Originally Posted by Wrongway-Feldman
For the most part I wire the bec in to the power plug on the esc that connects to the battery.
You just tap the BEC power supply wires into the ESC input cables, usually soldering them in at the Deans connector (or whatever connector you use). This would be the same regardless of what ESC you are using. You would generally only power the BEC off a seperate battery in high voltage installations where the main flight battery was too high voltage for the BEC to handle.
If the ESC has a built in BEC you must also disconnect the red wire from the plug that goes to the receiver. If the ESC is 'OPTO' (i.e. no BEC) then leave the red wire connected.
As to if you need a seperate BEC or not; that wasnt the question asked so i wont speculate on an answer