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Mavic Pro fell off like a dead weight while landing

lavkesh

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Hi Fellow Pilots,

I have had my mavic pro for a couple of months now and this is the first time it happened and it has made me anxious, so anxious that I am scared to fly now lest it decides to drop out again. This is what happened. I started flying my Mavic Pro on a full battery to check out some of the setting. Flew around from my back yard mostly within line of sight and about 5 minutes out of sight at an altitude of around 150-170 meters. As the battery neared 30% I initiated RTH and cancelled it when it came up straight over my head. Seeing that the battery was still around 28%, I started testing the fixed wing mode and then put it into sport mode to test the speed. All this while it was in my line of sight and as the battery went below 20% I brought it down within my backyard to about 2-3 meters in height and then did a couple of quick acceleration and deceleration runs in the backyard. The battery now went below 15% and I lined the drone up to my landing pad wanting to land. While I was doing that, about 2-3 feet above with the battery at 13%, my Mavic Pro just shut off (disconnected on the DJI app, all LED's off) and fell like a dead weight. Luckily it was not too high and the landing pad was in my backyard with grass so no damage at all.

I started searching online to figure out what went wrong (CsvView and Dat viewer) but could not figure out what is wrong. I have attached the file here. Can anyone help me in figuring out what went wrong here. Thanks in advance.
 

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lavkesh

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You went too far on the battery. Normally you should land at 25-30%.
That is good practice and preserves the life of the battery.
At 13% the voltage is too low to properly operate.
Thanks. But why did it shut off and became a dead weight with the battery @ 13%? Can anyone analyse the logs or help me in what to look for? Thanks.
 

ac0j

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The battery is not full until it reaches empty. It gradually loses voltage as you fly, when the voltage gets to low, it shuts off. Charge percentage should not be looked at like a fuel gauge, look at it more like the percentage of a chance of a successful landing. The lower you run it, the better chance you are going to have a problem.
 
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lavkesh

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Thanks guys. Also looking for help in analysing the logs before I fly again. Is the battery failing? How can I tell?
 

Keule

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Is the battery failing?
Your battery cell #2 is out of balance. That means the % indicator remaining were not accurate.
ALWAYS look at the battery voltages and not at the %. (To be on the safe side, be sure to be on the ground when one cell is at 3.5v when flying)

Bildschirmfoto 2018-07-04 um 07.02.24.png
 

lavkesh

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Your battery cell #2 is out of balance. That means the % indicator remaining were not accurate.
ALWAYS look at the battery voltages and not at the %. (To be on the safe side, be sure to be on the ground when one cell is at 3.5v when flying)

View attachment 41310
Brilliant. Thanks for this. Does it mean that I need to replace the battery or go through one complete discharge and charge cycle?
 

Keule

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Does it mean that I need to replace the battery or go through one complete discharge and charge cycle?
Try a full discharge, and then charge fully.
Watch the voltages of each cell while hovering, or any warnings from GO4.

If cells deviate more than 0.07v or more while under load, i would not trust the battery anymore.
 

lavkesh

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Try a full discharge, and then charge fully.
Watch the voltages of each cell while hovering, or any warnings from GO4.

If cells deviate more than 0.07v or more while under load, i would not trust the battery anymore.
When you say under load, would just hovering put enough load? Thanks a bunch.
 

GerdS

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I guess this battery, especially cell 2 is damaged due to flying it too often until fully discharged or other mishandling. I would not trust it anymore.
 

lavkesh

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Bad news! Was discharging the battery fully by hovering and my mavic pro started drifting on its own and went close to the wall. I panicked and did not realise I pushed the wrong stick in the wrong direction given the orientation. Went into the wall and fell down on the gimbal breaking the mounting plate :(
Devastated!
 

aokusman

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Bad news! Was discharging the battery fully by hovering and my mavic pro started drifting on its own and went close to the wall. I panicked and did not realise I pushed the wrong stick in the wrong direction given the orientation. Went into the wall and fell down on the gimbal breaking the mounting plate :(
Devastated!
What happened to your sensors? The mavic should have stopped.
 

WAXMAN

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Thanks. But why did it shut off and became a dead weight with the battery @ 13%? Can anyone analyse the logs or help me in what to look for? Thanks.
Maybe you accidentally turned both the control sticks inward or outward. Just guessing.
 

Youser

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Bad news! Was discharging the battery fully by hovering and my mavic pro started drifting on its own and went close to the wall. I panicked and did not realise I pushed the wrong stick in the wrong direction given the orientation. Went into the wall and fell down on the gimbal breaking the mounting plate :(
Devastated!
Next time you want to test similar things, make sure there are no walls around. I always carry out my tests in an open field.
 
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