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fix(commander): combine all battery failsafe configuration into COM_LOW_BAT_ACT to make the options very clear for the user

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Matthias Grob
2026-04-02 17:57:57 +02:00
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docs/en/config/safety.md
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@@ -77,37 +77,29 @@ QGC allows users to set some aspects of the landing behaviour, such as the time
### Battery level failsafe
The low battery failsafe is triggered when the battery capacity drops below battery failafe level values.
The low battery failsafe is triggered when the battery capacity drops below battery failsafe level values.
You can configure both the levels and the failsafe actions at each level in QGroundControl.
![Safety - Battery (QGC)](../../assets/qgc/setup/safety/safety_battery.png)
The most common configuration is to set the values and action as above (with `Warn > Failsafe > Emergency`), and to set the [Failsafe Action](#COM_LOW_BAT_ACT) to warn at "warn level", trigger Return mode at "Failsafe level", and land immediately at "Emergency level".
The most common configuration is to set the values and action as above (with `Warn > Failsafe > Emergency`), and to set the [Failsafe Action](#COM_LOW_BAT_ACT) to warn at "warn level", trigger Return mode at "Failsafe level", and land immediately at "Emergency level". The same parameter also controls the bingo fuel failsafe, which triggers Return mode when the estimated remaining flight time drops below what is needed to return safely (requires `BATn_CAPACITY` to be set).
The settings and underlying parameters are shown below.
| Setting | Parameter | Description |
| --------------------------------------------------- | ---------------------------------------------------------------------------- | ------------------------------------------------------------------------------------- |
| <a id="COM_LOW_BAT_ACT"></a>Failsafe Action | [COM_LOW_BAT_ACT](../advanced_config/parameter_reference.md#COM_LOW_BAT_ACT) | Warn, Return, or Land based when capacity drops below the trigger levels. |
| <a id="COM_LOW_BAT_ACT"></a>Failsafe Action | [COM_LOW_BAT_ACT](../advanced_config/parameter_reference.md#COM_LOW_BAT_ACT) | Action when battery capacity drops below the trigger levels, and for bingo fuel (flight time drops below return flight time). |
| <a id="BAT_LOW_THR"></a>Battery Warn Level | [BAT_LOW_THR](../advanced_config/parameter_reference.md#BAT_LOW_THR) | Percentage capacity for warnings (or other actions). |
| <a id="BAT_CRIT_THR"></a>Battery Failsafe Level | [BAT_CRIT_THR](../advanced_config/parameter_reference.md#BAT_CRIT_THR) | Percentage capacity for Return action (or other actions if a single action selected). |
| <a id="BAT_EMERGEN_THR"></a>Battery Emergency Level | [BAT_EMERGEN_THR](../advanced_config/parameter_reference.md#BAT_EMERGEN_THR) | Percentage capacity for triggering Land (immediately) action. |
| <a id="COM_ARM_BAT_MIN"></a>Minimum armable state of charge | [COM_ARM_BAT_MIN](../advanced_config/parameter_reference.md#COM_ARM_BAT_MIN) | Prevents arming if the battery state of charge is below the specified value. |
### Flight Time Failsafes
### Maximum Flight Time Failsafe
There are several other "battery related" failsafe mechanisms that may be configured using parameters:
The maximum flight time failsafe ([COM_FLT_TIME_MAX](#COM_FLT_TIME_MAX)) allows you to set a maximum flight time after takeoff, at which the vehicle will automatically enter return mode (it will also "warn" at 90% of this time). This is to comply with certain regulations where the mission has to be aborted if it takes longer than a certain amount of time. The feature is disabled by default.
- The "remaining flight time for safe return" failsafe ([COM_FLTT_LOW_ACT](#COM_FLTT_LOW_ACT)) is engaged when PX4 estimates that the vehicle has just enough battery remaining for a return mode landing.
You can configure this to ignore the failsafe, warn, or engage Return mode.
- The "maximum flight time failsafe" ([COM_FLT_TIME_MAX](#COM_FLT_TIME_MAX)) allows you to set a maximum flight time after takeoff, at which the vehicle will automatically enter return mode (it will also "warn" at 90% of this time). This is like a "hard coded" estimate of the total flight time in a battery. The feature is disabled by default.
- The "minimum battery" for arming parameter ([COM_ARM_BAT_MIN](#COM_ARM_BAT_MIN)) prevents arming in the first place if the battery level is below the specified value.
The settings and underlying parameters are shown below.
| Setting | Parameter | Description |
| -------------------------------------------------------------------- | ------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------- |
| <a id="COM_FLTT_LOW_ACT"></a> Low flight time for safe return action | [COM_FLTT_LOW_ACT](../advanced_config/parameter_reference.md#COM_FLTT_LOW_ACT) | Action when return mode can only just reach safety with remaining battery. `0`: None (default), `1`: Warning, `3`: Return mode. |
| <a id="COM_FLT_TIME_MAX"></a> Maximum flight time failsafe level | [COM_FLT_TIME_MAX](../advanced_config/parameter_reference.md#COM_FLT_TIME_MAX) | Maximum allowed flight time before Return mode will be engaged, in seconds. `-1`: Disabled (default). |
| Setting | Parameter | Description |
| ---------------------------------------------------------------- | ------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------- |
| <a id="COM_FLT_TIME_MAX"></a> Maximum flight time failsafe level | [COM_FLT_TIME_MAX](../advanced_config/parameter_reference.md#COM_FLT_TIME_MAX) | Maximum allowed flight time before Return mode will be engaged, in seconds. `-1`: Disabled (default). |
## Manual Control Loss Failsafe