is it possible to pull any volts off the ignition

Discussion in 'General Questions' started by Ratty Natty, Sep 14, 2014.

  1. Ratty Natty

    Ratty Natty New Member

    Is it possible. or do we have to add a dynamo.

  2. crassius

    crassius Well-Known Member

    it isn't recommended
  3. KCvale

    KCvale Motorized Bicycle Vendor

    If you have a white wire from the engine you can pull power from it but not much and it will cause engine drag.
    For example with a normal idle the motor dies when you turn the light on.

    A dyno is a drag on performance as well but only when moving, in short there is no free power.

    If you are just looking for a good front light you could get away with a 4.7V LI LED bike light for ~$20 and charge the battery via the white wire with some circuitry to regulate the charge, that would be cool.
  4. Ratty Natty

    Ratty Natty New Member

    cool i was thinking there might be an aux there. Nothing comes for free. I was thinking of using it to trickle charge rechargeables as a last resort. I have an old school sanyo barrel type 6 volt dynamo. It sounds like the go. I will talk to my electronic engineer mate now I know something is there. I really want to run an old school light on my cruiser. Thanks
  5. HeadSmess

    HeadSmess Well-Known Member

    i went to the effort of stripping a magneto and rewinding it to pull 32 volts, unloaded.

    it drops seriously under load...(18 watts!) down to about 10 volts, max...current unknown. it sure wasnt lighting up to full brightness!

    the voltage is a function of turns of wire, rpm, magnetic strength, and load... theres only so many watts you can suck out.

    (basically...a short circuit is no volts, full circuit is no amps, full voltage. make sense?)

    i ordered a brushless motor of 80kv with the intention of setting it up to be both the chain tensioner and dynamo.

    why 80kv? because then it will produce (approximately) one volt at 80 rpm. the lower the kv rating, the slower it has to spin to produce a given voltage. a 3500kv would be useless in this application (chain tensioner would only spin at 530 rpm or so, max...making for about 30 volts...unloaded.).

    it hasnt arrived yet, and now the laws changing where i live so motorised bikes will be illegal in two weeks(october 1), so... i guess ill be using the brushless motor for some totally unrelated project when it does arrive.

    ive only ever had one stock magneto with the white wire that got an LED spotlight to work. those mr16 4w LED ones. 4w would have worked fine on my rewound magneto, i guess... but 18w was just a bit excessive!

    gunna be a good spottie on my new motorbike but :)

    oh. run the "old school light" but give it an LED bulb instead of the standard, dim lil incandescent... use a yellow one if the colour is a concern ;) (have two reverse wired as the dynamo will output AC, rather than DC)

    or green, to match the paint job...(you will paint it green, right?:jester: )
    Ratty Natty likes this.
  6. patthesoundguy

    patthesoundguy New Member

  7. HeadSmess

    HeadSmess Well-Known Member

    the coils pictured above will work...but dont expect 18 watts continuous output ;)

    fine for a standard 3 watt affair, better with some LEDs. a 1W led will put any 3w bulb to shame.
  8. darwin

    darwin Well-Known Member

    You really want some free juice check out some of those german made dynamos. Pricey but they work and will last a looong time. I just use rechargeable eveready batts. With LED lights 1 charge lasts like 24 hours using them and I never use them that long. Plus they're good for 100s of charges.
  9. Fabian

    Fabian Well-Known Member


    It's far more effective to simply purchase a good quality, high intensity bike light, that will be far more powerful than anything you can run off the magneto coil.

    SickBikeParts sells a very price competitive (and high intensity) bike light, which i can recommend, considering i have bought 4 of them, for myself and others.
  10. KCvale

    KCvale Motorized Bicycle Vendor

    Yep, $20 delivered.

    8.4V 6.6A (55W) CREE T6 3-mode 1200 Lumen LED (bright, dim, and strobe for daylight riding).

    Though plenty enough light the last couple I just ordered are 3600 Lumens but they aren't here yet.
    All I know is SBP's are over priced because every Chinese flashlight maker makes lights like this now and bargains abound.
  11. Whiteride

    Whiteride Guest

    You could awlays go with something like this little antique 1880's bicycle lamp, all you need is carbide,water, and a match... ;-) 05.jpg
  12. crassius

    crassius Well-Known Member

    I like those, but find carbide is getting difficult to get shipped here : (
  13. Whiteride

    Whiteride Guest

    Can't buy or import it into Canada, and guess what we export? Go figure. I like the look though and in our City it would be suicide to try and ride at night. If I did need a finctional bike light though, I'd opt for a simple battery powered LED retro one. Lots out there and very cheap. I also have a mount for my Surefire which would take care of any lighting needs as well.