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DC Motors

  1. Apr 30, 2009 #1
    Hi, this is my first post so sorry it is not a contribution!

    Anyway, I have a pedal powered business that is doing very well. We use 24v DC Motors as seen here
    http://buggies.builtforfun.co.uk/FactFiles/motors.html" [Broken]. Each motor is connected to the back wheel of the bike (we use a diode next to each motor), so when people pedal it creates about 100w. My question is about wiring. To save time, 3 or 4 of the bike generators are wired in parallel so that we only have one wire per four bikes returning to the charge controller where they all join up. Each bike was tested prior to the event, producing about 5 amps each (we operate a 24v system). However, we found that when all 12 bikes were operated together we only seemed to manage a maximum of 18amps. This was bizarre. I expected to get at least 800w, not 250w.

    I hope this is somewhat clear.

    So my question is, because we have these generator in parallel motors are somehow cancelling out each other? Is there a better configuration other than wiring each motor back to the charge controller individually?

    Thanks for your help!
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Apr 30, 2009 #2
    What is the load on these generators?
  4. Apr 30, 2009 #3
  5. Apr 30, 2009 #4
    Thanks. How are the generators isolated from one another?
  6. Apr 30, 2009 #5

    there is a diode on the + side of each generator to prevent the current of one motor driving the other. The three groups of four motors join together. Here is a rough diagram that I hope you can make sense of (attached)


    Attached Files:

  7. Apr 30, 2009 #6
    I think I understand. You are paralleling voltages. That makes it a little easier on everybody and may get the caps charged faster due to a reduction in series resistance (I can't tell all that from the diagram, but that looks right). However, the currents in parallel don't add.
  8. Apr 30, 2009 #7
    It seems to me that if one motor is generating more voltage than another, the diode of the motor with less voltage will be reverse biased and none of the energy from that motor will be used.

    To do what I think you want to do, all of the diodes must be forward biased. That means the voltage of the capacitor must stay below the voltage of the motor generating the least voltage.

    Maybe you just need a bigger capacitor or perhaps a rechargeable battery.
  9. Apr 30, 2009 #8
    Belay my post. Skeptic2 sounds right.
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