90% to Critically Low in 5 seconds....

[Mithrandir]

Good day.
My 2 year old Mavic Air, prolly 100 flights, did something this weekend it never did before.
In fact, it has been 100 percent reliable and trustworthy!
I took off with 93% battery... flew for about 1 and a half minutes and suddenly it goes into
emergency land mode. Started flashing a Critically Low Battery warning.

It did this with 3 different batteries.

Even tired old batteries do not suddenly and catastrophically die in less than 5 seconds....

They may degrade quickly... but not suddenly.

I have seen in other forums this problem happens... but no actual reason is discovered....

Has anyone else actually solved this riddle!?!?

thanks

 

[zeusfl]

How long you had without flying the drone?
Did you passed any long period without charge the batteries? Where the batteries for long time in 0% charge?

 

[Recoveryone]

Normally, it would be a bad battery cell,, but for it to happen to 3 different ones I would suggest checking the prong connectors on the drone. If the batteries are not fitting correctly may be the cause for the rapid discharge.

 

[Mithrandir]

I flew the battHow long you had without flying the drone?
Did you passed any long period without charge the batteries? Where the batteries for long time in 0% charge?

I flew the drone about a week before... I always verify 4 LEDs on the battery before I even insert the battery into the drone..

The batteries did not rapidly discharge... they would be rather hot if they drained that quick...

 

[zeusfl]

I will say, to try to update all batteries firmware with the DJI assistant 2 for Mavic application. There is a chance, the aircraft firmware has been updated and the batteries firmware has not been updated.

When the Li-Po came age, they tend to hold less and less charge. There is a point that take for ever to charge and only hold few milliamps before are discharged.

 

[Tufargon]

That's a common thing for a lot of drones with smart batteries when you try to fly with a battery that was charged a couple days or more before flying. They are set to discharge as they sit to protect them and when you plug them into the drone you might get a higher % on screen than they actually are. It's happened to me with 2 consecutive batteries one day when I had charged them a few days earlier. I now ALWAYS recharge/top them off within 24 hours of flight.

 

[Mithrandir]

That's a common thing for a lot of drones with smart batteries when you try to fly with a battery that was charged a couple days or more before flying. They are set to discharge as they sit to protect them and when you plug them into the drone you might get a higher % on screen than they actually are. It's happened to me with 2 consecutive batteries one day when I had charged them a few days earlier. I now ALWAYS recharge/top them off within 24 hours of flight.

my batteries were charged a day or two prior to flying.... they are set to begin discharge by default after 10 days of sitting....

I fly large RC electric planes, (10S x 5000 mah 3 kw) so I have 15 years+ of living with LiPo batteries.
LiPos can become extremely pathetic and not have such a drastic loss of voltage.
I do suspect this is either an issue with the hardware inside the battery, all 3 batteries doing the same thing at the same time isn't consistent with that, or software... I have never updated any battery software.
I flew again today... no problem....
Previous experience with this sort of issue, if I don't find a reason, I can never trust it again!

 

[Meta4]

Has anyone else actually solved this riddle!?!?

The obvious first step to solve the mystery is to look at the recorded flight data which will probably show what was going on.

 

[slup]

...prolly 100 flights, did something this weekend it never did before.

...suddenly it goes into emergency land mode.

...They may degrade quickly... but not suddenly

...no actual reason is discovered....anyone else actually solved this riddle!?!?

Yeah ... but eventually the battery will fail, they don't last forever. If you haven't followed the degradation regarding cell voltage drops, cell deviations, average useful flight times & how they perform in hot/cold environment over time, this will always come as a surprise.

So when you say it came suddenly... you probably don't know, perhaps this have nearly happen before in several flights without you knowing it.

And this is usually not a riddle ... all DJI models will go into autolanding as soon as one cell goes under 3V.

Why a cell goes that low is usually a combination of:
-Old batteries (1-2 years old)
-Batteries with a high charge cycle count
-Have been unused for a longer time
-Not being stored at the correct voltage level (30-60 percentage wise or 3,7-3,8V/cell)
-Cells have self discharged so cells gone out of balance due to laying around partially charged then never got a full charge before flight
-Have been left well over 48h on 100% ... or lower then 15%.
-Have been overheated

All what happened during the flights with those 3 batteries have been recorded in the flight logs ... go here & read up on how to retrieve the mobile device .TXT logs for the 3 flights --> Mavic Flight Log Retrieval and Analysis Guide (read under section 3.) then attach them in a new post here & we can read out what caused the autolanding to kick in.

 

[DanMan32]

The default days to discharge used to default to 10 days, but DJI changed it last year at least for the M2 to 5 days. I believe that was also done for the MA1.
If you fly just when the discharge cycle starts, it may show high charge state but discharge circuit still engaged. That could cause issues. Topping off charge will turn off the discharge circuit.

There is circuitry in these batteries that get updates from time to time along with an AC firmware update. One can refresh the AC firmware with Assistant, but no way to directly refresh the battery firmware. Battery firmware gets passed on from the AC.

When flight ended showing 5%, did the battery LED also show this?

 

[Tufargon]

my batteries were charged a day or two prior to flying.... they are set to begin discharge by default after 10 days of sitting....

I fly large RC electric planes, (10S x 5000 mah 3 kw) so I have 15 years+ of living with LiPo batteries.
LiPos can become extremely pathetic and not have such a drastic loss of voltage.
I do suspect this is either an issue with the hardware inside the battery, all 3 batteries doing the same thing at the same time isn't consistent with that, or software... I have never updated any battery software.
I flew again today... no problem....
Previous experience with this sort of issue, if I don't find a reason, I can never trust it again!

I was in no way trying to insinuate that you didn't know your stuff. You asked and I gave you my experience (as well as probably 50 or more others who experienced the same). That never happened again, even with the same two batteries after I started charging them within 24 hours of flight. You flew all 3 the next day and it didn't happen so that leads me to believe even more that it was the issue. Other posts basically say the same.
Also saying "all 3 batteries doing the same thing at the same time isn't consistent with that, or software...". It is absolutely consistent with that if they were all charged at the same time and flown the same day. It's easy to test. Charge them up and wait 3-4 days and try hovering there for a while and see if it happens again. Many of us have tested this in another forum and it turned out to be true. So we told the manufacturer who then recommended recharging/topping them up before every flight.
Hope you find the issue.

 

[mmlaverman]

Mithrandir, I had the same exact situation happen to me including the time it took to go down to critically low battery on Sunday. My batteries have a little less use then yours and I keep them in top condition. Currently, my research has found that a battery firmware was missed being updated (which was mention above) and I'm waiting for DJI to confirm as I presented them with my flight information and update history.​

​

My Mavic Air missed a tree branch by inches coming down but I think my heart rate is still up over what happened!​

 

[Meta4]

I'm waiting for DJI to confirm as I presented them with my flight information and update history.

​

If you post flight data here you'd get an independent analysis a lot faster.

 

[boblui]

I took off with 93% battery... flew for about 1 and a half minutes and .... Critically Low Battery..

It did this with 3 different batteries.

That's really weird ..... If it happened on 3 batteries, it is highly unlikely to be due to bad cells or problems with the BMS - the small computer inside the battery for monitoring things going on inside. The common point is the drone but I cannot imagine what could go wrong to cause this. May be for some reasons it draws a lot of current ? Posting the flight log will help to gain some insight into the issue.

 

[DanMan32]

That's really weird ..... If it happened on 3 batteries, it is highly unlikely to be due to bad cells or problems with the BMS - the small computer inside the battery for monitoring things going on inside. The common point is the drone but I cannot imagine what could go wrong to cause this. May be for some reasons it draws a lot of current ? Posting the flight log will help to gain some insight into the issue.

Not weird at all.
He changed all three batteries at the same time.
Days later, just when the discharge cycle started, he flew with all three batteries.
All three batteries show 93% because discharge cycle had just started.
The design of the batteries and how they self discharge tend to cause cell deviation when flown while self-discharging.
This causes rapid loss or apparent loss of power. I add apparent because battery may still have quite a bit of energy, just not balanced and/or not accurately measured.

So the common element is that all three batteries were treated the same way at the same time.

 

[boblui]

Not weird at all.... All three batteries show 93% because discharge cycle had just started....

I often started flying with far less than 93% battery and never had encountered the battery dropping to the critical level ( around 11% ) in less than two minutes. Self discharging is very slow and should not cause any rapid loss of power, be it real or apparent.

 

[Meta4]

Until there's some hard data to look at, it's pointless arguing about what might/might not have cause the issue.

 

[slup]

Can't agree more, we can't say anything more about the OP's incident without logs ... but sure, common battery knowledge is still a very valid subject to discuss while waiting

The default days to discharge used to default to 10 days, but DJI changed it last year at least for the M2 to 5 days. I believe that was also done for the MA1...

Unfortunately that's not true ... for the MA1 it's still 10 days & if you push the battery button to check them the 10 day counter resets.

...You flew all 3 the next day and it didn't happen...

Well ... how can you be sure without looking into the logs. Even though a forced autolanding wasn't triggered it may have been close ... without checking the performance of the cells it's impossible to know if the cells suffered from voltage sag even the second time.
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All of my 3 MA1 batteries that came with the Fly More kit (manufacturing date Jan 2019) have degraded very similar so far. If I hadn't followed them up regarding performance trends I would say that they are as good as new ... they still give me around 14-15min flight time & aren't swollen.

But looking into the cell deviations & voltage sag under load ... all over time (trend) show another story ...

This is from the worst of the 3 ...

Here below from the cell deviation trend from all my flights with it ... it shows that major cell deviations happens more & more often in the flights (purple bars), especially when it's colder weather ... this in parallel with major voltage sags.



And here the voltage sag from the individual flight that made me taking it out of flight duty ... I was very near a forced autolanding there, & it was over water there so it had been fatal.



And here in a later "try out" flight well prepared for a forced auto landing ... it didn't occur to the same degree at all this time.



This battery is now doing desk duties & at maximum near flights where I can handle a autolanding ... The other 2 batteries from the combo isn't far behind ... but still trusted for flight duty but closely monitored.

 

[Icelandman]

Good day.
My 2 year old Mavic Air, prolly 100 flights, did something this weekend it never did before.
In fact, it has been 100 percent reliable and trustworthy!
I took off with 93% battery... flew for about 1 and a half minutes and suddenly it goes into
emergency land mode. Started flashing a Critically Low Battery warning.

It did this with 3 different batteries.

Even tired old batteries do not suddenly and catastrophically die in less than 5 seconds....

They may degrade quickly... but not suddenly.

I have seen in other forums this problem happens... but no actual reason is discovered....

Has anyone else actually solved this riddle!?!?

thanks

Lucky you for flying 1 and a half minutes. All my 3 batteries did the same but in about 20 seconds from 99% full to critically low. I have written to DJI 3 times and haven't had the courtesy of a reply or acknowledgement of my enquiry. Pretty disappointed as they had only been charged about 30 times each. Cannot find a reason either.

 

[Tufargon]

Well ... how can you be sure without looking into the logs. Even though a forced autolanding wasn't triggered it may have been close ... without checking the performance of the cells it's impossible to know if the cells suffered from voltage sag even the second time.
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I wasn't saying the cells weren't damaged. My point was that he charged them up and flew the next day without the drop. I've seen this 50 times or more and went through it myself. A google search on DJI sudden battery drop will show a lot of results. A recharge/top up within 24 hours of flight usually fixes this. Could be a new battery won't do this and one that has more cycles will but either way I top them off EVERY time now. It can be a scary situation when this happens. I near peed myself lol.

Edit: One of my 2 batteries did need to be returned and the other was fine but it happened on both that day. Both were charged at the same time about 5 days earlier.
As I posted earlier in the thread. It's easy to test.