Tag Archives: BEC

Is ESC without BEC an OPTO ESC – some quick explanation

I will try to keep it super simple (KISS) and explain why an ESC without BEC is not necessary an OPTO ESC. BEC stays for battery eliminator circuit. It is an electronic circuit, which delivers power to other electronics, like your flight controller or receiver. That is why we connect the red wire of the servo cable to the FC, it simply outputs (hopefully stable) 5V.

Some ESCs don’t have an integrated BEC and can not supply power for your controller or receiver (for example: KISS ESCs, Afro Race Mini 20A or XRotor 15A). In this case you need a separate BEC for powering them. There are also power distribution boards with integrated BEC. I personally use the ACSP3 from Nick Arsov.

So far so good. The problem is many ESCs retailers and manufactures (mostly Chinese) don’t know, that an OPTO ESCs is just not equal to ESC without BEC. OPTO means that the ESC have an opto-isolator. If you Google it, you will find that, it is a optical component that transfers the signals between two isolated circuits by using light. The main purpose is to prevent rapidly changing voltages or high voltages on one side of a circuit from distorting transmissions or damaging components, like the receiver, on the other side of the circuit.

I have never experienced any problems with my not OPTO isolated ESCs, but thought it is good to know what an OPTO ESCs really means.

How many amps (A) draw a flight controller and/or a receiver

Today I saw a question on the hobbyking.com if the BEC of an Afro 30A ESC could power the famous KK 2.1.5 flight controller and a receiver. The BEC of the Afro ESC is rated for 0.5A. But on the Hobbyking site there was no information how many amps the KK 2.1.5 and a connected to it receiver draw. So I take my Turnigy Watt Meter and measured the current to my KK board, receiver and my HK Multiwii and Megapirate flight controller. Here are the results:

KK 2.1.5 / KK2.0 board 100mA = 0.1A
HK Multiwii Megapirate AIO 100mA = 0.1A
HK Multiwii Megapirate AIO with Ublox GPS 180mA = 0.18A
FrSky 8CH 2.4G Receiver 100mA = 0.1A


The answer of the question: Yes the integrated BEC of the Afro 30A ESC can power the KK board (or the HK Multiwii AIO board) and a receiver, as both draw 0.2A.