Copter 3.4.1 - crash because of battery failsafe

I am a new and I would like to understand the reason of my crash. From the logs I see a battery failsafe error although my battery voltage at that time was 11.2V.
2016-11-06 11-04-15.bin (2.1 MB)

From a quick look at the logs, your battery voltage under load was about 10.5V dropping to 10.1V at times.
Your battery failsafe is set to 11V but you don’t have it enabled.
Just after 48000 in the log the current drops to half when a demand is made for more power, evidently to stabilise, but it is not available.
Your starting voltage was only 11.4V so the battery was not fully charged from the start and drops to about 10.5V at the start of the flight.

The roll/pitch indicates a lot of oscillation so I am guessing you are over tuned and probably the lack power prevented proper stabilisation.

Do you have more details on the flight you could share?

thank you for your feedback. actually it was the second day experimenting still with the flight modes and the copter. From the previous day I increased the failsafe threshold but I didn’t enable it because I have not tested yet the relevant modes (i.e. RTL). Attached you can find in zip the logs from the flights the same day with the battery fully loaded. To avoid such situation in the future what are your suggestion? Fortunately from the crash I had a only a broken leg.

Also I provide a short video with the flight. (3.8 MB)

I run a few 3S copters and have the voltage FS set 9.9V
This is not particularly friendly to the batteries as it leaves only 9% to 12% in the pack, but I do not have RTL enabled just land and these copters do not do any great altitude excursions.
The batteries are also a high quality that don’t complain too much other than a bit of puffiness.
I would probably recommend about 10.2V to 10.4V for your setup which will give you ~20% left but only if you have Land as the failsafe.
If you want to RTL as the battery failsafe then 10.5V would be a safe level, depending on distances you might be wanting to RTL from.
Longer distances mean a higher battery FS voltage.
To begin with set it high, maybe even 11V and have an RTL as the failsafe.
When you recharge the battery see how much goes back in and work out the percentage you used for the flight.
That will give you a starting point to raise or lower the FS voltage.

1 Like