i power my pixhawk with a power module. Now I would change on APM 2.6 for a test. May I use the power module from pixhawk or do I have to power the APM by ESC or BEC?
The genuine 3DR Power Module will work with either the Pixhawk or the APM2.x flight controllers.
If you are using clone versions, there could be issues and I would check with the reseller you bought the flight controllers from.