BEC and 7,4v RX

[Sunburn]

Hi everybody , I'm newbie
I have a question about BEC....
I ve seen the Harley's diagram that shows 2 ways to bind BEC and servo to RX
The first is the most simple and that's what I used, having a RX Futaba R304SB that run at 7.4v: BEC goes directly into bus port of RX
The other diagram shows the binding from servo to RX with yellow signal wire only (BEC gives the power directly to servo) even though the RX is 7,4 v in this case as well.
Is there any difference assuming that's 7.4v RX in both ways?
I have a doubt on that because my servo hitech ....seems doesn't pull as expected ( I might hold it pretty easy)
Thanks!

Castle Creation BEC 10 Amp +MMP




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[Odd-M]

If you're running BEC on servo only, the Rx will get power from the ESC. For the most this is 6V, which is enough. Rated at 7,4V means that it'll tolerate this as a maximum. You could probably run it as low as 4,8V.

This method takes some cutting and soldering, or you could make a RX bypass. I just use the easier BEC to Rx, unplugging red wire from the ESC connector.

 

[TacoCrawler]

7.4v is 7.4v

It is generally safer and more efficient to wire the BEC power directly to the servo,
then utilize the ESC's internal BEC to power the RX.
^ (more common to be 4.8 - 5.0v)

I have my BEC pushing 7.4v thru my Axial AR3 RX
and it has held up to that voltage.
But some RX's may not hold up to higher voltage input.

ie:

I purchased a Fly Sky GT3-C TX/RX
and that came with the GR3-F RX
and with the BEC pushing 6v thru it, failure occurred.

note:
The FS GR3-F RX has been replaced/upgraded
to the FS GR3-E RX which is claimed to handle 8v.

Since the Axial "AX" series TX/RX are compatible with FS TX/RX systems.
I replaced the failed FS GR3-F RX with my original RTR Axial AR3 RX...
And it has handled 7.4v running thru it for nearly a year.

note:
Wiring the BEC's power thru the RX
requires that the ESC's power wire be removed and taped off(secured).

Sooo...

If you know your RX will handle the 7.4 voltage that you choose to utilize
you'll be fine running the BEC thru the RX.

But if you're not sure...
it's better to be safe, then sorry
and run the power from the BEC directly to the servo.

note:
If you do wire the BEC power directly to the servo...
The ESC's internal BEC power wire must remain
so that it will power the RX.

 

[Solitaire]

As said above, it's always better to power the servo directly from the external BEC and power the Rx with the ESC's BEC. It's not the voltage that's the issue (whatever the Rx is rated at), it's the amp draw of a servo when you're running everything through the Rx. The small traces on the PCB in the Rx are not designed for high amp draws.

 

[GodSpeed999]

As said above, it's always better to power the servo directly from the external BEC and power the Rx with the ESC's BEC...

And this makes it easy and neat -- Holmes Hobbies LLC RX Bypass Adapter

 

[Sunburn]

Thanks to all! I changed my rig after these topics
Binded servo to BEC and RX with ESC! ...I didn't consider about amp drawing!


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