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BEC this BEC that rx question

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  • BEC this BEC that rx question

    Good day everyone,

    Got a quick question about BECs, the more I read about it, the more confused I get.

    Isnt it the ESC purpose to regulate power to electronics?

    How do I know if my ESC will not toast any other components?

    I have used for years escs on rc cars (not nitro of course) and never had to install a bec. Never had to on any of the large scales, which use large servos, but the receiver is basically the same as other platforms.

  • #2
    BEC= Battery Eliminator Circuit.

    Early ESCs did not have any means of providing power to the RX, they just controlled the motor.

    Someone got the bright idea of tapping into the power of the battery used to power the motor (these were RC cars that had it first) to also power the RX. At first they used a simple linear (resistor based) regulator.

    Next someone started incorporating the regulator into the ESC and they called it the BEC. (appx 1980 to 1985)

    For a while. Futaba made Receivers with the BEC built in for RC cars. this was before the BEC was commonly part of the ESC.

    Then they began using "switching" regulators in the stand alone BEC's and the ones incorporated into the ESCs. These are much more efficient and can provide more power to the RX and servos.

    Many ESCs still do not have a BEC built in. In many quadcopters you get a set of 4 ESCs with only one having the BEC. High voltage ESCs (rated for more than 4S LiPO)almost never had BEC circuits built in until recently. Its still more common for 6S and above rated ESCs to not have the BEC built in.

    I normally will use a separate RX battery for anything using 6S or more even if there's a BEC built into the ESC.
    FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.

    current planes from 1/2 oz to 22 lbs


    • #3
      Understood, and thank you for the explanation. I have read online lots of stuff about the topic, but you covered areaa that had not been mentioned on any sites so far.

      It caught my attention because have read on brushless glider and parkflyer threads about using BEC. And to me it does not add up cause for years I have used the power from the lipo up to 5S and never had the need for a receiver pack.

      Possibly more hype than it should be, and once its been installed nobody wants to admit its useless.

      Every so often I only use 6S, and for now, on a 1/8tg rc truggy, the esc is rated at 185A. I got a few rx bats floating around which I can use to be safe and protect the rx. Its a rc car, not that I will have dead sticks anytime soon.


      • #5
        I learned my lesson about BECs the hard way. I lost a very expensive EDF jet when the 6S 5000mah fan battery decided to melt down in flight. Not only did I lose thrust (deadstick). but I also lost radio control which resulted in a crash. So, on every airplane i have (with the exception of some small foamy airplanes) I run a separate receiver battery and disable the BEC if the ESC has one built in.


        • #6
          Using a separate "flight battery" pack to power the receiver and servos is not practical for small electric powered models. A built-in or separate "switch-mode" BEC device as described on Dimension's website is NOT "hype" , thousands are in use successfully. Speed controls intended for use in models using 4 or more cell battery packs and/or more than five servos must have a built in or add-on "switch mode" BEC of adequate current capacity or use a separate battery pack to power receiver and servos without fear of "brownout" of power to the receiver resulting in loss of control. Cheap speed controls often have "linear-type" BEC circuits that can over-heat and cause brownout crashes when using more than 3-cell lipo packs and more than three servos.The motor current rating of speed controls is not indicative of the type and capacity of the BEC although most popular brand "40 amp" and higher-amp speed controls come with adequate switch- mode BEC's.

          I am an RC modeler who learned his lessons about BEC's many years and a few "brownout" crashes ago. Don't buy or use a speed control unless you are sure that it has a switch-mode BEC that is rated for the number of battery cells ( voltage) and number of servos that you are using(or) use a separate battery pack for receiver and servos. I don't use cheap speed controls and receivers in my built-up balsa/ply or foamy ARF models ,why risk a $100 plus model on a $15 receiver or speed control? Some foamy ARF models come with cheap no-name, unlabeled speed controls and no written instructions stating type of BEC and capacity. If I can't verify type of BEC in an ARF model, I will use one I can trust.