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Electronic Speed Controls & Brushless Motors

  1. May 26, 2012 #1
    With an ESC powering a brushless motor, does the ESC get power feedback? Sorry I don't know the terminology, so I'll ask it a couple of ways.

    The power from the esc runs through a big length of wire windings. I get this isn't a short circuit since enough of the power is turn into heat, does the magnetic field it self also use power being generated, like the heat?

    If the motor is not turning, but equal power still applied from the esc, does more power get back to the esc just because the motor isn't turning? Would the motor/esc get hotter? (outside there being less air movement)

    Just want to understand these things a bit better.

    I have no idea is if this matters but power would be around 100amp / 8volts / 800 watts or less amps.
  2. jcsd
  3. Jun 9, 2013 #2
    Hello Everyone,

    As this thread is a NR, please allow me to ask a question also pertaining to ESC and brushless motor.

    I went to a RC shop asking the price of a high torque motor and the ESC , charger and betteries, the whole set, excluding the flying machine.

    I was shocked to hear that the ESC is many times more costly than any other components.

    I suspect the shop keeper was pulling my leg as I was asking many questions and he may be trying to deter me from asking more by quoting a very high price, sensing I was there to ask and learn instead of buying anything.

    So, being a greenhorn at RC, I like to get some advice from you, if you could spare me some comments.

    I asked for a 245KV (rpm / Volt) brushless outrunner and the recommended ESC , lipo batteries and charger.

    Here is the following price quoted to me :
    1. 245 KV motor : US$200
    2. ESC : US$500
    3. Lipo 6S 4200mAh : US$80
    4. charger (for charging 1 lipo stack at a time) : US$60

    I like to know is he trying to rip me off?
    The ESC is way higher than what i see on the net for smaller brushless motors.

    I am not using these for RC planes .
    Is it possible to use a simple ESC to control a large RC motor like this? i am just using it on a electric bicycle.
    i am not building a fast bike. Just a average bike running about 10km/h.

    Also, I estimate that at 70% constant speed, a fully charged lipo stack would run out of juice in 10 minutes.

    So, I would need many stacks of Lipo and a multi lipo charger to charge in parallel.

    Kindly could experts here share with me some of your knowledge?

    Thanks very much.

  4. Jun 10, 2013 #3
    Speed controllers are expensive - and they are the weakest link when abused, or not applied properly. My son bought a not too cheap electric exceed car - went through 4 ESCs and then gave up - felt bad for him at 12 yrs old he spent a lot of $ they were worthless for support.
  5. Jun 10, 2013 #4
    Which country Ramone? It does vary greatly both with production quality / R&D / warranty ect.
    China Direct very high spec ESCs can be had for well under $200.

    For example my "throw-away" china direct esc was good for about 2hrs of running, $40 down the tube. Bought N.American made/designed for $200, same specs (there about) and this thing has taken a ridicules amount of abuse, whats more is warranty support. If I smash it with a hammer or it otherwise breaks I mail it back +$90 for a brand new one. That's lifetime.

    If in some "normal trade" country that ESC is way to pricy based of of the power supply; 6s 4.2a/h batteries.

    That's only 22.2ish volts (25ish charged), and a 4.2a/h batt would be lucky to supply 150amp continuously. "Continuous" power type escs are actually pretty cheap, the cheapest. I shop "hobbyking" for "china direct" costs.
    Last edited: Jun 10, 2013
  6. Jun 11, 2013 #5
    Oh - as for bikes you can also look at Bionx, they also provide the "powertrain" for Trek bikes - they make thousands of e-bikes at ~ 300W, and they cost $$.
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