Mavic decided it was time to land

[serpa4]

I was out flying at 3,000 ft. I was assessing how long I can fly at full forward in normal mode P (i.e. not sport mode) roughly 18-20mph. I need to see if I can fly to the top of a local mountain, 3,000 climb and about 2.5 miles away. My intent was to climb to 3,000 and fly till the battery was at 10% and come home. I went straight up and them flew around in a 1/4 area not going far away. It ended up being 18 minutes, but was forced to land at 30% battery. My warning was set at 33% and critical at 15%. Just where I left them from playing with the setting weeks ago.
Here's what happened.
Went up to 3000.
Flew around for about 15 minutes at full forward pitch which varied between 18-20mph.
Got a low battery warning saying enough battery to get home. I immediately canceled it.
Later I got a voice prompt saying something to the effect Mavic is landing. It did not say returning to home, but landing. I was at 3,000 at the time. I had between 35-40% I think left.
I hit the red X to cancel it and the app closed.
I relaunched the DJI Go and got the same prompt, landing and I hit the red X and the app closed again.
I relaunched DJI Go and hit the red X again, but this time, got the prompt that said failed to cancel landing.
I hit it a gain and it displays failed to cancel landing again.
It started to descend and I couldn't stop it. I did have full directional control.
I flew it back to me within 20 seconds or so as I wasn't going far, just trying for flight time, but was still about 2000 feet up in an open area and no danger of landing on anything but a bush.
When the height bled off, and landed, I looked at the screen and it said 30% battery and the Mavic had one solid light and one flashing. So, there was a lot of battery left.
Why did it force land and why couldn't I stop it?

What confuses me was the prompt that said landing, not return to home when I landed with 30% battery left.
Page 14 of the manual says: The aircraft will land automatically if the current battery level can only support the aircraft long enough to descend from its current altitude. The user can still use the remote controller to alter the aircraft's orientation during the landing process.

This sounds like what I experienced, but at 30% battery.
I wonder if it was the height that screwed up it's calculations on what is required to decent from 3,000ft?
Can this be over ridden? 30% is a lot of wasted juice when I'm trying to get to a mountain top and back.

 

[Bunny Too]

I wonder if it was the height that screwed up it's calculations on what is required to decent from 3,000ft?
Can this be over ridden? 30% is a lot of wasted juice when I'm trying to get to a mountain top and back.

I think you are right, I think the Mavic thought it was much higher up than it was.

 

[msinger]

Why did it force land and why couldn't I stop it?

It sounds like the battery reached the critically low level. You can verify by uploading and viewing your TXT flight log here. If you need help reviewing it, post a link back here after you upload it.

Can this be over ridden?

No.

FYI, the 33% and 15% warnings will just alert you when the battery reaches those levels. That's not actually when the battery will reach the low and critically low levels.

 

[Kilrah]

I wonder if it was the height that screwed up it's calculations on what is required to decent from 3,000ft?

Nope they are correct. At the descent rate it uses during an automatic landing and given it will target to land with >10% 30 is already pretty low at 3000ft high.

 

[serpa4]

At 3000 ft, it would take "me" probably 5 minutes plus to land. Fastest I can come down is over a minute per 1000 ft. On a RTH landing it comes down much slower. I've never let a RTH landing finish since they are too slow.
I was at 5,000 once and it took 7:35 !!!! to come down AFTER I modified it to 7m/s decent in the software.
So, guessing that it lands much slower than me at full down, at 3000 ft it might think it takes 7 minutes to come down and hence, decided at 35% to force a landing.
Can this be disabled? I'll look this evening after work. Not sure if you can turn off the critical battery landing function. This would really suck as coming home down a mountain side it will start dropping height when I still have other peaks to clear! I need to come straight across home, then vertically landing to maintain LOS for controller signal.

That's what I thought....."FYI, the 33% and 15% warnings will just alert you when the battery reaches those levels. That's not actually when the battery will reach the low and critically low levels."

I've never pulled a log before. I had to go to bed prior to a 12 hour shift and didn't have time to research. Logs are on the mavic and accessible by the assistant when mavic is plugged in? There's noting (that I can see) on the memory card or my phone. I'll research at home this evening.

 

[serpa4]

I did fine a youtube feature to turn off the critical battery and RTH functions for a long distance or high altitude flight. nice it is software, so can turn it back on easily after a flight (using my PC). At least I don't have to flash FW to turn it on/off. I'll disable it for this mountain climb and re-enable post flight since the smart battery stuff help keep the mavic in one piece and keeps it from falling on people's heads.

 

[Xtreme Drone Pilot]

Nope they are correct. At the descent rate it uses during an automatic landing and given it will target to land with >10% 30 is already pretty low at 3000ft high.

Yep. If my hypothesis about the origin of the 500m ATOP limit is correct (it takes about 10% to descend from 500m at default 3m/s), then the app estimates it would consume almost 20% from 3000ft (straight down, not counting horizontal distance), plus it probably uses 10% of critical battery level as a goal for Smart RTH, so we already have ~30% where it would initiate Smart RTH.