Only 50% of battery consumed before failsafe


I have a quad with T-motor 4004 motors, T-motor 4 in1 ESC and 6s 10000 mAh Li Ion battery. The average current draw is 10A. I get a flight time of about 20 min before the copter goes into failsafe, set at 21.6V. But the mAh consumed is only 4000 mAh. While charging the battery, around same current goes in. What could be the reason that voltage drops quickly?


Take a look at BATT_* parameters.
You need to set voltage and current related parameters that suit your case.

The BATT_AMP_PERVLT and BATT_VOLT_MULT have been set correctly using an external power monitor. Should I set BATT_FS_VOLTSRC to 1?

In your case, BATT_CRT_VOLT triggers the failsafe. Set to 0 to disable if you want to fly more but closely monitor the voltage and current during flight.

BATT_CRT_VOLT is set to 0. The failsafe is triggered by BATT_LOW_VOLT, which is set to 21.6V.

For 6S Li-Ion you should definitely use these
Just make sure the voltage sensor is calibrated correctly at the lowest expected voltage (who cares if it’s a bit wrong at higher voltages)

Always have these set too:

If you use the initial parameters calculater (press Alt A in MissionPlanner or go to Setup, Mandatory Hardware…) it allows you to specify your battery and prop size and gives you the required settings.