AP_BattMonitor: Add the battery critical action delay time

[muramura]

The battery failsafe includes both a warning and a critical stage.

Each stage has its own action settings. There is a duration during which the voltage is continuously monitored before the action is taken. For example, due to motor load, the battery voltage can drop to the critical level.

Currently, the duration for both the warning and the critical voltage levels is the same. If the voltage drops below the critical level, the drone may lose thrust.

By setting different durations for the warning and critical stages, appropriate actions can be taken.

BATT_CRT_TIMER set 0

BAT_CRT_TIMER set 1000

[IamPete1]

I don't understand why you would want a different time for each in the real world?

[muramura]

@IamPete1 san.
There are times when the voltage drops suddenly—for example, due to poor contact in the battery connector. In such cases, the FC (Flight Controller) may not be able to execute emergency actions within the same time frame as warnings.

I believe it's acceptable for the durations of warnings and emergencies to be separate.