Battery from 94% to 0% Forced Landing (with flight log)

MavicG · Feb 8, 2021

I had 100% charged 3 batteries last night and flew fine with 2 batteries. When I put the 3rd battery in it was at 98% and I flew for about 2 minutes and got forced landing message and battery indicator said 0%. Luckily I was able to land on the side of the road. A really scary situation as I was flying over water. Mavic 2 Pro is 1 year old. Weather condition today 30 degrees Fahrenheit and batteries were kept warm in my car prior to flight and again charged fully last night. Help to find out what happened would be greatly appreciated.

Here's the log file ...

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

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MavicG

iamcostas · Feb 8, 2021

Sudden Disconnection without RTH - Can anyone tell me what happened?

I flew to capture a ferry passing at breaker bay then sudden disconnection from RC & no RTH - was allgood then gone Now I have no drone Can someone analyze my flight & tell me what happened

mavicpilots.com

Maybe similar...

iamcostas · Feb 8, 2021

After reading this, if I had Mavic 2 pro, I would not dare to fly it above water until there is some kind of logic explanation... or maybe not fly it at all.

iamcostas · Feb 8, 2021

battery Problems Mavic 2 Pro

I have a Mavic 2 Pro and just recently went to fly it with fully charged battery and got up to 50 metre and the message came up "Critically low battery- Land immediately". So I did. Recharged the battery and the same thing happened. Yesterday I was flying using another fully charged battery...

mavicpilots.com

Phantomrain.org · Feb 8, 2021

Welcome to the Mavic 2 Family

One thing you can do is check your firmware on each battery and make sure they are all running the same update.

Phantomrain.org
Gear to fly your Mavic 2 in the Rain / and land on Water.

Thomas B · Feb 8, 2021

MavicG said:
I had 100% charged 3 batteries last night and flew fine with 2 batteries. When I put the 3rd battery in it was at 98% and I flew for about 2 minutes and got forced landing message and battery indicator said 0%. Luckily I was able to land on the side of the road. A really scary situation as I was flying over water. Mavic 2 Pro is 1 year old. Weather condition today 30 degrees Fahrenheit and batteries were kept warm in my car prior to flight and again charged fully last night. Help to find out what happened would be greatly appreciated.

Here's the log file ...

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

MavicG

Check for swelling on the bottom of the battery. I had one go bad in flight in about 70-90 secs and barely got back home. Went from 99% to below10% instantly. Any swelling (convexity, bulging) is the sign of a bad battery.

bumper · Feb 8, 2021

On my M2P w/Smart Controller a tap on the battery symbol, on the screen upper right, displays individual cell voltage. There have been occasions when I've needed to fly unplanned for a few minutes with a battery at storage voltage. No problems, nor would I expect there to be - - but from now on I'll be sure to look at individual cell voltage first.

boblui · Feb 8, 2021

The voltage started dropping very quickly after takeoff reaching a minimum cell voltage of 2.5 ~ 3.3 V which were abnormally low as 0% battery corresponds to a cell voltage of 3.58V on my M2P. The low voltage made the BMS ( Battery Management System, the small computer insider the battery ) believe that the battery was depleted so it changed the battery % figure to zero. This has been seen in some recent cases but the craft involved was Air 1.

As soon as the craft stopped ascending and the loads on the motors reduced, the cell voltage rised quickly back to a very healthy level of 3.8V so you were able to land the craft safely.

When the craft was ascending, there were a lot of "Not Enough Force/ESC Error" warnings indicating that the motors were under high load. It is likely that the consequent high current drawn from the battery caused the cell voltage to drop. Unfortunately the log does not contain any info on current so it is not sure if the current was really too large or the battery's internal resistance was abnormally high. May be you can try another battery. If the same phenomenon is seen, there may be some problem in the power system of the craft. Before doing so I would suggest you to update the firmware and GO APP to the latest version so that more info can be seen in the flight log.

slup · Feb 9, 2021

MavicG said:
... Mavic 2 Pro is 1 year old. Weather condition today 30 degrees Fahrenheit and batteries were kept warm

Thing's like this will always happen eventually ... LiPo batteries don't last forever. All battery wear accumulate gradually & the result suddenly show up during a flight where the battery is put under stress in a, for a battery, unfriendly environment.

All gradual deterioration is mainly invisible if not monitoring the performance trends over time regarding voltage drops, cell deviations, possible maximum flight times, charge cycles & remaining full mAh compered to designed capacity. Furthermore all these deteriorating factors can be speed up by not treating the battery correctly during storage & usage.

Colder weather, which leads to lower operating temps & higher internal resistance for the battery, together with sustained high amp draw increase the risk for cell failures for a already weak performing battery.

If batteries are totally unmonitored thing's like this will always happen airborne eventually ... most probably this battery was the weakest of your 3 & have showed signs of this in earlier flights in similar conditions but not as severe that an autolanding was triggered.

You pushed repeatedly for max Throttle & Elevator already from start in a below freezing environment in this flight as seen here by the Red & Magenta graph ... that was enough for this battery to fail in cell 3.

spamgnome · Feb 9, 2021

This happened to all three of my Air 1 batteries with fewer than 50 cycles on them. I can't say it enough. MONITOR your batteries with AirData! You will see that the "bad" cells precede a forced landing.

RayOZ · Feb 9, 2021

I wonder if cold temperature led to a bit of icing on props, causing the motors to draw more current from the battery, hence the warning about not enough force.

spamgnome · Feb 9, 2021

RayOZ said:
I wonder if cold temperature led to a bit of icing on props, causing the motors to draw more current from the battery, hence the warning about not enough force.

Icing, in addition to freezing temperatures, requires visible moisture. (i.e., clouds or rain)

slup · Feb 9, 2021

RayOZ said:
I wonder if cold temperature led to a bit of icing on props, causing the motors to draw more current from the battery, hence the warning about not enough force.

In this case that is highly unlikely. The dew point ... where 100% relative humidity is reached & water is released from the air was at a much lower temperature.

Also no pitch, roll or yaw instability was seen either before or after the "not enough force" message in the log (pink area below in the chart. Just there the voltage from cell 3 on the other hand, was down to 2,74V ... the battery couldn't keep the AC airborne anymore, plain & simple.

*EDIT*
Jeez ... just saw that I wrongly quoted @spamgnome post ... sorry for that, corrected

Mr Shamrok · Feb 9, 2021

In this situation, one of the battery capacities dropped due to which the auto-landing turned on. If your battery does not respond to the power-on button or does not charge or gives an error,will help you at this address [email protected]

MavicG · Feb 9, 2021

Thanks for all the input!

Here are Airdata links from the other 2 flights with the other 2 batteries. It looks like these batteries are degraded as well. Can someone take a look and let me know your opinion of the other 2 batteries?

boblui · Feb 9, 2021

Similar phenomenon is seen in these flight logs - whenever the motors were under high load, the cell voltage would drop to abnormally low levels. Circled belows are moments when full-forward stick input was applied in sport mode and the cell-voltage dropped to 3.2 ~ 3.5 V.

Unfortunately you have not updated the firmware and the app as advised in my previous post so the current drawn from the battery is unknown so it remains uncertain whether the batteries are bad or the current was abnormally high due to problems of the power system.

This is my M2P in sport mode and under full-forward stick. The current drawn is about 16 Amp. cell-voltage is around 3.7 V compared with 3.2 ~ 3.5 V in your case.

MavicG · Feb 9, 2021

boblui said:
Similar phenomenon is seen in these flight logs - whenever the motors are under high load, the cell voltage would drop to abnormally low levels. Circled belows are moments when full-forward stick input was applied in sport mode and the cell-voltage dropped to 3.2 ~ 3.5 V.

Unfortunately you have not updated the firmware and the app as advised in my previous post so the current drawn from the battery is unknown so it remains uncertain whether the batteries are bad or the current was abnormally high due to problems of the power system.

View attachment 123561
View attachment 123562

This is my M2P in sport mode and under full-forward stick. The current drawn is about 15 Amp. cell-voltage is around 3.7 V compared with 3.2 ~ 3.5 V in your case.

View attachment 123560

I am using the Smart Controller and the firmware was updated yesterday. Do you mean the Mavic 2 Pro firmware or the app on the Smart Controller? Thanks for the help!

boblui · Feb 9, 2021

MavicG said:
I am using the Smart Controller and the firmware was updated yesterday. Do you mean the Mavic 2 Pro firmware or the app on the Smart Controller? Thanks for the help!

Both the APP running in the smart controller and the firmware of the M2P. I am using the stock controller + iphone so may be the log produced by the smart controller has less info.

slup · Feb 10, 2021

MavicG said:
Thanks for all the input!

Here are Airdata links from the other 2 flights with the other 2 batteries. It looks like these batteries are degraded as well. Can someone take a look and let me know your opinion of the other 2 batteries?

It's well known that weaker & aging LiPo cells generates higher internal resistance ... this means that the discharge rate decreases. So putting a battery with decreased discharge rate under heavy load (like going full in Sport mode) will return a decrease in voltage... & if dropping to far it might fall under 3V which leads to major permanent damage of the battery which again means a increase for the internal resistance.

So it's the internal resistance that are the root cause to this ... misusing the battery regularly going down to too low voltages (discharge it too much), store it outside 3,7-3,8V, give it too many charge cycles, operate it in to high ... or low temperatures ... will all build up the internal resistance --> make it more & more prone to show large voltage drops under load.

Looking at a couple single flights will not give a hint of the true condition of the battery ... at most you will note that certain operational conditions give more & deeper voltage drops & larger deviations between the cells in the battery. It will be very hard based on this, to take a decision to remove it from flight duty & instead only use it for desk duties. All we can say is that all LiPo batteries come to this stage eventually ... the trick is to remove it in time before you have mishaps with low voltage triggering auto landings.

The only way to foresee this is to monitor the performance trend over all flights you do with the battery ... monitor max possible usage times, voltage deviations & the capacity trend. Airdata.com have that service in their payed subscriptions ... that can be a cheap insurance letting you remove a aging & bad performing battery in time.