alarming battery degradation & if to severe over multiple flights that battery perhaps need to be taken off flight duty before a cell fails with immediate auto landing as a consequence.

With a paid subscription for Airdata.com you can study the battery behavior over all the flights you have uploaded there ... if we start to check one single flight that I did yesterday. It was with my worst battery, in approx 20C degrees, used P-mode & flew constantly with full elevator & without to many height changes. All this equals to a moderate stress load on the battery.

In here Airdata also gives some explanations regarding deviations in general ... it shows minor deviations coming from cell 3, but still in yellow area, not alarming alone.



And here a bit more detailed throughout that single flight ... (the green bars more then 0,01V is what makes above gauge go to yellow)



From this single flight it's hard to tell if something is alarming ... besides that the battery constantly suffer from minor cell deviations of approx. 0,02V ... & that I know that my other 3 batteries have less minor deviations than this.


But if we look at the trend for this battery ... compiled from all the flights I've used this battery the picture becomes different, also here Airdata gives some explanations ... The pop-up window upper right and the last bar to the farthest right is the single flight above ...



Here we see major sized deviations from that battery in other flights ... I know that those purple bars occurred when I either was flying in temps below freezing or/and extensively used Sport mode. This performance I don't see from my other batteries. So ... I monitor this battery & try to avoid hard flying and/or cold weather with it, so far I'm not afraid to use it.

 

[supermarcie]

very nice information on airdata.com!
But costs a lot of money if you want all information.
But if you also get notifications of bad batteries then you can avoid a crash because of that!

 

[supermarcie]

Another question, when I check all my flights the battery deviation is always in cell 3
And this for all my batteries (3), is there a reason why it is always in Cell 3?

 

[TerryToast]

Correct - the self-discharge process doesn't keep the cells balanced.

The self discharge sounds seriously flawed. If it can’t discharge and keep the cells balanced, then it should discharge right down to 10-20% so uneducated users (like myself) don’t try to fly with an potentially unbalanced (60%) battery.

 

[Meta4]

so uneducated users (like myself) don’t try to fly with an potentially unbalanced (60%) battery.

Balanced or not, you shouldn't be launching with a battery that's discharged to 60%.
The cells in your battery were down to critical low voltage after 20 seconds of flight, before the cell balance was significant.

 

[sar104]

The self discharge sounds seriously flawed. If it can’t discharge and keep the cells balanced, then it should discharge right down to 10-20% so uneducated users (like myself) don’t try to fly with an potentially unbalanced (60%) battery.

I think that DJI might simply have hoped that users would follow the instructions. Asking a lot, I realize.

 

[TerryToast]

I think that DJI might simply have hoped that users would follow the instructions. Asking a lot, I realize.

OPTION A: Users should read the instructions and not fly after automatic discharge to 60%

OPTION B: DJI can program the drone/battery to discharge to 10-20%.

I wonder which of these two options would be a lot more successful and user friendly? ?

 

[slup]

OPTION A: Users should read the instructions and not fly after automatic discharge to 60%

OPTION B: DJI can program the drone/battery to discharge to 10-20%.

I wonder which of these two options would be a lot more successful and user friendly? ?

Yep ... still option A.

With your invented option B we would see floods of battery fails ... this as 10-20% is a damaging storage level. May I suggest Googling a bit about LiPo batteries, it's a lot to learn about them too.