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understanding electric on small eng

Discussion in 'Mechanic and Repair' started by diggerdave65, May 7, 2010.

  1. diggerdave65

    diggerdave65 LawnSite Member
    Messages: 21

    Hi All -- can someone help me understand electrical generation in relation to a lawn tractor or ATV engine???(In this case the engine im talking about is a Techumseh OHV17). The tractor has headlights. So, when the engine is running and you have a battery on board and you turn the lights on - whose power are you using? Is it straight from the battery and the battery is getting charged by the running engine (I thought you would need an alternator to do that) OR are the lights powered by the engine (i thought you would need some sort of generation for that - Obviously the engine creates spark with the armature and flywheel, but can or is that fed out to the rest of the system??). As an aside I have an older Kawi Bayou 4 wheeler that has both electric and pull start. If I dont have a battery, and pull start it, the lights will work but are extreemly dim.. This leads me to believe that the power comes from a combination of both the battery and running engine.
    Appreciate anything that will help me understand!
  2. seabee24

    seabee24 LawnSite Senior Member
    Messages: 619

    could be wired either way , but generally speaking excluding the spark plugs the items that require power like your head lights, are wired to the battery and the battery is powered by the generator system. the gen system is normally mounted under neither the fly wheel in the form of coils
  3. rotti1968

    rotti1968 LawnSite Member
    Messages: 169

    Your normally have a ac charging system under the flywheel thats either coils or a stator. This ac power is regulated to dc power that charges the battery and maintains that charge. When you turn the lights on you are using the power from the battery and the charging system keeps the battery charged, when there is no battery in place the lights may not draw enough amperage for the charging system to even notice they are on and only supply enough power to lite them.
  4. GravelyNut

    GravelyNut LawnSite Bronze Member
    Messages: 1,594

    Some older engines had two coils to generate AC power. One set fed the lights while the other was half wave rectified for charging the battery, Some engines still only use half wave for battery charging but run the lights off of the battery.
  5. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Technically your battery is like a voltage regulator as both the lights and
    the engine's charging system are hooked into it, the lights would run with
    the engine off although the key may have to be On ignition.

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