Bicycle 12v dc charger advice help

Discussion in 'The Projects Forum' started by Neoleaver, Jun 28, 2012.

  1. Neoleaver

    Thread Starter New Member

    Jun 28, 2012
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    Hey folks, I have been gifted an electric bike that turned out to be too costly to restore. I initially planned to use the frame structure and 24v dc motor (rated 250W 10A @2650rpm) as the basis for a VA wind turbine. After wails of dismay from my children, who have adopted the bike as a novelty toy (it has tiny wheels and a hysterically bouncy seat), I decided that it might be a fun project to transform it into a charging generator for the remaining 12v 12Ahr battery that came with the bike (the other is shot). It was fairly simple to strip down the unnecessary lighting/ horn etc and reverse and lock the drive freewheel mech to spin the motor under pedal power. It happily produces 10-20v (no load) at reasonable speeds and I doubt the current is exceeding 10A (tho I'm unsure how to measure with my multimeter, electrics have just never been my 'thing'). I have been offered a 12V 10A solar charge regulator for free, does this sound suitable? Any advice on how to wire this thing would be most welcome! The 'concept' is to then take the successfully charged battery and use in a portable power pack that would incorporate an inverter to power low wattage appliances around the house. I'm not expecting big savings on my electricity bills, just a fun way to teach the kids (and myself) about alternative power. Any help would be most gratefully received.
     
    Last edited: Jun 28, 2012
  2. Neoleaver

    Thread Starter New Member

    Jun 28, 2012
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    0
    Just a little additional info on the battery the ratings are: Cycle Use (???) 14.4-15V, Standby Use 13.5-13.8V, Electric Current 1-1.5V.

    additional question: would the solar charge regulator I have been offered ( input overload control rating 17V) still charge the battery if I'm generating less than the battery rated voltage or will I have to exceed this.
     
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Sounds like a fun project. if you could post a model number (or even better, a link to manual or datasheet) of the regulator we could get a better idea if it will work. I'm optimistic though.
    You would probably have to pedal fast enough to keep the voltage >13.8V for it to work; I doubt the regulator has any step-up circuit, but could be wrong.
    here's some info about how much power humans can produce on a bicycle generator.
     
  4. Neoleaver

    Thread Starter New Member

    Jun 28, 2012
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    Thanks for the interest Strantor, I'm collecting the regulator this weekend so I'll post the details on here. any advice on how to take a current reading? do I just connect the motor's terminals direct to the multimeter as if I was taking a voltage reading? I'm just a little wary of damaging the motor and/or meter. I did briefly try this way, it had the same effect as shorting the terminals whilst spinning the motor in that the the motor became very hard to turn. My mechanically oriented brain is alarmed by this as any resistance to rotary motion usually indicates that all is not well!!! I do realize the motor will be appreciably harder to turn under the load of charging a battery. My rather vague understanding is that when measuring voltage there is a lot of electrical resistance and when measuring current there is very little.......so the motor then is 'pushing' much more current through the circuit? Please forgive my ignorance, electricity and all the peculiarities thereof, is probably my weakest area of knowledge.
     
  5. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    All is well. With your meter in current mode, the meter is a short. Your results are to be expected. I wouldnt try it again though as you might blow the meter fuse. Turning the rotor with the motor shorted out can generate vary high currents. To test the current while charging the battery, you must break the circuit and insert the meter. So go from the pos post of the motor to the pos lead of the meter, neg lead of the meter to pos post of the battery, neg post of the battery to neg post of the motor.
     
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