DC motor generator/charger

Discussion in 'Electric Bicycle Batteries and Accessories' started by machinegun4784, Sep 13, 2016.

  1. machinegun4784

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    Could someone please explain how to turn a little RC toy motor into a battery charger?
     
  2. mogollonmonster

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    Hook positive and negative motor leads to their respective battery terminals. Spin motor shaft very fast to generate electricity. Do not use "tiny RC motor" use a 540(550) size motor or larger, the other important number, denotes the number of turns. The lower the number, the more juice it'll put out when spun at a certain speed. Thus a 27 turn puts out more juice than a 50 turn, despite both being 540 size motors.
    You will need to mount some kind of friction roller to the shaft, then secure the motor to your bike, with the roller against a wheel. Horizon hobby makes decent electric motors under $20, but an actual bicycle dynamo generator will run you about $12, for the genny, a light and mounting gear.

    Good luck, a 550 size RC motor could put out lots of juice, and last a really long time too.
     
  3. machinegun4784

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    That's the shlt I'm lookin for! Thanks man, yer the best.
     
  4. mogollonmonster

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    There should also be fuses in there and a charge controller of some kind and whatnot. What I described above is kinda primitive, but as long as you don't overcharge the battery, you'll be fine. More primitive yet, wire the DC motor straight to the light, that's how most bicycle dynamos work. Their "switch" simply moves the roller wheel away from your tire. I found one from randombikeparts.com that's the only branded unit I found, it's a Sanyo. The light is crap, but the genny block is good quality. I'd post a direct link, but you'll be fine googling bicycle dynamo. Lots of options. If my RC gear hadn't been stolen, I'd have just built my genny from spare parts. I had a 3 turn Cobalt motor that would have made some serious juice.
     
  5. machinegun4784

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    How do I keep it from overcharging?
     
  6. mogollonmonster

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    I have no idea honestly, some kind of charge controller or relay, or resistor or some such.
     
  7. WECSOG

    WECSOG Member

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    Use the power it produces. Basically, design the entire system so that you break even or a little less. If you design a system that overcharges the battery, you're wasting energy.

    Sounds simplistic, but it's the way the most ubiquitous motorized vehicle ever made (the Honda Cub) was designed. If everything was up to snuff, it worked great. But if the headlight burned out and you didn't replace it soon, it would boil the battery dry.
     
  8. curtisfox

    curtisfox Active Member

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    #8 curtisfox, Sep 15, 2016
    Last edited: Sep 15, 2016
  9. mogollonmonster

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    Thanks guys, bout time someone else with more savvy came along.
     
  10. sbest

    sbest Member

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    Use a shunt regulator like on a snowmobile or trailbke.
     
  11. machinegun4784

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    Wouldn't a Zener keep it from overcharging?
     
  12. sbest

    sbest Member

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    It would if you only wanted 3.6 or 5.2 volts and could keep the Zener diode from burning up from the current. When you pack it together with voltage divider resistors to get the right voltage and a current carrying transistor and a heat sink and all that, it is called a "voltage regulator" and it shunts excess voltage off as current to ground. Costs as little a $5 bucks brand new for a cheap Ebay sample or $50 for a KTM product that does the same thing.

    There are integrated circuit specific voltage regulator chips as well, but require a current carrying transistor and enough knowledge of electronics to put it together that you wouldn't ask this question if you knew how to build it. Better to use a shunt regulator.

    Old snowmobiles or trailbikes will give you a workable sample. They don't fail very often.

    Steve
     
  13. machinegun4784

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    OK so I got this dynamo in the mail today. Its a 12v 6w 4 pole. Looks like it's putting out AC. I have 3 Li-Ion 12v batteries I'm using this thing to charge on the road. Can I hook up a rectifier/regulator? Or perhaps someone could just tell me what to do to make this work?
     
  14. machinegun4784

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    So is it a trade secret or is everyone just stumped?
     
  15. sbest

    sbest Member

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    Got a picture or wiring diagram?
    Yes, hook up a full wave rectifier. How many wires out do you have?
    Now you will have DC volts increasing with engine rpm.
    Connect the shunt regulator across + and - and it will regulate to 13.8v-14.3v.

    Usually we run the headlight and other high loads like grip warmers off the AC because there are losses through the rectifier. In that case we use an AC shunt regulator (off a system with no battery) on the AC and take what we get off the rectified side. Many roads to Rome.

    Steve
     
  16. machinegun4784

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    This is the model I bought. I don't know what kind of guts it has.

    https://www.amazon.com/Generator-bi...F8&qid=1474341203&sr=8-4&keywords=dynamo+bike

    It just has the two electrodes you see on the bottom. Do I need two individual components? I thought reg/rect came in one block. Also I think 13v may be too much. It's right at 12 with the wall charger I use. I would really need a diagram or explanation of how to rig it up. I can sure use a voltmeter, but I do not get charging.
     
  17. Kletus

    Kletus Member

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    Go to ebay, search in (wind generator). You will find all kinds of 12V dc motor generators and alternators. You will also find voltage regulators (charge controllers). The generators with rare earth magnets or neodymium magnets are the highest efficiency and work better at low rpm's. You probably wont need much more than 100 or 200 watts. 100 watts @ 12 volts is about 8 amps, you might only need a 50 watt (4amp) depending on what your trying to power.. Toy motors have weak low quality magnets and don't generate much current. The generator/motor should be the type with permanent magnets. You could run it from the drive chain, of course it would only generate power when you are moving. Something that I bet nobody has tried is using an old front hub electric bike motor for a generator. rip all the electronics out, you should have 3 wires coming out of the motor its self, connect these wires to a 3 phase rectifier and you have dc power.
     
  18. Kletus

    Kletus Member

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    Go to ebay, search in (wind generator). You will find all kinds of 12V dc motor generators and alternators. You will also find voltage regulators (charge controllers). The generators with rare earth magnets or neodymium magnets are the highest efficiency and work better at low rpm's. You probably wont need much more than 100 or 200 watts. 100 watts @ 12 volts is about 8 amps, you might only need a 50 watt (4amp) depending on what your trying to power.. Toy motors have weak low quality magnets and don't generate much current. The generator/motor should be the type with permanent magnets. You could run it from the drive chain, of course it would only generate power when you are moving. Something that I bet nobody has tried is using an old front hub electric bike motor for a generator. rip all the electronics out, you should have 3 wires coming out of the motor its self, connect these wires to a 3 phase rectifier and you have dc power.
     

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