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

[NickSpender]

Everyone thank you so much for all your input. @sar104 your graph's and calculations always impress me. One thing I'm unsure of is. How do I turn obstacle avoidance off while non P mode?

 

[Thomas B]

Everyone thank you so much for all your input. @sar104 your graph's and calculations always impress me. One thing I'm unsure of is. How do I turn obstacle avoidance off while non P mode?

In ATTI it is off by default I believe. I presume your not going to beginner mode.
Here’s a link to the full (70+ page) manual;

https://dl.djicdn.com/downloads/Mavic_2/20190417/Mavic_2_Pro_Zoom_User_Manual_v2.0_en_.pdf

 

[RayOZ]

8.5km out. > than the quoted 8000m (FCC) in the manual. You were 10 mins in flight before you turned around. I think you'll barely get 20mins flight time in sports mode, even on a windless day. It was never going to make it home.
I haven't tested battery efficiency for the M2P. With MP1:
P-Mode OA on, max speed 36kph.
P-Mode OA off, max speed 50kph
S-Mode, max speed 65kph.
I found the 50kph is the sweet spot for MP1.
With M2P, P-Mode OA on is already 50kph. (my last test flight, I was flying at almost constant 50kph. 100% to 28% in 18:50, almost windless day)

What you should've done in your scenario is by 10%, you start looking for a safe spot to land. You'll just have to drive to the spot to retrieve it.
If you had more than 1 battery, you could flown once, turn back when the warning appears and see what battery % you had left when you land. If it was at comfortable level, then use the next battery to go a bit further.

 

[paulatkin73]

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

just as a generic comment - it is not an idiocy, just a bit lack of skill - so, to clarify what would be best - when you take off and go, every time you need to establish first the direction of the wind. best way to do it is to have a switch for the ATTI mode, so when you get drone up to the desired altitude - you switch to ATTI and then you will _see_ with your own eyes how fast and where it drifts.
it is obvious to presume that going back against the wind will require way more power. so, next best idea - choose the home spot to start the flight against the wind, so you will come back with the wind.

now, the sport mode, and a hacked sport mode with more aggressive angle will get you to the destination faster and it is good, but, it drains way more current and depletes battery way more. so, the best most effective speed/power mode is actually a stock RTH mode when you click it on your controller. in ideal no wind circumstances it will give you maximum distance. now, it is not all the times true, but, it is better to use in most times than to jerk drone in panic. definitely do not push back in sport mode, UNLESS wind is too strong for P mode to deal with it. it just needs to be remembered that sport mode speed kills your max distance.

without going into too many other details - first thing to do in a situation like this is to decide if you can safely lower down where you have less wind, as that is the most important thing that will help you to get back. then, use your brain - it is same how to swim against the rip current - see if you can go sideway to clear the water and be above ground faster - that, again, requires to be aware of the wind direction. it was always a very odd thing to me of why DJI did not put there into the GO4 app any kind of a wind speed indicator - it would help so much and it is so easy to do, but, it is what it is.

last - again, it requires no panic and calm thinking - estimate when power will run out, look carefully for a parking lot or a clearing and try to land where it is safe and away from traffic and people. then, drive there and pick it up.

Ps. under no circumstances run out of power above somebody else`s property. better sink it in the river as you did - you do not want a lawsuit to deal with if drone gets into somebody`s dinner table through the roof.

 

[paulatkin73]

In ATTI it is off by default I believe. I presume your not going to beginner mode.
Here’s a link to the full (70+ page) manual;

https://dl.djicdn.com/downloads/Mavic_2/20190417/Mavic_2_Pro_Zoom_User_Manual_v2.0_en_.pdf

to elaborate what said above - and it is also a general advice to everybody - have an ATTI swtich done. it is way more effective to go over long distance in ATTI, as, drone will not be spending power on fighting for position and stabilizing wind effects while you drive it where you want it to be. keep stock angle for P and ATTI modes, if you get to that level of params, as that angle is most power efficient one. modify sport mode angle and speed params only.

 

[CJH92474]

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

View attachment 75890


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:

View attachment 75892

On Google Earth, that maps as:

View attachment 75891


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

Sir, you are phenomenal!

 

[Mossiback]

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

On the main Go 4 screen tap the sensor icon or from the main controller settings page tap the second item down.



Then tap the slider to turn off OA.



When OA is on the speed is reduced so it can stop in time. With OA off it will fly faster, right into a brick wall if you are not careful.

 

[ElectroBald]

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.

If I can make a suggestion, when you do your flight plan, check the wind direction, speed and gust at the the altitude you plan to fly.

I use the UAV Forecast app, for that kind of information, if I see that there is winds higher than the recommended maximum in my drone manual, then I try to fly lower.

Example, where I live today, if I fly at 50m the wind speed is 14kph, but if I go up to 100m, the wind is at 32kph with gust of 76kph.

If you fly with the wind it will be way easier on the battery, but if you come back against high winds, then you might not be able to RTH, even though the drone app tells you that you can; read your manual as well to see the max wind for your drone, and keep in mind that your battery works harder against winds.

 

[jacquespa]

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

View attachment 75890


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:

View attachment 75892

On Google Earth, that maps as:

View attachment 75891


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

Wow, as Maxwell Smart would say: "missed it by this much."

 

[johnmeyer]

Question: how do you get wind speed from those flight log charts?

Comment: I'm not sure that increasing the speed when returning home is going to get you the most distance on whatever charge remains in the battery. Wind resistance goes up as the square of the drone's forward speed + wind speed. There is probably some simple algebra or calculus equation that would determine the optimum speed, but you'd have to know the energy/rpm/speed equations for the drone.

 

[sar104]

Question: how do you get wind speed from those flight log charts?

The FC computes wind speed but the results are not included in the txt logs - only the DAT logs. Without them you need an aerodynamic model for the aircraft that uses attitude and velocity to estimate wind speed. The AirData website has that, so I generally get them from there.

Comment: I'm not sure that increasing the speed when returning home is going to get you the most distance on whatever charge remains in the battery. Wind resistance goes up as the square of the drone's forward speed + wind speed. There is probably some simple algebra or calculus equation that would determine the optimum speed, but you'd have to know the energy/rpm/speed equations for the drone.

You might be interested in the discussion in this thread. Note that I got my first calculation wrong however, so you need to keep reading.

Physics of Drones

Give a drone to a physicist and he/she is likely to want to know how it works. Those with some science background might like to see http://homepages.abdn.ac.uk/nph120/meteo/DroneFlight.pdf. The article includes power consumption for hovering, rising and moving forward, estimated from mechanics...

phantompilots.com

 

[Gryphon962]

Question: how do you get wind speed from those flight log charts?

Comment: I'm not sure that increasing the speed when returning home is going to get you the most distance on whatever charge remains in the battery. Wind resistance goes up as the square of the drone's forward speed + wind speed. There is probably some simple algebra or calculus equation that would determine the optimum speed, but you'd have to know the energy/rpm/speed equations for the drone.

True, its is possible to go into some academic depth on the topic to determine how fast you should go into wind to achieve max range for any specific drone. However, the fact that you should go faster is easily proven by the extreme example of having a drone (speed 30 mph) going into a 30 mph wind, in which case, range = 0 until you go faster.

Another misconception among those not used to flying is that the effect of a head/tail wind balances out and therefore doesn't impact your range. That is (very) wrong as you suffer the impact of flying into the wind for longer than you benefit from flying downwind. Even if the wind is a crosswind, the air distance flown both out and back will be greater than the ground distance flown.

Finally, the common theme I'm seeing in these 'I lost my drone as it ran out of battery' threads is that users think they have 100% of battery to use, so turning at or near 50% will work. Given the lowest low battery setting is 20%, they only have 80% to play with, of which 'halfway' is 60% (still air).

 

[ItsDarts]

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

I pushed my limits today with the M2P. I only pushed it because it was a hyperlapse on the way to the home point. I was at picture 180 when i got the notice and canceled that notice. told myself id stop at 200 of 250 pics. I did that and initiated RTH... on its way home, it said enough and stopped and started landing, luckily only 20 yards from home in a field. I interupted the forced landing sand flew it to the pad, barely. still had 5%. they dont fool around, head their RTH warnings, save your battery and shorten recharge time, which is useful for in-field charging with power packs.

 

[Thomas B]

I pushed my limits today with the M2P. I only pushed it because it was a hyperlapse on the way to the home point. I was at picture 180 when i got the notice and canceled that notice. told myself id stop at 200 of 250 pics. I did that and initiated RTH... on its way home, it said enough and stopped and started landing, luckily only 20 yards from home in a field. I interupted the forced landing sand flew it to the pad, barely. still had 5%. they dont fool around, head their RTH warnings, save your battery and shorten recharge time, which is useful for in-field charging with power packs.

Agree. When I push the hyperlapse time I always do it within 200 or so yards from home.

 

[Juergen64]

I'm stunned that a M2P could burn through a battery to 18%, even in S mode, in 11 mins.

As i surprised noticed in past, the sport-mode has an big impact to the Flight Air Time.

The linked example shows a battery usage of 77% in just 13 minutes even there was (almost) no wind.


It looks, the sport-mode should be used with care.

 

[paulatkin73]

As i surprised noticed in past, the sport-mode has an big impact to the Flight Air Time.

The linked example shows a battery usage of 77% in just 13 minutes even there was (almost) no wind.


It looks, the sport-mode should be used with care.

You have a 3Ah battery on the bird. Faster speed and extra activity increases amount of consumed current. Racing drone has roughly 5-7 min flight time as it can burn up to 60-80A while lipo can sustain it. Mavic at loiter burns about of 7-8A, similar during stock RTH mode. Sport mode pushes it closer to 14-17A max, on my drone at least. So, it means 2 time shorter flight time.

 

[RWD]

WOW. I am amazed by the information posted from the flight logs. I am completely new to this forum and to drone flying. Is there something I can find that documents what can be found in the logs, and how to extract that into graphs like Mr sar104 generated, and the amazing link to the Google Earth showing flight path?

I would really like to learn how to do this, so any and all guidance or reference material would be appreciated. Thanks folks.....

 

[JSM]

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

Nick, did you recover the craft ?????

 

[johnmeyer]

You have a 3Ah battery on the bird. Faster speed and extra activity increases amount of consumed current. Racing drone has roughly 5-7 min flight time as it can burn up to 60-80A while lipo can sustain it. Mavic at loiter burns about of 7-8A, similar during stock RTH mode. Sport mode pushes it closer to 14-17A max, on my drone at least. So, it means 2 time shorter flight time.

I didn't know any of that. This is really useful information. Thanks for posting this!

 

[RayOZ]

FYI. I tested my M2P, P-Mode OA on and off, both have max speed of 50 kph. So I am leaving the OA on.