Built in BEC VS. External BEC? - RC Groups
Thread Tools
Jul 28, 2012, 06:20 PM
Registered User

Built in BEC VS. External BEC?

So I'm wondering if there are any advantages with using an external BEC vs. one built into the ESC.

Also Built in and External BEC's interchangeable?

I ask because i just purchased a new EDF jet and my receiver doesn't have a set of BATT pins for an external BEC.
Sign up now
to remove ads between posts
Jul 28, 2012, 07:15 PM
I live my life 12oz at a time
arnav's Avatar
External BEC is better. If your ESC burns down, it will most likely take the internal BEC with it (and you know what that means). With an external BEC you remove any dependency on the ESC. In addition, most internal BECs are only rated for 3A. If you are using 4S and above, or if your servos are drawing more than 3A (or whatever the internal BEC is rated for) you would need an external BEC anyway. For the $10 to $25 that they cost, it is well worth the insurance "policy".

Yes, they are interchangeable in a sense that you could one day use the internal ESC's BEC and another connect the external BEC (tough I am not sure why you would want to do that). If you are using an external BEC and an ESC with an internal BEC keep in mind you need to disconnect the middle wire on the ESC plug which connect to the Rx (or else you will fry the Rx). If you haven't bought your ESC yet, and you know you will be using an external BEC, you may opt to get an ESC without a built in BEC altogether (sometimes designated as -opto),

The external BEC can connect to any unused port on your Rx.
Jul 28, 2012, 10:37 PM
Registered User
Wintr's Avatar
If you're not using all the channels of your receiver, you do have a set of BATT pins for an external BEC, since the + and - pins are shared across all the servo channels.

Some ESCs will have a switch mode BEC, which aren't affected as much by battery voltage as the standard linear type. It's the switch mode type you want when you look for an external BEC, too; as some are linear. With a linear BEC, the higher the battery voltage, the less current it can supply, and at 3S or higher voltages, the rated current has to be reduced. Also, it's rare to be able to connect more than one BEC without problems.
Jul 28, 2012, 10:43 PM
Dude, I do fly all day long!
rcalldaylong's Avatar
You don't need an extra channel to use an external BEC

And yes, an external BEC saved one of my beloved plane many years ago when I was a newbie and didn't have an ampmeter. The ESC got so hot it fried itself and completely burned up, but the external BEC kept ticking and i was able to land safely.

External UBEC "How To" (5 min 27 sec)
Jul 29, 2012, 12:29 AM
Registered User
You guys totally rock! thanks a million for all the great info and advice! my new jet is up and running!!! Here is my build thread if anybody is interested.

Build Thead F-16 - EDF - FPV

Thanks Again!!!
Jul 29, 2012, 02:56 PM
Registered User
Just curious, could you use the bind/data pins for the external BEC?
Jul 29, 2012, 03:01 PM
Registered User
Wintr's Avatar
Originally Posted by sykmethodz
Just curious, could you use the bind/data pins for the external BEC?
That's basically what they are there for - mine are labeled bind/batt.
Jul 30, 2012, 09:18 AM
Registered User
For an expensive plane that runs 4 (or more) regular size servos, always go with an external BEC. This will guarantee your RX power.

And don't put crappy batteries on the external BEC! Use a voltage meter, and check to see that your batteries have good cells.
Jul 30, 2012, 05:20 PM
Registered User
Awesome! Thanks guys super helpful. Saved me a hundred bucks!
Dec 06, 2016, 09:49 PM
Registered User
Hi guys yeah i just bought the 1100mm T-28 Trojan and i am thinking of installing a ubec in it just for insurance

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Adding external failsafe to 2.4 radio w/ built in failsafe. rcbif DIY Electronics 0 Jul 23, 2012 02:23 PM
For Sale Mystery 20A Brushless ESC with Built-in BEC for RC Plane/ Helicopter (Yellow) Aiden6 Aircraft - Electric - Power Systems (FS/W) 0 Jul 16, 2012 11:20 PM
Question Rx Pack vs. External BEC knlken Power Systems 5 Apr 23, 2010 07:06 AM
Discussion Basics of BEC's External vs. ESC based? Education needed please! Valid8r DIY Electronics 9 Feb 10, 2009 03:44 PM
Discussion External BEC vs "built-in" with ESC BadClams Foamy EDFs 9 Jan 05, 2009 02:42 PM