The battery is already at a failsafe level

Armed, this battery would set off the battery failsafe at once, so arming is refused. “low voltage” and “critical voltage”: the voltage is under BATT_LOW_VOLT or BATT_CRT_VOLT right now; the BATT_LOW_TIMER delay used in flight does not apply here. “low capacity” and “critical capacity”: BATT_CAPACITY minus the mAh used since power-on is under BATT_LOW_MAH or BATT_CRT_MAH (a current sensor is needed for these). A threshold of 0 is off; BATT_LOW_VOLT is 10.5 V by default.

What to do, most likely first

1. The battery is discharged, or only USB is connected and the sensor reads a small stray voltage.

   CheckThe battery voltage on the ground station's main screen.

   FixFit a charged battery.

2. The thresholds were set for a battery with more cells.

   CheckDivide BATT_LOW_VOLT by your cell count. A full LiPo is 4.2 V per cell: a threshold above that fails every time, and thresholds for 6S fail a full 4S battery.

   FixSet the thresholds for the battery you fly; the Setup & Tuning Guide's battery failsafe step works them out from the cell count.

3. The voltage reading is too low: BATT_VOLT_MULT does not match the board's sensor.

   CheckCompare the shown voltage with a multimeter on the battery leads.

   FixCalibrate the voltage in the battery monitor screen until they agree.

4. “capacity”: this battery has flown since power-on, or BATT_CAPACITY is smaller than the threshold.

   FixFit a charged battery; set BATT_CAPACITY to the real capacity in mAh, and BATT_LOW_MAH and BATT_CRT_MAH to the reserve you want left, not to the amount you plan to use.

Parameters to look at

Where to do it:Setup & Tuning GuideFailsafe ExplainerSetup & Tuning Guide