Dreaded White Wire - 6V 30W Spotlamp?

Discussion in 'Electrical' started by DuctTapedGoat, Apr 30, 2011.

  1. DuctTapedGoat

    DuctTapedGoat Active Member

    I want to hook up this 6V 30W spotlight lamp up to the generator without risking burning it out with too much voltage. It's rated 7.5V .5A on the Raw 2 stroker. I'm taking the multimeter to it later this afternoon to get my motors specific output. Should I use 6V worth of resistors to prevent it from shorting out the bulb, is there another electrical component I should use instead, or will the light only take 6V and no more than that?

  2. GearNut

    GearNut Active Member

    The light will not be hurt by 7.5 volts. What does concern me though is the white wire is typically rated at 6 volts, 3 watts, .5 amps.
    How are you going to power a 30 watt bulb with an alternator that only puts out 3 watts?
    It will most likely overwhelm the alternator and kill the signal going to the CDI from the mag side of the engine's coil. No spark= no run........
  3. DuctTapedGoat

    DuctTapedGoat Active Member

    I don't know - yet. I really want this lamp to work cause it's going to be very safe for me - to see and be seen.

    I'm going to have to go with a battery pack, but I don't know how to crunch electricity numbers (obviously, eh?). I'd like to know how to figure out what numbers I'd need to know to be able to A; Figure out how long it would take to charge, B; Figure how much time I have with the lamp on a full charge, and C; Figure out how to charge the pack with the generator off the bike.

    Heck - I'll daisy chain roller generators on my rim if I have to.
  4. GearNut

    GearNut Active Member

  5. pbeggs

    pbeggs Member

    electrical calculations

    to figure watts volts times amps 6 volts times .5 amps = 3watts
    to figure amps watts/volts 30watts/6volts = 5 amps
    to figure runtimes/chargetimes
    every battery has an amp-hour rating if you have a 10 amp hour battery and you draw 5 amps it will run the light for two hours amp-hr/amps=hours run time

    for charging if you are trying to charge a 10 amp hour battery with a 1 amp charge it will take 10 hours (20 hours with the white wires .5 amps)

    the electricity off the white wire is ac it cannot be used to charge a battery directly (which would be dc) there is a module availible on ebay which will convert the white wire electricity to dc,.. but you may not want to draw power from there as it can cause problems starting the same ebay vendor sells a coil that mounts on the magneto and provides lighting power it is expensive but works although would not be powerfull enough to run the bulb you want to run directly (you would have to ride for 10 hours with the light off to charge the battery to ride one hour with the light on)
    this ebay store has some of the stuff you may be interested in (it is expensive) good luck! i have used some of the stuff from these guys it does work but im just running 6v 3 watt bulbs
  6. loquin

    loquin Active Member


    There's an old thread here in this forum, discussing the fact that only HALF the AC cycle is used for ignition; you can get quite a bit more than 3 watts from the half of the cycle that isn't used by the engine. I VERY much doubt that it would support ten times that, though, (especially for very long!)
    Last edited: May 3, 2011
  7. loquin

    loquin Active Member

    I think you need to get about 30 or 40 of those 'shaker' flashlights! Space them around your wheel and be sure to use LOTS of Duct Tape!!! As you drive, the magnets slide up and down, generating power!

    The flashlights power are all wired together, and get to the stationary part of the bike through a slip-ring arrangement, to feed your headlights!!!

    Talk about a Rube Goldberg apporoach!
  8. DuctTapedGoat

    DuctTapedGoat Active Member

    I finally pulled out the multimeter - white wire gave me 4 volts at idle, and almost 10 volts at 3/4 throttle.

    I'm going to look into roller generators, and see what I can do about rewrapping them. One off the front, one off the back and the add in magneto to 12v.

    That should give me a decent output!

    And Loquin, you're silly. :p It'd be cool if that would work, but the centrifugal force would keep them pushed to the outside. :(
    Last edited: May 3, 2011
  9. GearNut

    GearNut Active Member

    You should be able to get nearly 12 volts out of the white wire when the engine is at screaming high RPM's. Do not be fooled by this though. Testing the alternator with a typical meter this way will let you test the unloaded output of the alternator.
    There is really nothing for the available voltage to power up so it goes way up.
    No load to work against.
    As soon as a load is applied, the voltage will go down as it now has to do some work.
    Try your test again, only this time hook up a 6 volt light bulb to the white wire first.
    You will notice a big change in the meter's reading.
  10. DuctTapedGoat

    DuctTapedGoat Active Member

    I don't know much - but that I did know. I'd like to find a way to reasonably do an alternator w/battery situation @ 12volts - and be able to relatively sustain it. Not 24/7 lamps, but be able to get a 2 hour output for 3-4 hours riding.

    I love and hate pursuing these kind of things - I learn a lot, but I also learn a lot about why it wouldn't be able to feasibly work.