BEC vs. UBEC.....whats the difference? - RC Groups
Thread Tools
Sep 28, 2009, 07:37 AM
Flyin' Texas

BEC vs. UBEC.....whats the difference?

I am wanting to know the difference between a BEC and a UBEC ?

what do they stand for? what exactly are they?

I have somewhat of an idea but not sure.

thinking about buying one of these

and need to know what I need to power my FM receiver. anyone have a recommendation from hobby king?
Sign up now
to remove ads between posts
Sep 28, 2009, 08:16 AM
Registered User
Dr Kiwi's Avatar
A BEC (battery eliminator circuit) is typically built into the ESC (electronic speed control) and by modifying the voltage from your flight battery (typically 2s -7.4v or 3s 11.1v) delivers power for your Rx and servos at ~5v (but usually no more than 2A-3A).

If you go to 4s (14.4v) or more, and have more than 3-4 servos, the usual linear BEC in the ESC cannot cope with reducing the high voltage down to the ~5v the Rx and servos need, nor can it deliver enough current to power many, especially digital, servos.

Then you need a stand alone UBEC (Universal BEC) which is typically a switch mode unit which is capable of reducing the voltage from 4s+ packs to the required ~5v, and can deliver as much as 10A to power many, big, digital servos and your Rx.

That ESC you link to is an Opto, so it has no built-in BEC... you will have to use a UBEC or carry an additional battery pack (4.8v-6v) as a power source for your Rx and servos.
Sep 28, 2009, 08:22 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Search for threads with 'bec' and 'ubec' in the title.
Sep 28, 2009, 09:39 AM
jackerbes's Avatar
Read the reviews on that ESC, it does not look like it is getting very favorable reports at all. I would not buy it.

Also, in one place it says it has no BEC, in another it says the BEC is an OPTO. But one of the reviewers reports that "Terrible soldering on the servo wire, the wires were stripped too far back from the point they are soldered, give it a good twist and it will short out the 5v system." That implies that there is 5V on the BEC connector and as I understand OPTO ESCs I did not think 5V would be there. Best to check or cut the wire in any case.

All in all, a very confusing mess there. Welcome to Hobby King, throw it away if it is miss-described or does not work well. Standard 30 feet or 30 second warranty applies.

To the general question, I think the term UBEC always implies that it is an external switching mode BEC but the terms and specs are not used in a standardized manner.

There are devices called BEC and UBEC that are both external battery eliminators that are not built in to a ESC.

And it is generally true that the BEC circuits built in to an ESC are linear mode devices and UBEC's are switching mode devices.

But you really need to make sure which one you have or are buying if your goal is to have the better switching mode instead of the more problematic linear mode type BEC. Like a lot of things in RC, you have to study the words and numbers a little (types, input voltages, output voltages, ratings, etc.) to make sure you get what you need.

And like anything that comes from China and is cheap, I would downrate the output capacity to 75% or so of what they advertise.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question spectrum dx6 vs dx6i?? whats the difference?? for parkflyers? hamcigar Radios 6 Feb 27, 2008 04:02 PM
Turbo vs pico servos, whats the difference? wolfance Parkflyers 0 Jun 10, 2003 08:01 PM
Astroflight 805 VS. 806SP. Whats the difference? Mike C Power Systems 1 Dec 08, 2002 10:23 PM
Sanyo 500 vs 600 Whats the real difference? duworm Electric Sailplanes 1 Mar 04, 2002 05:16 PM
Whats the difference A300/25/A3 vs A300/25/A4? Inverted-3D Electric Heli Talk 1 Oct 16, 2001 07:05 AM