Lost Mavic 2 Pro - Battery failure

[mattcoq]

After nearly 150 flights with my Mavic 2 Pro and 400+ in total with my previous drones (P3P & P4P+), I "finally" joined the club of those who lost a drone ...

Nothing fancy and daring, just a classical flight that started well but then started getting a warning at the 56 seconds, with the battery level going from 91% to 0% and "informing" me that the controls of the drone would be from now limited and that immediate landing procedure had started ...

1m34 it was in the water ...

Between the first message (that was beeping up every second until the end), I could only control the rotation of the drone, but in no way go forward, left or right and of course not backwards ...

So, it didn't fall or drop from the sky, but was a "controlled" descent but with very limited possible maneuvers which really frustrated me since from 90 meters to ground or water level, I technically had the time to go from the middle of the canal and land on one of the banks of the canal I was flying above.

All my batteries have been serviced every 20 flights and no pre-warning signs or messages prior to this incident - The battery itself had only 43 charge cycles ...

Here is the airdata link in order to try to understand what happened ...


Clearly possible to see that it is the battery that failed but at the same time, I don't get how such a product can fail when I never had an issue with my P3P and P4P+ (still have the last one that works perfectly)

Also, planning to send some feedback to DJI - Not that I expect anything from then, out of warranty and no DJI fresh, but they should be informed that such an incident occurred with a person who has always taken good care of his equipment ...

Thanks in advance for anyone who will give some feedback on the info provided in the airdata link ...

Matt

 

[slup]

Thanks in advance for anyone who will give some feedback on the info provided in the airdata link ...

Not much to say ... all cells in the battery failed & sank way below 3v where the craft firmware will classify your battery as unsafe to fly with & will force auto land it on the spot.

... I don't get how such a product can fail when I never had an issue with my P3P and P4P+

I'm sorry for your mishap ... but a lot of what you write doesn't add up. LiPo & LiIon batteries aren't static components ... they gets worn every minute all the way from the moment they were manufactured. You can't draw parallels to other batteries & make the conclusion that all other batteries will behave the same.

...All my batteries have been serviced every 20 flights and no pre-warning signs or messages prior to this incident - The battery itself had only 43 charge cycles ...

I'm not following "been serviced every 20 flights" ... what have you done in that service?

Below you have all you need to know in order to care for your batteries, how they respond to use/abuse & age ... & how you can avoid sudden airborne failures.

• Keeping the battery at 100% isn't good for it ... do what you can to minimize the time that they are at that level, the default up to 10 days auto discharge down to 60-65% is way too long ... & if you check the level by pushing the button you reset the counter & the 10 day counter will restart. If a battery that is above storage % level haven't been used in a couple days, use the USB adapter from the Fly More Kit to charge something else (your phone) in order to bring it down to storage % (see below ...)
• Heat kills them ... don't store above room temperature & absolutely not in a car during summer, a couple hours in a burning hot car & the battery have sustained serious damage.
• Let them cool down to room temperature before recharging them.
• Don't fly with a battery colder than 15C degrees, keep them warm in colder weather, have them in a pocket close to your body.
• Store the batteries between 40-60% ... a good thumb rule is to take them of the charger as soon as the third led start to blink, then they are just over 50%. But anything between 1 solid + 1 blinking up to 2 solid + 1 blinking is good enough.
• Don't drain them to low, make sure they don't go under 15% ... once in a while, so be it. Set the ambition to not have them lower than 20% ... if you aim for that you usually don't end up below 15%.
• Don't fly with a battery not recently fully charged, having a battery laying around partially charged for a longer period may make the cells in the battery unbalanced, using a unbalanced battery can make that lower cell fail soon after take off, & initiate a forced low battery auto landing you can’t stop.
• If stored for a long time, cycle them at least once each third month ... then back to storage %.

First of all ... batteries will not last forever

...they will either slowly degrade until the point where the useful flight times are so short that you stop using it


...or it will have a sudden cell failure which will trigger a sudden forced auto landing in the worst possible place


...or it will slowly start to swell to the point where they not fit into the drone anymore


...or the swelling goes off instantly or gets worse when the battery gets hot & push itself out of the drone at height.

The only visual sign is swelling ... which not always occur. Furthermore different drone models have different possibilities to handle a smaller momentary swelling when hot during flight.

So a battery can't be judged only by that it take charge to 100%, isn't swollen & manage to power your drone without mishaps ... too much is going on hidden from just a visual inspection or a test flight, you may have been on the verge to a disaster without knowing it.

You have mainly 2 methods to both prolong the useful service life of the battery & prevent sudden failures ... & judge when it's time to either limit the flight duty (in colder temps for instance) or completely take it off flight tasks.

1.Battery Care
...Never keep the battery cell voltage outside 3,7-3,8v for a longer period than 48h (that is a battery charged to approx 50%). If too high after a flight, discharge them, too low charge them up to storage level again.

...Store them in room temperature ... (too warm is more damaging than too cold)

...Never let them overheat ... (left in the sun or thrown in a hot car)

...Don't charge them hot, let them cool down to room temperature

...Don't use cold batteries, try to have them at room temperature before using them

...Respect the operational ambient temperature specified in the user manual

...Don't push the battery for amp draw (both sticks on max inputs at the same time in Sport mode) when cold or hot ambient temps

...Don't fly them below 15% other in exceptional cases

...Always start a day of flying with the batteries freshly fully charged

2.Battery performance follow up over time
...Follow how the useful calculated max flight time change

...Compare the full charged max mAh compared to the designed mAh

...Monitor how the cell deviations degrades

For all points regarding the battery performance it's a question about trends over time ... just looking at a single flight will not give any insight over the actual health ... having a bit shorter flight time or some bigger cell deviations in one flight can be normal if using Sport mode or flying in colder ambient temps for instance. The paid Airdata subscriptions give the possibility to check these trends over all flight logs uploaded there ... it gives a good decision base to understand the battery health & if it's time to take it off duty.

 

[Kbviper]

I had the exact same thing happen with a Mavic Enterprise Zoom on Nov. 17th, 2019. I took off over water, into a fairly strong wind, and shortly after takeoff started getting messages "Not enough force/ESC Error", and it started going down. I still had directional control, but could not stop the descent. I initially headed towards the breakwater made up of concrete blocks that likely would have severely damaged the drone. Near the end of the flight I had enough altitude to turn towards the sandy beach where it "augered in." No damage, but lots of sand to get out of it.

I have always been careful to properly maintain my batteries and took that one permanently out of service. I never had this problem again and guess that it was a defective battery.

 

[Meta4]

I had the exact same thing happen with a Mavic Enterprise Zoom on Nov. 17th, 2019

Your battery looks sick.
Under the load of the initial climb, cell voltages sank to critical low voltage levels only 19 seconds into the flight.
How long was it before charging the battery and launching?

 

[Kbviper]

Your battery looks sick.
Under the load of the initial climb, cell voltages sank to critical low voltage levels only 19 seconds into the flight.
How long was it before charging the battery and launching?

The battery had been charged up about an hour before the flight. It was about a 1/2 drive to the launch site. The temperature was just above freezing (1.7 C), but the drone/battery was taken out of a warm vehicle and flown about 1 minute later, so it had not cooled down.

I did take off into a fairly strong head wind and was ascending, which put more strain on the battery and may have triggered a failure in a "weak" battery.

I've had a few close calls over the years, but this was the closest I came to losing a drone.

 

[slup]

The battery had been charged up about an hour before the flight. It was about a 1/2 drive to the launch site. The temperature was just above freezing (1.7 C), but the drone/battery was taken out of a warm vehicle and flown about 1 minute later, so it had not cooled down.

I did take off into a fairly strong head wind and was ascending, which put more strain on the battery and may have triggered a failure in a "weak" battery.

I've had a few close calls over the years, but this was the closest I came to losing a drone.

Looks like you have a paid Airdata subscription ... if so, you have access to the trend graphs for your batteries used in the logs you have uploaded there ... how did the battery health look like before this incident, any signs of bad performance that didn't triggered a force landing, kind of close calls?

 

[Meta4]

The battery had been charged up about an hour before the flight. It was about a 1/2 drive to the launch site. The temperature was just above freezing (1.7 C), but the drone/battery was taken out of a warm vehicle and flown about 1 minute later, so it had not cooled down.

That all sounds good, but there are things in the data suggesting it wasn't in good condition.
When new the battery should have had a capacity of 3850 mAh
According to the data, it had a full capacity of 3257 mAh and was at 3131 mAh at launch time.

 

[Kbviper]

Looks like you have a paid Airdata subscription ... if so, you have access to the trend graphs for your batteries used in the logs you have uploaded there ... how did the battery health look like before this incident, any signs of bad performance that didn't triggered a force landing, kind of close calls?

I checked the Airdata logs for the batteries after every flight, looking for cell deviations, and monitor them closely. I have removed batteries from service that showed a lot of cell deviations. I had never noted a problem with this particular battery before, and the log from the flight does not show any cell deviations - bearing in mind that does not mean that the battery is healthy. The flight was normal until about the 23 second mark.

 

[P.J. Pavadore]

I recommend checking for cell balance both before the flight and a few times during the flight. At launch, the cells should be in balance around 4.2 volts (although on my older batteries I average about 4.18) Newer or extremely healthy batteries about 4.3. After launch, voltage dips are normal. On a very healthy battery maybe 4.1 or 4.05, on an older battery maybe 4.0. And any battery that deviates greater than .07 on a single cell is bad.

Another question, how old is the battery?

I'm nearing 2 years on all mine and have begun a refresh cycle to replace them all.