Understanding BEC in FPV Drone Flight Controllers and ESC

by Oscar

In this article, we’ll delve into the roles and benefits of BEC in FPV drone flight controllers and ESC, with a focus on the advantages of using a BEC, and the differences between linear and switching BECs.

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If you’re selecting an ESC for your FPV drone, you might find this accompanying post helpful: https://oscarliang.com/esc/

What is a BEC?

A Battery Elimination Circuit (BEC) is essentially a voltage regulator that steps down the voltage from the main LiPo battery pack (e.g., from 4S 14.8V or 6S 22.2V) to a lower voltage like 5V or 9V. Commonly integrated within the flight controller or ESC, the BEC eliminates the need for a separate battery to power your electronics.

Further Reading: What does “S” mean in “2S, 3S, 4S and 6S batteries”?

A “UBEC” stands for Universal or Ultimate BEC. It’s used when an ESC doesn’t have a built-in BEC, or when a standalone power system is needed. Known for their efficiency and reliability, UBECs can also provide higher currents than typical BECs. They connect directly to the main battery, much like an ESC.


Why Opt for a UBEC Over an ESC’s Built-In BEC?

Choosing a UBEC over a built-in BEC in your ESC offers several benefits:

  • UBECs are more power-efficient.
  • Unlike BECs, UBECs don’t overheat under high voltage differences or loads, enhancing their reliability.
  • UBECs typically support higher current outputs safely.

These advantages are due to the different methods each system uses to regulate voltage. Most integrated BECs are linear, while UBECs use a switching method.

If your ESC lacks a BEC, an external UBEC can be used to power your electronics. Simply connect the UBEC’s input cable to the LiPo battery and its output to your receiver and flight controller, without altering the ESC connection.

However, if you’re integrating a UBEC in a setup where your ESCs already have built-in BECs, you’ll need to disable those by disconnecting the red wire (5V) from the ESC’s servo lead.

Linear BEC vs. Switching BEC

BECs can be either linear or switching. Linear BECs, often found in ESCs, dissipate excess voltage as heat to step down the LiPo voltage to 5V. This is not particularly efficient, especially at higher voltages or with significant current draws, as it can lead to wasted power and overheating: https://oscarliang.com/linear-regulator-vs-switching-regulator/)

Linear BEC VS Switching BEC

Switching BECs, on the other hand, toggle the power supply on and off to manage voltage reduction, avoiding the overheating issue common with linear BECs. They maintain about 85% efficiency across higher voltages and currents, making them preferable for setups above 4S.

From personal experience, I’ve run a 4S setup on my Blue series ESC with its built-in BEC to power my flight controller and receiver without any issues, though the ESC does get warm. Proper airflow is essential in such configurations.


Whether you choose a UBEC, a BEC, or an ESC with an integrated BEC, understanding these components’ functions and limitations is crucial for developing a reliable and efficient power system for your drone.

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Paul Blase 9th June 2021 - 1:47 am

You might want to define “S”, as in 3s. Not exactly electrical standard terminology.

Paul Lowkater 15th October 2021 - 3:37 pm

You might want to do your research before you talk correct someone. S is a comon term when dealing with Lipos. ?

Hugh Davis 7th February 2020 - 6:22 pm

Hey everyone.
Oscar I have seen one of your videos on YouTube and when I did I search on Google about UBEC’s I saw you had an article about them so hear I am. Great info but I’m new to all of this and it can be confusing. I have a project ahead of me and I’m building a very light foam racer RC plane. I’m using the Geprc 2306.5 2450kv motor with a 6×4.5 carbon fiber GF prop. This motor is advertised at 2300g thrust at 100% throttle. My plane should weight about 800-900g all up weight. I want the most power from my battery going to the motor w/o waisting it into heat. I want this plane to be fast. Can you or anyone here suggest a setup for me? I have two versions of this plane one version has lots of extra room in the fuselage and the other I have narrowed it to reduce frontal area and drag. I’m not looking for a lot of flight time but I am looking for the best reliable setup. and I’m honestly having a hard time picturing the wiring in my head and how everything should connect. I know they are diagrams on Pinterest that explain pretty much everything so maybe I’ll look there but in the meantime could someone suggest a UBEC setup. Thanks a lot. Or even a better motor…but for the power/weight ratio the on I’m looking at seems to be the best…so far. Ok, thanks in advance for any information.
Columbia SC

RAYMOND CARON 23rd November 2019 - 3:31 am


Gerry van Grevenhf 18th April 2018 - 11:48 pm

Hi to al

This is my first time dealing with a rc airplane radio trans mitter system
Here are my questions
I have a bec (esc) 30 amp which I bought with a A2212 brushless motor and bought a separate ubec. 20 amp.
Now I am stuck, they look exactly the same, they have the same amount of wires. Every schematic I have seen does not fit my wiring.

Q: is there a speed control included in ubec device?
Q: can I install a pn ubec with a bec ( esc) system?
Please help me out if that is possible

Gerry van Grevenhof
Gvang0608 gmail.com
Thank in advance

Gus 4th March 2018 - 8:54 am

Best article I have read on the matter. I actually understand now. I have a 40amp esc with a bec 3-5v and a Air3 Inav which came with a UBEC. So just to clarify as this will bw in a plane and the ESC has a large heat sink on it and will be mounted outside the plane to keep cool it should be fine to power the inav without the hassle of soldering on the UBEC then? It also cam with a capacitor so having that plugged in will also help?

Or have I Totally misread the article. Using 3s batteries.

Thanks in advance.

Alexandros 11th September 2017 - 2:32 pm

Hi i want to use a 4 in 1 esc (without bec ) i have to buy Ubec or bec and connect it or i can fly my project without bec, ubec ? thanks Alex

Oscar 18th September 2017 - 4:05 am

BEC and UBEC are a way to provide power to your other components such as FC and RX, if you can find power elsewhere then you don’t need UBEC/BEC.

Narmadha M 15th December 2016 - 10:07 am

Can I connect a 5V battery directly to ESC .Will it run the BLDC motor without problems?

vern 27th September 2016 - 8:09 pm

can i power the fc and rc w/ one esc bec and use the other 3 esc bec to power leds, fpv system, etc that use 5v?

Oscar 3rd October 2016 - 3:57 pm

yes that should work :)

JonDrones 23rd August 2016 - 2:15 am

Here’s setup. 4s battery, seriously pro f3, little bee 20a option esc’s. Now my 5-1 power hub has bec 12v and bec 5v. My battery leads solder on the VCC inputs, could I use one of the bec outputs either 5v or 12v to accomplish what’s needed for the esc’s to operate correctly? Option newb

Oscar 26th August 2016 - 2:49 pm

Yes you can, as long as the voltage and current rating meets the requirement.

Adam U. 1st August 2016 - 4:53 am

Hi! I’d like to build my rc quad on 210 BeeRotor frame. It’s a cool PDB board with 5v 12v outputs! :) then I’d like to connect my opto mini 20a esc so I need Ubec? I Think no. I connect esc directly to 5v outputs on PDB end to FController. It’s good?! Ghanie for answer. BR

LV Chong 11th April 2016 - 6:42 am

Hi Oscar,

Good blog !!, thanks for sharing.
I also have a quadcopter..
i use a 4s batt to power the motor and esc (emax esc with bec)
I also put in a 2s batt to power up my tx, gimbal & camera (gimbal pit roll control also have red wiire to FC)
when i connect anyone of the battery, the FC will lights up and working.
if i connect 2 of them, you think it will overload the FC? my FC is APM2.6.
also, does the 600mw fpv tx, 2d gimbals & camera consume battery?
the reason i put in extra 2s battery is to get longer fly time.

Thank you.
LV Chong

Nate 19th February 2016 - 2:50 am

I have a 5 volt soldering port on my PDB. Can I use it for both my 5v flight controller input and my 5v CMOS camera?

Oscar 22nd February 2016 - 11:30 am

yes that should be fine, just make sure it can provide enough current for your devices.
by the way, I recommend joining this forum, it’s very useful and there are lots of helpful people there. I am a daily user too :) http://intoFPV.com

Tom 3rd August 2015 - 6:15 am

I currently have one motor with BEC connected to FC and all others are without bec, would this cause any problems?

BTW I love your blog I have used many times you are a star for this :-)

Oscar 6th August 2015 - 12:37 am

no that’s absolutely fine, just make sure you are connecting the Ground with ESC signal as well! Otherwise you could potentially have ESC sync issue.

Simon 18th June 2015 - 1:29 pm

Where do you put a UBEC if you have opto esc. Between the ESCs and the Flight Controller? Or between the Battery and the Flight Controller?

Oscar 19th June 2015 - 1:02 pm

just between battery and FC… basically it’s like connecting 5 ESC, but the UBEC isn’t connected to any motor :)