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  1. #1
    RC Enthusiast
    Join Date
    Dec 2012
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    22

    Do I NEED a BEC?

    This isn't necessarily limited to a revo but it is about the MMM in multiple vehicles, I hope this is permitted:

    I have a revo, TTR ST-1 truggy (converted to brushless) and Hyper 9e running MMM/2200kv in the trucks and MMM/2650kv in the hyper 9e. I have Hobbico CS-170's in all 3. I noticed in the MMM for the truggy and buggy I can change the BEC from 5-7v but in the revo it is grayed out and says 5.5v. I'm not doing anything fancy but would I see any benefit from running an external BEC on these vehicles or is the stock BEC on the MMM good enough. I have read that most newer MMMs actually output 6v fixed instead of the original 5.5v. Is there an easy way to measure this? It just seems like a lot of extra wires and maybe one more thing to fail or troubleshoot should an issue arise. But some people say they are always healthier for the ESC. Please advise. Thanks

  2. #2
    RC Champion
    Join Date
    Aug 2012
    Location
    Central NJ
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    1,245
    In response only to the Castle MMM installed in the ERBE as its against rules to discuss other than traxxas....

    All of Castles ESC linup seems to be weak on the internal BEC. The MMM that comes with the ERBE is most likely locked to prevent anyone from increasing the voltage too much and cooking the traxxas RX. You can measure the output voltage with a DVM across the brown and orange wires on the lead that plugs into your RX.

    The need for an external BEC is dependant on what servo you run for the most part. If you are running a power hungry savox its pretty much a guaranteed bet that you need an external BEC. If you are running high voltage servos designed to run on 7.4V you either need an external BEC or can run them directly off of a 2s tap (this is what I do). An External BEC really doesnt have an effect on the ESC overall, its a seperate circuit over what powers the motor.

    There is no need to raise the voltage if you arent having issues with the servo dragging down the voltage and causing glitches, brownouts or blackouts.

    Better advice can be given on the traxxas model if you list what you are running that is a load on the BEC. RX, servo etc.

  3. #3
    RC Enthusiast
    Join Date
    Dec 2012
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    22
    That's it, I replaced the 2 stock servos with the Hobbico CS-170 servo. Other than the stock rx there is nothing else plugged in. I'm not even having any issues so maybe I am just trying to create one (LOL)? I think really I am just wondering if the servo would perform even better (its great now) with a BEC.

  4. #4
    RC Champion
    Join Date
    Aug 2012
    Location
    Central NJ
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    1,245
    You wont see much of a difference between 5.5V and 6V on that servo. If you were running a 7.4V servo you would notice more torque and speed. My advice if you arent having problems is to leave it as is.

    I got pretty elaborate on mine and run right off of the balancing plug on a 2s pack and right into the RX and clipped the + going to the ESC (actually clipped the + on the short servo extenion I put on there because I didnt want to alter the ESC lead). Difference is though Im running a JR Z9100HVT that is a 7.4V servo and my RX is a Futaba R614FF that is rated for the higher voltage also.

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