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Old 05-07-2010, 02:17 PM
diggerdave65 diggerdave65 is offline
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Join Date: Jul 2007
Location: burlington vt
Posts: 21
understanding electric on small eng

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!
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Old 05-07-2010, 02:51 PM
seabee24 seabee24 is offline
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Join Date: Mar 2009
Posts: 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
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Old 05-08-2010, 01:00 AM
rotti1968 rotti1968 is offline
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Join Date: Nov 2009
Location: branchville nj
Posts: 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.
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Old 05-08-2010, 01:09 AM
GravelyNut GravelyNut is offline
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Join Date: Nov 2007
Location: Wet part of FL
Posts: 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.
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Old 05-08-2010, 03:01 AM
topsites topsites is offline
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Join Date: Mar 2005
Location: Richmond Virginia
Posts: 21,659
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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