So this evening, I loaded one of my batteries into my Mavic Air,
Battery percentage on DJI go said 85%
I took the drone up about 150 m and flew it out to about 300 m .

Around 3 minutes into the flight I get a warning ,critical low battery voltage and the drone started to initiate landing.(The DJI ladies voice said Landing)
Some kind of disclaimer came up on the screen that I just accepted without getting time to read as I panicked and tried to take control of the drone.

I kept on trying return to home but the drone never responded to it, Fortunately I was able to allow the drone to land in a playing field not far from where I was.

My question is what caused this? And what can I do to prevent this?

Because if the drone was over water where I take it sometimes or even over a road or something it can cause serious accidents or injuries if this happens again

Any explanations or advise?

Always take off with 100% battery just to be safe.
Also check this battery, it might be defective.

Flysafely
Alex

This happened to me 3 times with 1 battery before I sent it in, and by the time I sent it in it was ALMOST too late to get the warranty to cover it. From what I understood there is no fix for it, and DJI did replace the battery eventually. Is it within 6 months of purchase? If not you might be screwed.

Can you confirm for me that the problem was with the battery and not the drone itself? , if it is the battery, I have two others so will just purchase a new one. I had the drone since April 2018 so it's past 6 months, I do however have Dji care but if it's just a battery issue I may just consider purchasing a new battery

SharkExtreme Posted at 1-20 22:38
Can you confirm for me that the problem was with the battery and not the drone itself? , if it is the battery, I have two others so will just purchase a new one. I had the drone since April 2018 so it's past 6 months, I do however have Dji care but if it's just a battery issue I may just consider purchasing a new battery

One of two issues likely.  However best to submit your flight log when this happened and link here for us to examine.  

1. One of the internal cells of the battery has failed and fell to unsafe voltage during flight and triggered a fail safe. If this is the case doing a full dull discharges like discharging the battery by not flying just having the drone turned on and sitting there till it dies then recharging and repeating can sometimes rebalance the cells... but if this doesn’t help then you will need to make a claim with DJI.

Or

2.  your battery may have started self discharge and fell into sleep mode (a weird glitch sometimes occurs).    If battery been unused for 10 days it begins self discharge to protect the cells internally from damaging themselves and sometimes during this period it will also go to sleep and not have a accurate representation of remaining power suggesting 85% whe. It’s realy 5% for example...  this is why you should always fully charge your batteries before flyin or at least charge batteries the day you plan on flying.   The good news about this is it isn’t a defect and you can recover the battery..

Thanks for the response,

I will follow the instructions above and see how it goes.

The log file for the flight can be found here

https://drive.google.com/file/d/ ... -E/view?usp=sharing

My bet it’s the battery and not the drone!

Flysafely
Alex

SharkExtreme Posted at 1-21 10:53
Thanks for the response,

I will follow the instructions above and see how it goes.

unfortunately looks like cell 2 is the problem and not just a small problem its pretty deep, looks like you will have to get this battery replaced.   this isnt just a balance issue as much as it is a damaged cell #2.     
you can if you want, to, do rebalancing.. basically do a dull discharge,  you just leave the aircraft powered on till it dies dont hover it or anything just let it quietly die, recharge and repeat a few times i would repeat this 3-5 times then do a few test flights and see if this issue vanaishes.  give how deeply discahrged cell 2 got during a power run, i doubt this will fix it completely but there is potential just an inbalance issue since it rebounced fairly close to other cell voltages and its starting voltage was mismatched..may not be damaged cell or damaged enough to cause issues if you can rebalance it.

Thanks for taking the time to look at it,

I will dispose of this battery to prevent any further damage or accidents from happening.

SharkExtreme Posted at 1-21 11:43
Thanks for taking the time to look at it,

I will dispose of this battery to prevent any further damage or accidents from happening.

since these batteries are expensive and this maybe recoverable given that cell did rebound and started out a bit weaker.. i would personally do this myself before tossing a battery maybe perfectly good just unbalanced.

to rebalance forcefully: basically do a dull discharge,  you just leave the aircraft powered on till it dies dont hover it or anything just let it quietly die, recharge and repeat a few times i would repeat this 3-5 times then do a few test flights and see if this issue vanishes.  give how deeply discharged cell 2 got during a power run, i doubt this will fix it completely but there is potential just an imbalance issue since it rebounded fairly close to other cell voltages and its starting voltage was mismatched..may not be damaged cell or damaged enough to cause issues if you can rebalance it.

if this doesnt work or keeps falling out of balance, toss it and get another for sure..

HereForTheBeer Posted at 1-21 11:48
since these batteries are expensive and this maybe recoverable given that cell did rebound and started out a bit weaker.. i would personally do this myself before tossing a battery maybe perfectly good just unbalanced.

to rebalance forcefully: basically do a dull discharge,  you just leave the aircraft powered on till it dies dont hover it or anything just let it quietly die, recharge and repeat a few times i would repeat this 3-5 times then do a few test flights and see if this issue vanishes.  give how deeply discharged cell 2 got during a power run, i doubt this will fix it completely but there is potential just an imbalance issue since it renounced fairly close to other cell voltages and its starting voltage was mismatched..may not be damaged cell or damaged enough to cause issues if you can rebalance it.

Thanks for the update.

I will definitely do this and see how it goes.

Can you advise how to check for cell balance and what exactly to look out for?

SharkExtreme Posted at 1-21 11:51
Thanks for the update.

I will definitely do this and see how it goes.

in the dji go 4 app, click on battery icon while in camera viewer to get battery info and it show you cell voltages, and balance graph,

also this which is what i used to pull up your data, but you need to dump log file and upload it to get good view:  https://app.airdata.com

HereForTheBeer Posted at 1-21 11:54
in the dji go 4 app, click on battery icon while in camera viewer to get battery info and it show you cell voltages, and balance graph,

also this which is what i used to pull up your data:  https://app.airdata.com

Thanks... I will try this and let you all know how it goes

SharkExtreme Posted at 1-21 11:55
Thanks... I will try this and let you all know how it goes

sounds like a plan, good luck, hope to hear good things!

Yet another thread where I learned something useful.  Thanks guys!

Skeeter Honey Posted at 1-21 12:24
Yet another thread where I learned something useful.  Thanks guys!

just also decided to check all my batteries tomorrow

HereForTheBeer Posted at 2019-1-21 11:39
unfortunately looks like cell 2 is the problem and not just a small problem its pretty deep, looks like you will have to get this battery replaced.   this isnt just a balance issue as much as it is a damaged cell #2.     
you can if you want, to, do rebalancing.. basically do a dull discharge,  you just leave the aircraft powered on till it dies dont hover it or anything just let it quietly die, recharge and repeat a few times i would repeat this 3-5 times then do a few test flights and see if this issue vanaishes.  give how deeply discahrged cell 2 got during a power run, i doubt this will fix it completely but there is potential just an inbalance issue since it rebounced fairly close to other cell voltages and its starting voltage was mismatched..may not be damaged cell or damaged enough to cause issues if you can rebalance it.

Hi hereforthebeer

Old thread but you seem so helpful... I had my mavic air fall out of the sky today because the app was giving me indications that I had plenty of battery when I obviously didn't.  Where do I get the flight log ?  I am suspecting it is a bad battery since it was my footrest flight since last fall and the battery said it was charged but may not have been?  Thanks so much.

djiuser_49xwwHG8rmoc Posted at 5-15 17:57
Hi hereforthebeer

Old thread but you seem so helpful... I had my mavic air fall out of the sky today because the app was giving me indications that I had plenty of battery when I obviously didn't.  Where do I get the flight log ?  I am suspecting it is a bad battery since it was my footrest flight since last fall and the battery said it was charged but may not have been?  Thanks so much.

i havent extracted logs in a good while but im sure instructions on this forum how to do it for IoS and Android.  

dji batteries self discharge when they are left to rest for more then a few days usually about 10 days by default ..  so question is did you attempt to recharge the battery packs before going out?   did you do a hover test to make sure batteries are till healthy before a actual flight over open terrain?    for any high power density battery like Lithium -ion/poly battery been sitting a while you should always store them between 30% and 50% charge or there about if not going to use them for a good while, also shouldn't just fly a battery right after storage, should charge it up first or cycle it once (charge and discharge it using hover in place method), ideally.  

sadly, i doubt much of a case here for DJi to help you with as it is in instructions how to care for batteries and likely come down to user error... my guess is either self discharge system mostly deleted your battery and somehow forgot how much compacity it drained so suggested a full battery when it was actually weak or the battery was damaged and self discharge system for some reason failed to do its job.. in this case, maybe some remote possibility for dji to cover both drone and battery but 99% unlikely they will because proving that specifically occurred is nearly impossible, battery drain issues almost always look the same.