Need Help Investigating Premature RTL due to battery failsafe

Hi All
I used the initial tune parameters (18inch prop 6s battery) to set the battery failsafe parameter.
However my drone is prematurely executing an battery failsafe RTL at 23v. The battery failsafe is set to the default value as per the initial tune parameters.

I cannot make out where I am going wrong.


Why exactly do you think it was premature? You know there is voltage drop under load right?

It failsafed on capacity.
BATT_LOW_MAH,12800 (think about this 16000-12800=? …)

Hi @amilcarlucas, Yes I am of this.

Hi @dkemxr

Oh so its BATT_LOW_MAH parameter. My interpretation of this parameter was if the capacity used falls below 12800mah it would execute the Battery failsafe. I did not think that this parameter means you should have 12800mah in reserve.

Thanks @dkemxr at point it out, I’ll correct it and test fly!

Also, BATT_FS_VOLTSRC should be set to 0 or 1?

Ardupilot can estimate how much the voltage of your battery sags based on current and what the voltage would be after the battery had time to relax.
BAT_FS_VOLTSRC determines if the raw battery voltage or a sag-compensated voltage gets used to determine if a low voltage failsafe occurred.
When you use the sag compensated voltage you can input the manufacturer’s recommendations into BATT_LOW_VOLT and BATT_CRT_VOLT. For lithium-polymere it’s usually like 4.2V full, <3.6V low, <3.5V critical, <3.3V empty and <3V permanently damaged. All voltages per cell.
When you use the raw voltage you can input slightly lower values without damaging your battery.

Hi @Janno
Thank you for clearing my doubt.
As I don’t have the manufacturer data for the battery, I’ll stick with raw voltage.

Hi Everyone

I forgot to update you all on the progress.

I made the change from BATT_LOW_MAH =12800 to BATT_LOW_MAH = 3200 (which is 20% reserve for 16000mah battery)

The failsafe worked as intended.

Thank you everyone.

The problem has be resolved!

1 Like

Great to hear that it works :+1:t2: