1) Some technical background
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The thresholds for battery-related actions are defined with following parameters:
BAT_CRIT_THR (FLOAT) | Critical threshold
Comment: Sets the threshold when the battery will be reported as critically low. This has to be lower than the low threshold. This threshold commonly will trigger RTL.
Reboot required: true | 0.05 > 0.25 (0.01) | 0.07 | norm |
BAT_EMERGEN_THR (FLOAT) | Emergency threshold
Comment: Sets the threshold when the battery will be reported as dangerously low. This has to be lower than the critical threshold. This threshold commonly will trigger landing.
Reboot required: true | 0.03 > 0.1 (0.01) | 0.05 | norm |
BAT_LOW_THR (FLOAT) | Low threshold
Comment: Sets the threshold when the battery will be reported as low. This has to be higher than the critical threshold.
Reboot required: true | 0.12 > 0.5 (0.01) | 0.15 | norm |
What should happen is defined with parameter
COM_LOW_BAT_ACT (INT32) | Battery failsafe mode
Comment: Action the system takes at critical battery. See also BAT_CRIT_THR and BAT_EMERGEN_THR for definition of battery states.
Values:
- 0: Warning
- 2: Land mode
- 3: Return at critical level, land at emergency level
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COM_LOW_BAT_ACT=3 should be there.
Parameter reference:
dev.px4.io
2) Typhoon H Plus
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H Plus is based on PX4 Autopilot but customized for Yuneec needs. Most of the parameters are read-only due to security reasons. I don't know which one. Due to customized handling, changes in parameter
may have unexpected effects. Whatever you do, do it on your own risk.
I do not have a H Plus (at least a working mainboard which would be enough to do testing). That's why I start here speculating. May be it is possible to access the some of the parameter with QGroundControl. However, reading the parameters is possible.
If you can access parameters with QGC, from my experiences with Typhoon H and PX4 firmware (aka Thunderbird) the Critical battery threshold should not be below 10% (=0.10) to have enough capacity for RTH. The minimum setting 5% is dangerous. Your idea with 15% sound reasonable.
Important remark: If you use QGC, never do a firmware update using QGroundControl. This may brick the H Plus.
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