Lost Mavic 2 Pro, battery depleted 1% very 2 seconds on return to home point

[NickSpender]

Hello

So flew my MP2 straight out. Flew out to 54% (yes I ignored low battery rth warning = yes I'm an idiot) in sport mode.

Now the I'm confused about apart from it dropping into a field at 0% in the fact that at 54% in turn 180 degrees and returned back to me. I noticed soon after turning 180 degrees the battery was depleting at a huge rate. 1% for every 2 seconds. It's it have a chance to get even close to the home point. Any ideas. Please don't keyboard bash me to much

 

[BB Baggins]

What about wind speed? Flying into the wind can use significantly move power.

 

[NickSpender]

Ah right that could have been it

@sar104 any chance you could take a look?

Worth uploading fly record.

More than anything I'd like to learn from this experience and make sure I don't put my self in the same situation

 

[PhantomFandom]

Hello

So flew my MP2 straight out. Flew out to 54% (yes I ignored low battery rth warning = yes I'm an idiot) in sport mode.

Now the I'm confused about apart from it dropping into a field at 0% in the fact that at 54% in turn 180 degrees and returned back to me. I noticed soon after turning 180 degrees the battery was depleting at a huge rate. 1% for every 2 seconds. It's it have a chance to get even close to the home point. Any ideas. Please don't keyboard bash me to much

So many factors here:

• NEVER ignore the RTH warning. It is there for a reason.
• I am assuming you flew downwind first? If at all possible always fly upwind first to make the trip home easier.
• What was the battery level before you started flying? Was the battery very recently charged to 100% ? Never start a flight with less than a fully charged battery.
• What altitude were you flying at? Did you check to see what the wind speed was at altitude? If you have high winds and are running low on battery, descend to a lower altitude where the winds may be lighter.
• I always plan on getting back and landing with no less than 30% battery remaining. Even more if I know I will have a headwind on the return trip. That means if I fly straight out somewhere, I start looking for a return trip at around 65% battery. In this case, turning around and starting your trip back at 65% would have most likely given you enough buffer to make it home safely.
• If you were flying all out full speed in sport mode then you were using even more battery power. It changes based on the drone and other conditions but generally your best distance will be achieved around full speed when in P (not Sport) mode.

 

[NickSpender]

I need to check the flight log regarding wind speed etc. Battery had recently been charged. Was at 100 or 99% no less. As I said I know I'm an idiot. The rth warning is there for a very good reason. Lesson learnt there. That very interesting regarding getting better distance on P mode than on Sport mode.

 

[tleedom]

Follow these instructions and post a link back here.
DJI Flight Log Viewer | Phantom Help

 

[Mossiback]

The sweet spot for battery life is in P mode with forward sensors off. It gets you speeds between P and S mode without the over-sensitive sticks of S mode. You just have to rely on yourself instead of sensors to keep from running into something (as you should anyway).

 

[sar104]

Ah right that could have been it

@sar104 any chance you could take a look?

Worth uploading fly record.

More than anything I'd like to learn from this experience and make sure I don't put my self in the same situation

Sure - post the log as described in #6.

 

[NickSpender]

Sure - post the log as described in #6.

Thank you

 

[NickSpender]

The sweet spot for battery life is in P mode with forward sensors off. It gets you speeds between P and S mode without the over-sensitive sticks of S mode. You just have to rely on yourself instead of sensors to keep from running into something (as you should anyway).

Stupid question how do you turn the forward facing sensors off in P mode?

 

[NickSpender]

@sar104 here you go

DJI Flight Log Viewer | Phantom Help

Upload and view DJI Phantom, Mavic, and Spark flight logs online

www.phantomhelp.com

 

[sar104]

@sar104 here you go

DJI Flight Log Viewer | Phantom Help

Upload and view DJI Phantom, Mavic, and Spark flight logs online

www.phantomhelp.com

The depletion rate was normal - the fairly modest increase in rate on the return was due to the higher pitch required to battle the headwind (~ 20 mph out of the SW). Note the depletion rate is strongly dependent on the pitch:

 

[NickSpender]

So basically lessons learnt are
- take note of low battery rth message / warning
- P mode would have probably beeny best friend
- check wind speeds / direction of wind speed

 

[NickSpender]

@sar104
Do you think the last recorded are accurate. I.e is it in river

 

[Gryphon962]

If I'm reading those plots right, the Battery RTH warning would have come on at 76%, 4m 5sec into flight. The last 50% of the battery was expended in 400 secs, ie 8 secs per percent. Battery life was 17 minutes to 0%. Interesting that it flew for almost 2 minutes showing 0% battery.

Concur on the comment about best range being P mode with Obstacle Avoidance setting off, BUT that is in still air. In a headwind, without getting academic, the faster the better (as you have to minimize time spent with wind pushing you away).

 

[Mossiback]

In a headwind, it is better to change height in hopes of finding less wind to fly against.

 

[sar104]

@sar104
Do you think the last recorded are accurate. I.e is it in river

Connection was lost because the cell voltages collapsed, as expected:




That means it effectively fell from its last recorded point. Simulating the descent with the wind field calculated from the AirData aerodynamic model and using a reasonably accurate drag model for the Mavic produces the following:



On Google Earth, that maps as:




So yes - I'm afraid that it is almost certainly in the river.

 

[Gryphon962]

I took the liberty of opening sar104's excellent graph in an editor to see what would have happened if the OP had turned around when the Battery RTH warning came on, and flew home at the same speed and battery drain rate that he got when he (eventually) turned around.

My estimate is that the drone would have landed back at the HP after just 11mins in flight, with 18% battery. I'll spare you seeing edited graph as its a mess, but can anyone validate that estimate using same or similar method? I'm stunned that a M2P could burn through a battery to 18%, even in S mode, in 11 mins.

 

[Thomas B]

To OP, hope the drone is in a tree or something and not in the water.
One point I didn’t see is one I have as a full for myself: Whenever possible, even if I have to move TO point significantly, always fly out against the wind and back with it.
The rest is well stated above.
Hope you get your drone back. Keep us informed.

 

[sar104]

I took the liberty of opening sar104's excellent graph in an editor to see what would have happened if the OP had turned around when the Battery RTH warning came on, and flew home at the same speed and battery drain rate that he got when he (eventually) turned around.

My estimate is that the drone would have landed back at the HP after just 11mins in flight, with 18% battery. I'll spare you seeing edited graph as its a mess, but can anyone validate that estimate using same or similar method? I'm stunned that a M2P could burn through a battery to 18%, even in S mode, in 11 mins.

I get return to HP at around 12 minutes 30 seconds, with around 30% battery remaining. As for the short flight time, you will notice from the graphs above that most of it was spent in sport mode with full forward elevator. I'd say that 19 minutes of flight time, as achieved, is pretty good.