Redundant Power Pixhawk / Battery Elimination Circuilt (BEC)

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1

Hello,

I see that the Pixhawk can support up to three in flight power / redundancy options. So one output from the ESC to the output rail, then if that fails the power module will take over (ok other way around). Plus a third method by using some kind of splitter for the rail power (not really looked into that)

I am not sure I follow the logic in the power redundancy suggestions for the Pixhawk. I get that the power module (which should the be primary source of power for the Pixhawk as I understand it) will stop power spikes from digital servos (which would cause the Pixhawk to reboot mid flight). However, if the primary power source fails, ie the power module, then the ESC will not take over, because it too takes its power from the Power Module.

Many Thanks

Stuart

3

Hi Stuart

Yes I totally agree with you, I think that when you read about a triple redundant power supply its mainly just ‘marketing talk’ as the third one is USB power which isnt exactly that usefull in when flying :stuck_out_tongue:. 90% of multicopter pilots power the motors, and flight controller from the same power source so if one goes out its most likely that the other will not have power too. But should you power your pixhawk from its own battery and your motors from another then you can have dual redundancy power supply, but then again if your ESC looses power, so will your motors so there is not much point in having a functional flight controller on a multicopter if you dont have any motors as its just a falling brick at that point. The only time this would be useful if you are using a backup system such as a parachute recover system so that if your motors cut out your flight controller will still have power to deploy the chute.

4

Hello,

Okay, so as I thought, doesn’t make a huge amount of sense. Thanks for clarifying.

The main power source has XT60 connectors, and as I mentioned in another post, I am going to change that to Deans. Meantime though, I am powering the Pixhawk from servo rail output pins, and USB during the calibration process (using APM 2.0). The calibration process isn’t working (another post)

Is there a problem with not powering using the main power port?

Thank you

5

Although its usualy not a problem to power pixhawk via ESC, I suggest that you always use the power module as it provides a clean power supply to your pixhawk and also allows you to monitor the battery level. When you are performing the initial configuration it should be fine to just use the USB cable as it provides enough power for the pixhawk. And then you can connect the battery when performing the ESC calibration.