• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

When to use a separate receiver battery on an electric plane...


Flying Derp
What's everyone's take on this? I guess the options here are:

  1. use the ESC's built in BEC
  2. Use an OPTO ESC and a separate BEC
  3. use an OPTO ESC and a separate receiver battery

So far on my electric planes I've only used the BEC that's built into my ECS's. Mainly b/c until now my largest electric has a 63" span and flies on 4s with only four servos. I'm now building an 8ft. Senior Telemaster that's going to be electric, that's why I ask. I think most people follow a rough guideline like this... use the ESC's BEC for smaller planes, park fliers, etc. and for, say .60 and larger size planes, use a separate BEC or an rx battery.

I have a 80a 5v ESC for the Telemaster so it can handle the five analog servos I'm going to use but most likely b/c of the size of the plane (safety reasons) and the expense of a larger plane I'll probably go with a dedicated rx battery that way if the ESC fries, I can still have control of the plane.

Here's a couple photos of ESC failures just this week at one of the local clubs.

esc failure1.jpg

esc failure2.jpg

Chime in people!

Ak Flyer

Fly the wings off
For a large plane, I personally prefer the security of a separate battery, especially a high lift model that won't mind the extra weight.


Old age member
I think that you forgot the "old" way with a receiver battery without any BEC at all to worry about.
I myself would not worry with only 5 analog "normal" servos on a plane with 5A BEC.
but i am always using the rx battery diode indicator on my planes. There should newer light up any diodes more than the highest green when "running wild" with the sticks on the TX.
Frying an ESC does not automatically mean that the built in BEC will die. I have landed the few times i have fried the ESC witout any problems. Using a separate BEC is not much more safe if the separate BEC is not much more powerful and has a good cooling.


Propaganda machine
I've never used a seperate battery to power the rx. I use a seperate UBEC for planes with a lot of servos (5 or more), for FPV and with models with a high amp draw. A UBEC keeps the ESC much cooler than using the built in one and is guaranteed not to burn with the ESC if it does die.

You'd have to have some pretty serious kit on board to need a seperate battery.
If the plane is big or you have lots of FPV gear I would use a separate power source.

I already do have separated the video-LIPO from the Motor LIPO and the power comes from a separate UBEC to ease off the ESC that needs to worry about other stuff.

If you have many servos and still want to be able to save your plane in case of ESC/Motor-failure you could still control your plane if you have a separate LIPO/UBEC for the servos and receiver (the extra UBEC-LIPO is needed if the ESC kills your main-LIPO)

My current FPV plane are Bixler 1 & 2 (the Skywalker is obsolete)
I have prepared the wirings for separate LIPOS but I did not yet included an UBEC - but it is lying on the desk for next soldering session.