Hi
I have recently started working on a quadcopter. I was fascinated with the concept of power switching and wanted to implement the same in my Quad.
Conditions I want to implement:
The autopilot must use the secondary source for takeoff and landing (by landing, I mean RTL).
During operation, it must always use the primary power source and should never switch back to the secondary source unless RTL is triggered.
There must not be any affect even if the autopilot detects any pilot input, i.e., if the pilot switches back to hover in between the operations, the autopilot must override the command and keep operating on the primary power source.
Is it anyway possible to do such a thing, and one more thing I want to ask?
If the autopilot switches between the power sources, then there are high chances that autopilot starts rebooting and this will crash my copter, so what are the possibilities to implement the above-mentioned point and still my copter stays airborne?
You can use two batteries and ideal diodes or mosfet switching. Problems can arise because the ESCs try to give back power to the battery as the motors are slowed or braked. If there’s diodes then the voltage can rise excessively and ESCs can shut down due to over voltage or even be damaged.
And that’s another part to fail.
There are power management boards that will isolate a faulty battery and continue on with the other, but that is still added weight, complexity and cost. You would probably only use that system for copters specifically designed for high reliability like flying over people.
You are better off just having one big battery, or two in parallel, of the correct capacity. It doesnt make any sense for a multirotor to carry around a battery that’s it’s not actively using - every gram affects flight time. You will notice that no one uses an extra battery just for some accessory or the receiver or flight controller, and everything runs off the main flight battery.
EDIT
A VTOL is different - forward flight has very different battery requirements and load compared to vertical flight. So it makes sense to use two different batteries in that case.