Originally Posted by ron_van_sommeren

Or feed power from two switching SBECs. If manufacturer says so, you are safe to combine linear LBECs. ...

Sloppy writing Ron

It should be

Nor feed power from two switching SBECs.
However, if manufacturer says so, you are safe to combine linear LBECs.

I already correct my original message.

Vriendelijke groeten, en wees voorzichtig, Ron
• Without a watt-meter you are in the dark ... until something starts to glow •
• e-flight calculators • watt-meters • high power motor tips&tricks • Cumulus MFC •

(UBEC is a propriatery brand name, informationless acronym, I prefer L-BEC, linear, and switching S-BEC, switching, those two acronyms contain more info.)

Four anything above 3s use a switching SBEC, not a linear LBEC. An LBEC, if it could handle the voltage at all, would have to dissipate way too much power (P = ((Vbatt -Vservos) × Iservos)) and would get very hot and/or shut down, temperorarily, preferably during in the air. It will work fine again once it has cooled down.

The higher the power-pack voltage, the fewer servos a non-switching = linear LBEC can handle. Switching SBEC's hardly have this restriction.

The higher the battery voltage, the hotter a linear LBEC will get, for a given current/load/servos.
Or, in other words ...
The higher the battery voltage, the lower the current a linear LBEC can supply.

In depth:

• About BECs, number of servos and battery voltage
• Digital servo's and BECs!!!
• OPTO ESC Receiver Input Voltage???
• Linear BEC current rating
• L-BEC & S-BEC calculator
• System wiring

All about BECs for RC model planes (24 min 58 sec)

Vriendelijke groeten, en wees voorzichtig Ron
• Without a watt-meter you are in the dark ... until something starts to glow •
• e-flight calculators • watt-meters • high power motor tips&tricks • Cumulus MFC •

Originally Posted by Renegadeflyer

Why is that better than what Judge says above?

Using the BEC + a 40 gram Pulse Defender or Scorpion BUG is a lighter solution and doesn't require charging of a RX pack while providing rx power redundancy if the ESC/BEC fails. The Pulse self charges off the BEC and the BUG rarely needs recharged. Edit: agree with Judge below, not better, just a different option.

Originally Posted by Renegadeflyer

Why is that better than what Judge says above?

Personally I don't think it is "better", just a different solution. I prefer not to add extra stuff to a plane/heli. I use the same approach for powering the radio regardless of what provides the motive force for the aircraft. engine versus electric motor. Charging RX packs has been a part of flying for me for decades, not that big of a deal. And on my elcetrics I am already charging the motor packs so charging the RX pack is easy.

Has anyone ever really tried using the BEC and RX battery? I've been doing it for well over a year now. receiver only sees 7.4-8.2v and the output is the same. my battery will "charge" off the BEC. It just basically never drops below 3.9ish volts per cell. Which is plenty of power to get the plane to the ground at least. Been doing it this way for quite some time on multiple planes. Mainly Talon 90s

Originally Posted by Judge

Yes. But NEVER feed power from BOTH the RX pack AND the ESC/BEC

This Buffer makes it so you can use a BEC and a battery ; for
redundant power to radio and servos :

https://western-robotics.com/rc_model_electronics/bbfr/

Anyone ever try this devise ?

Bille