Today while returning to home, the "Low battery" message appeared just at the same time as the drone would not go any faster than 4 m/s even after pushing the throttle forward fully several times. I was in Normal mode all the time. Fortunately I was close enough, but is that normal that the speed becomes limited on low battery? The battery level was 20%... Can it be a bad cell?

Low altitude will lower maximum speed!

Where is it written that the speed is reduced when the battery level is low, at high altitude and / or at low altitude ??

Upload a log to one of the free log viewer sites and take a close look at what was happening.
https://www.phantomhelp.com/LogViewer/Upload/

Pinarek Posted at 9-25 15:04
Where is it written that the speed is reduced when the battery level is low, at high altitude and / or at low altitude ??

however, to be fair he did mention "maximum" in his reply which makes it sorta a different reply than your question asks.  will a drone which has triggered rth at a low altitude encounter a maximum speed restriction?

i don't deal with this much but i always thought you couldn't couldn't speed up or slow down the rth function (only raise or lower it plus) unless you cancelled it and upon low battery rth, even less; no?

I wasn't using RTH, I was flying straight to home  at 10 m/s when I hit 20% battery and the drone slowed down, just a second before the "Low Battery" appeared in red... After that I tried to accelerate but couldn't go above 3-4 m/s. I also wasn't ascending or descending at all, altitude should not have played any role. I briefly tried RTH but cancelled right away because my RTH altitude was set higher and I didn't want the drone to climb at this point.
For those suggesting to upload the flight log, that is impossible, the logs are encrypted. But what I described is exactly what I see when playing back the recorded flight in the app. I could probably record a video of the playback and post it here.

EDIT: Sorry now I feel stupid.. I didn't realize the logs have to be downloaded from the phone and not the drone itself... I will upload the TXT to the phantomhelp website

Here's the link to the flight log CSV with coordinates and serial numbers removed.
https://drive.google.com/file/d/ ... VQ/view?usp=sharing
The issue starts around 17m31.

Turbo1ed Posted at 9-25 20:12
Here's the link to the flight log CSV with coordinates and serial numbers removed.
https://drive.google.com/file/d/1W-CvK07379MjSxOcbuH7W_aPcXlBo_VQ/view?usp=sharing
The issue starts around 17m31.

Could you please post a link to the log viewer, that way we can see whats going on, excel is hard to read without a viewer on hand?

Turbo1ed Posted at 9-25 20:12
Here's the link to the flight log CSV with coordinates and serial numbers removed.
https://drive.google.com/file/d/1W-CvK07379MjSxOcbuH7W_aPcXlBo_VQ/view?usp=sharing
The issue starts around 17m31.

Hi Turbo1ed,

No problem to hide or delete some fields in your CSV bc of your privacy, all other relevant fields are in the CSV.

Yes, it is normal to reduce output power when battery gets real low.

Afaik this is for a Mini10 at 10% battery level and lower, not at or around 20%.
But i have seen few messages "critical battery level" starting at 20% now, before this message was seen at 10%....did DJI change this ??
Chart of your data shows indeed lower speed with fully forward stick.

Is this normal ?  well, in one of my last flights with a MINI2 ; at 20% batt in RTH a normal speed value of 10.7 m/s.

at 17m43.3s in flight : Batterie dangereusement faible, but batt values that time cell1 = 3.646 and cell2 = 3.620, so good and normal values for 19% battery level.a misreading of values by the software so the output power was reduced? (but no error message about this...)

cheers
JJB

Turbo1ed Posted at 9-25 20:12
Here's the link to the flight log CSV with coordinates and serial numbers removed.
https://drive.google.com/file/d/1W-CvK07379MjSxOcbuH7W_aPcXlBo_VQ/view?usp=sharing
The issue starts around 17m31.

If you want help, please post the actual flight data., not a doctored CSV file.

Pinarek Posted at 9-25 15:04
Where is it written that the speed is reduced when the battery level is low, at high altitude and / or at low altitude ??

Hi,

Try yourself....

Fly in N mode with 100% forward stick and lower to real low altitude above flat surface ; max speed will decrease
Fly in N mode with batt level < critical value ; you will get a msg on the screen and output power is reduced = lower speed
Fly in N mode at high altitude ; uhh, never did that so no idea if in thin air max speed is reduced.

Written in the manual ? nope, as many issues are not to be found in the manual.

cheers
JJB

Labroides Posted at 9-26 02:22
If you want help, please post the actual flight data., not a doctored CSV file.

Here's the airdata link https://app.airdata.com/share/Xnnakk

Turbo1ed Posted at 9-26 05:43
Here's the airdata link https://app.airdata.com/share/Xnnakk

But you haven't ticked "share" so I still can't see the actual data

JJB* Posted at 9-25 23:58
Hi Turbo1ed,

No problem to hide or delete some fields in your CSV bc of your privacy, all other relevant fields are in the CSV.

HI JJB
There seems to be a discrepancy between the message shown in the DJI Fly app and what's in the log. When I do the playback in DJI Fly, the "Low Battery" warning appears but not "Critical Low Battery".
I noticed in the data the battery temp seems to have peaked at that moment...

Turbo1ed Posted at 9-26 06:35
HI JJB
There seems to be a discrepancy between the message shown in the DJI Fly app and what's in the log. When I do the playback in DJI Fly, the "Low Battery" warning appears but not "Critical Low Battery".
I noticed in the data the battery temp seems to have peaked at that moment...

well, i do not see many logs in French...

But at 19% batt level, if i translate correctly, indeed both messages in the log ;
"Batterie faible" et "Batterie dangereusement faible"....
Guess the last message for the reduced output power.

Batt temperature looks normal, slowly getting higher from 25.9  to  47.9 Centigrade, not really a peak somewhere.

cheers
JJB

Turbo1ed Posted at 9-26 05:43
Here's the airdata link https://app.airdata.com/share/Xnnakk

Thanks for the link .. I registered with a free account right away, I will update to gold later.

You can really follow what you have flown where and when.
Is similar to www.phantomhelp.com

JJB* Posted at 9-26 06:49
well, i do not see many logs in French...

But at 19% batt level, if i translate correctly, indeed both messages in the log ;

Sorry about the French log
The critical battery message starts appearing only 30 seconds after the initial slow-down.
The only thing I noticed so far is the battery temperature reached its highest (119.3 F) a bit before that slow-down moment, then it started cooling down (due to lower speed/load, I guess)
I already reached out to DJI support, hope they will shed some more light on this...

Here is the battery temperature graph, seems to have jumped up quite a bit for no reason around the 7m and 12m mark. The peak happens around 17m35s exactly when the slow-down happens.

Yeah, looking at the notifications, it looks like the battery, as it was dangerously low, it would only get back in time if it slowed it down for you, that's what happened and that's what does happen, its normal

Turbo1ed Posted at 9-26 08:15
Here is the battery temperature graph, seems to have jumped up quite a bit for no reason around the 7m and 12m mark. The peak happens around 17m35s exactly when the slow-down happens.

[view_image]

its not jumping, disconnect for 81 seconds, in that period temp increased normally  but this chart does not show the disconnect!
Max temp in centigrade  48.5, after that 47.9!  so almost flat line at the end, minor drop in temp! so no peak and drop to worry about.

Batt cell values in my chart, all oke!  so no dangerous low values ect...

cheers
JJB

Turbo1ed Posted at 9-26 05:43
Here's the airdata link https://app.airdata.com/share/Xnnakk

Data?
Are you going to post actual data?
A link to the Phantomhelp report would be ideal.

It has been known for the speeds to be limited by a downward looking gimbal.

You seem to point the gimbal down around 17:11.

I encountered this, again, a couple of days ago with either my Mavic Mini or my Mini 2 and it took me a few seconds to realise the cause.

Labroides Posted at 9-27 03:43
Data?
Are you going to post actual data?
A link to the Phantomhelp report would be ideal.

Hi Labroides,

Why the need for latlon data and other privacy data, all other needed fields are in the csv ; just curious.

cheers
JJB

Sean-bumble-bee Posted at 9-27 04:18
It has been known for the speeds to be limited by a downward looking gimbal.

You seem to point the gimbal down around 17:11.

Hi,

Good find!  good to check the next times for me , added it to my brain cells  ;-)

And for my 'old' brain cells...added it to FRAP as a reminder....     ;-)
(NoGps because OP removed its LatLon data...)

cheers
JJB

Labroides Posted at 9-27 03:43
Data?
Are you going to post actual data?
A link to the Phantomhelp report would be ideal.

I would be glad to share the data if I can remove my coordinates... That is like giving my home address to the world.

Sean-bumble-bee Posted at 9-27 04:18
It has been known for the speeds to be limited by a downward looking gimbal.

You seem to point the gimbal down around 17:11.

THAT'S IT!!!
It's also documented in the user-manual:
I was preparing for landing, that's when I pitched down. I flew with the gimbal down a lot of times but never paid attention to the speed until now...
Thank you!

Turbo1ed Posted at 9-27 05:59
I would be glad to share the data if I can remove my coordinates... That is like giving my home address to the world.

Forget it then ... I don't care where you live in Canada, but need full data for proper analysis.

Labroides Posted at 9-27 15:28
Forget it then ... I don't care where you live in Canada, but need full data for proper analysis.

What's your home address?

Turbo1ed Posted at 9-27 06:24
THAT'S IT!!!
It's also documented in the user-manual:
[view_image]I was preparing for landing, that's when I pitched down. I flew with the gimbal down a lot of times but never paid attention to the speed until now...

Hi

i did a test with my MINI2,

100% forward stick > 9.9 m/s (against some wind).
Camera down move and at -80 degrees speed start to slow down, at -90 degrees down speed 4.2 m/s

100% forward stick and camera zero degree > 7.5 m/s, camera not at zero degree ful speed again.

cheers
JJB