What happends here?

[chatikib]

I was flying today and during the flight I suddenly got a message of 'critical low power'. My battery still had a residual value of 54%. The automatic 'emergency landing' was started.

I have the drone back without damage, but what can I learn from this? Can anyone tell me what's going on?

You will find a link to the log file here:
DJI Flight Log Viewer - PhantomHelp.com

 

[ROD PAINTER]

I am not a expert but it looks like you took off with 62% battery. Always take off with a fully charged battery. Taking off with 62% battery can throw off incorrect battery data.

 

[PhantomFandom]

I was flying today and during the flight I suddenly got a message of 'critical low power'. My battery still had a residual value of 54%. The automatic 'emergency landing' was started.

I have the drone back without damage, but what can I learn from this? Can anyone tell me what's going on?

You will find a link to the log file here:
DJI Flight Log Viewer - PhantomHelp.com

The more experienced log reading experts can probably contribute more than I can. I did not download the detailed flight log but what I see is that:

• You took off with a battery that was not fully charged. It is good practice to start every flight with a battery that is fully charged. Anything less and you can find yourself in a situation where the battery gets critically low very quickly.
• The speed readings look very strange. I see speeds near 250 MPH. Perhaps you have some issues with sensors on the drone.
• You can see that very quickly into the flight, the variance between the battery cells starts getting larger. This could be because you started with a low charge or there may be an issue with the battery.
• There is also a motor overload about 18 seconds into your flight. That could have been causing battery issues as well. It doesn't look like you were doing any violent maneuvers or high speeds at that point so perhaps there is a problem with one or more of your motors.

That's just my take from a quick look at the flight. I'm sure one of the log experts can shed way more light once they see the detailed logs.

 

[chatikib]

The more experienced log reading experts can probably contribute more than I can. I did not download the detailed flight log but what I see is that:

• You took off with a battery that was not fully charged. It is good practice to start every flight with a battery that is fully charged. Anything less and you can find yourself in a situation where the battery gets critically low very quickly.
• The speed readings look very strange. I see speeds near 250 MPH. Perhaps you have some issues with sensors on the drone.
• You can see that very quickly into the flight, the variance between the battery cells starts getting larger. This could be because you started with a low charge or there may be an issue with the battery.
• There is also a motor overload about 18 seconds into your flight. That could have been causing battery issues as well. It doesn't look like you were doing any violent maneuvers or high speeds at that point so perhaps there is a problem with one or more of your motors.

That's just my take from a quick look at the flight. I'm sure one of the log experts can shed way more light once they see the detailed logs.

Thanks for your comment. Yes, it is my fault that I started with a partially charged battery. I tell everyone that you should always start with a fully charged battery. And now I am guilty of this mistake myself.

The strange thing is that the drone reacted calmly and stably. I did not notice anything about the behavior of the drone.

 

[sar104]

It was a low-voltage issue that triggered autoland, caused by starting with a low battery. Specifically the smart battery controller threw the quaintly-named "VoltageLowNeedLand" flag:

 

[chatikib]

It was a low-voltage issue that triggered autoland, caused by starting with a low battery. Specifically the smart battery controller threw the quaintly-named "VoltageLowNeedLand" flag:

View attachment 110307

Thanks! Your information is very clear. I promised myself that I would never start again with a half-full battery. No matter how tempting it is.

 

[MotorCycle-Man]

I charged all my batteries one time a long time ago BUT i failed to charge one UP.....i went to fly and i flew three fully charged batteries.....Then i flew the last low charged one from a previous flight...I Thought why not its 53% charged.....I had a really bad scare when it went in return to home and rose UP to the 98 meters and flew about 150 feet then dropped down to land.....Scary part is this...During the flight i took off and moved to a better spot to fly from out of the sun......that was at least 150 from home point where i took off was ..The drone did what it was supposed to do....But i Thought it was going to Fly Away and crash in the many BIG High Oak trees all over the area.
No more Not fully charged flights for me !

 

[PhantomFandom]

I charged all my batteries one time a long time ago BUT i failed to charge one UP.....i went to fly and i flew three fully charged batteries.....Then i flew the last low charged one from a previous flight...I Thought why not its 53% charged.....I had a really bad scare when it went in return to home and rose UP to the 98 meters and flew about 150 feet then dropped down to land.....Scary part is this...During the flight i took off and moved to a better spot to fly from out of the sun......that was at least 150 from home point where i took off was ..The drone did what it was supposed to do....But i Thought it was going to Fly Away and crash in the many BIG High Oak trees all over the area.
No more Not fully charged flights for me !

Very similar thing happened to me just this past Thursday. I had charged my Mavic Air batteries a week ago for a planned roof inspection that then got cancelled. Thursday I took it with me to give a flying lesson. After the lesson, I decided to fly a bit myself as it was a beautiful day. First battery was perfect and lasted the normal amount of time. The second battery must have already started its auto discharge cycle. As soon as I powered up the MA, battery life showed as 67% so I just powered down and swapped to another battery. I was taking off from a small pier and was flying almost exclusively over the river. No way would I even attempt it with a partially discharged battery.
There's never any reason to take chances with your expensive craft. Charge the batteries before every flight and never use a partially discharged battery.

 

[tribar]

I see speeds of 250 mpH in this flightlog !
Can anyone explain this ?

 

[sar104]

I see speeds of 250 mpH in this flightlog !
Can anyone explain this ?

That looks like a PhantomHelp data parsing problem - those are not the actual velocities recorded in the flight log:

 

[chatikib]

I still have an additional question. When is it that there is too much demand for the battery? In other words, today I started with a loading percentage of 98% and landed with a percentage of 95% (just one photo). Does a battery need to be recharged or can it be used again? Does anyone have a guideline for such a situation?

 

[Meta4]

I still have an additional question. When is it that there is too much demand for the battery? In other words, today I started with a loading percentage of 98% and landed with a percentage of 95% (just one photo). Does a battery need to be recharged or can it be used again?

If you wanted to launch and fly again on the same day, that should be OK but if you put it away for a few days, definitely recharge before flying.

 

[chatikib]

If you wanted to launch and fly again on the same day, that should be OK but if you put it away for a few days, definitely recharge before flying.

Is there a rule of thumb for those situations? For example, if the battery is lower than 75% then reload it before starting.

 

[PhantomFandom]

Is there a rule of thumb for those situations? For example, if the battery is lower than 75% then reload it before starting.

I don't know if there is any published guideline, but my rule of thumb is:

• Full charge before I go out flying
• If I fly and land, I still fly with that same battery again until my battery gets down to about 30%. I always try to land before 30%
• If I go home with a battery that has been used in any way, I charge it before flying again.
• If I go home with a full battery and it sits for more than a few days, I fully charge it before heading out again.

 

[MotorCycle-Man]

PhantomFandom.......That sounds Xactly like my battery procedure also !...You have posted Great battery guide lines ! Thank you.