Questions/ Solution for charging system?

Discussion in 'Electrical' started by AnvilBlockForge, Apr 15, 2013.

  1. My original plan was to charge a 12v 4.5A battery from the engine. I connected a meter to the same device that provides spark to the engine and it supplied 1-18V of power. So my plan was to use a 12v Rectifier/Regulator to charge the battery which in turn would power the lights.
    Now I just recently been told that if I wire the battery to that it will act like a kill switch and kill the engine. Is this true, and if so, what are my other options to charging a battery?
    I'm in the wiring stage of my build, so I'm kinda stumped :thinking:
    I'm not all too familiar with the electronics with these motors, so maybe the picture will help

    Attached Files:

  2. jaguar

    jaguar Well-Known Member

    yeah you cant use the same coil to both power lights and run the ignition system.

    you might consider one of these small electric generators that is friction driven at the wheel.
  3. KCvale

    KCvale Motorized Bicycle Vendor

    I have no clue what that motor even is but when it comes to good lighting I learned early that using any motor power to generate light just isn't worth it when there are so many other better lighting systems like a nice CREE LED and small Lithium Ion rechargeable 8.4V 4-cell 18650 battery pack.

    This one is pretty cool for under $30 delivered...

    But there are others.

    I don't do much night riding but if you do just get a second battery pack and charge them up with the included charger when needed.

    I get the most use of it riding in bright sunlight in strobe mode and it lasts for weeks before a recharge.
    Here is a Utube video of my newest electric trike with that light on the front.

    All can tell ya is I know first hand how a daylight stroke has saved my skin and you can see from that video why, it just flats gets your attention before you even see what it is making the light ;-}
  4. Would it be possible to use the motor to charge the battery and the battery to power the spark plug?
  5. It's a Tecumseh H35 153cc 4 Stroke from a tiller
  6. jaguar

    jaguar Well-Known Member

    If the coil charges a battery for use by the ignition system there has to be a trigger pulse from a separate detector on the magneto telling the system when to fire each revolution.
    Yours is a system like the Grubee uses in that both timing and voltage is derived from the same coil.
  7. KCvale

    KCvale Motorized Bicycle Vendor

    Well said, the ignition coil is timed to fire just before Top Dead Center.
    The 2-stroke coils have a second winding you can tap for Aux power but what you find is when you turn on the light the idle drops so far it kills the motor and why some people hook the kill switch across it.
    Sure you can idle up to compensate but then when the light is off it revs too high.

    If you are hell bent on making the motor charge a 12V battery put a generator in the drive line, it will only charge when you are moving and not effect the motor directly.
    There are example of little gen with a chain sprocket mounted between the motor and rear wheel but I'm not sure where.
  8. professor

    professor Active Member

    Anvil, here is what I did- (I need lights on at all times in this state.)
    Take a 24v scooter motor and drive it off the output shaft of the engine at 1/2 engine speed.
    My bike # 1, has a little 150 watt motor off a razor scooter (adapted to belt drive) and my bike 2 has a 250 watt (#25 chain drive) on it.
    At full revs the voltage is way over 12, and at idle, the lights are not very bright. Am using regular old style bulbs ( like in a tail light).
    No voltage regulator needed.
    I am using HF engines that only rev to between 4 and 5 grand.

    Much more rpm and the ratio of drive to the "Generator" would need to be lowered to keep the bulbs intact.
    The old mopeds used the same idea only the generation is internal in the engine case.
    A good source of new motors is All Electronics corp in Cal. Or an old electric scooter.
  9. Funny you mention that, that was actually my plan if this one wouldn't work. There's a groove for a belt around the flywheel. So I was thinking of making a bracket and running a belt from a 24V 100W Scooter motor to the flywheel. Run the motor top a regulator/rectifier to charge the battery. Would that work?
  10. professor

    professor Active Member

    It would work for a short time- you would over rev the "generator" unless you go with a huge pulley on it.
    These motors only go a couple of thousand rpm (advertised).
    Big drag on the engine too without a huge pulley.

    Like I said, I run mine at half engine speed, so if the engine is at 5000 (wound out occasionally)- the "Generator" is at 2500 - which would be OK.
    I am going by memory on the scooter motor rpm.

    Depending on how much light you need ( I just need a bright glow- almost never ride at night) you can step up to 250 w or more. Or possibly an LED.
  11. I'm running headlights, brake lights and turn signals (as required by law) and I have a High beam I added. So I need a battery to be able to always have them bright. But I have no idea how I'm gonna charge it. I've just read mixed reviews on the generators that run from the tire, that they break after a while. And if you say the scooter motor won't work, I'm back to square one