4ld: the BEC circuit

luca 07/11/2014 4

ESCs usually contain a circuit named BEC (Battery Eliminator Circuit), that is a circuit that outputs a regulated voltage of 5V, used for example to power the receiver. The circuit is defined “battery eliminator” because it allows to use the “main” battery – connected to the ESC – without the need of a dedicated battery.

On the market there are some ESCs, named OPTO, that don’t contain the BEC circuit because of they are designed to be used on multicopters.

If you open an ESC or have an ESC with a transparent cover, you can notice the voltage regulators of the BEC circuit:


In a multicopter, the receiver is connected to the flight control board, and the control board also powers it. ESCs are connected to the flight control board too but the control board has normally a dedicated power supply. This is the reason why it is suggested to avoid that the ESCs power the board through their BECs.

The activity is very simple: you have only to unthread the red wire contact from the ESC connector (you may also cut it, but this solution is reversible):

using a small screwdriver, lift the plastic tab that blocks the contact and unthread it:

bec-1 bec-2

use now an insulating tape to secure the contact:

bec-3 bec-4

After having modified all the four connectors of my ESCs, I reconnected them to the Naza:



  1. Silvano 06/03/2015 at 16:59 - Reply

    Gentile Luca, questa operazione sugli ESC va fatta con qualsiasi FCB? Grazie

    • luca 06/03/2015 at 17:23 - Reply

      Ciao Silvano, se la FCB ha un suo alimentatore esterno sì, se invece viene alimentata dagli ESC, va lasciato il cavo rosso solo ad un ESC su 4, che sarà quello che fornirà l’alimentazione alla FCB.

  2. Silvano 09/03/2015 at 21:00 - Reply

    Avrai capito che sono un super neofita, la scheda deve arrivarmi. È una hobbyking kk2.1 hc . Penso sia valida la seconda opzione. Cosa ne pensi? Grazie

    • luca 11/03/2015 at 20:16 - Reply

      Ciao! Sì devi lasciare un solo cavo rosso per alimentare quella FCB

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