Trying to power headlights on Snowmobile

Discussion in 'The Projects Forum' started by GoodysGood, Aug 24, 2011.

  1. GoodysGood

    Thread Starter New Member

    Aug 24, 2011
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    Hey guys I'm new here and this is my first thread/post.

    I am going to get right down to the details. I have a snowmobile that needs to power 12v lights. The problem is that it produces approx 11.4v idle. I want to hook up a battery to them to power the lights when the sled cannot produce it by itself. When the sled gets above idle and can produce the 12v needed I need to have some sort of switch that stops using the current from the battery and gets the power from the sled. I've been looking for a few hours and cannot find exactly what I need.

    Please be gentle with me lol.
     
  2. wayneh

    Expert

    Sep 9, 2010
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    So when your sled is idling, the onboard battery (you do have one?) cannot maintain voltage to keep the lights bright? That's pretty normal but might indicate an aging battery.
     
  3. MrChips

    Moderator

    Oct 2, 2009
    12,441
    3,361
    A simple diode should do the trick but then you would not be able to charge the battery from the snowmobile alternator.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,123
    3,047
    The voltage drop across the diode might only get him back to where he was. But it would "disconnect" the battery once the alternator voltage comes up.
     
  5. GoodysGood

    Thread Starter New Member

    Aug 24, 2011
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    Charging the battery shouldn't be a problem because I will have it set up on a charger in my shop when it's not in use.

    No it does not have an onboard battery. The lights will not turn on unless there is a minimum of 12 volts running through them to power them up. They are HID lights by the way guys so you know what I'm working with.
     
  6. vini_i

    New Member

    Apr 19, 2010
    14
    1
    correct me if i'm wrong on any of my points.
    the snow mobile is of the pull start variety.
    the ignition and charging system are like a lawn mower or snow thrower.
    the spark plug is fired by a magneto type ignition and does not depend on the alternator.
    the alternator is only used to run regular head lights that come on when engine is running.

    generally a lawn and garden alternator is compatible with a battery. it will either be a one wire variety (the other side is grounded to the block) and use half wave rectification via a built in diode or a two wire alternator that uses a voltage regulator that is attached to the side of the block and has a one wire output.

    if all the points i made are correct here is what i would do. hook the negative side of the battery to the block directly. hook the positive side of the battery to the charge wire with a switch in the middle. hook the charge wire to your lights.

    when the rpm is low the battery will power the head lights. when the rpm is high the alternator powers the head lights. you should be able to keep the battery hooked up the whole time because the alternator is generally designed to charge lawn and garden batteries anyway and the switch will allow you to turn the head lights off when the motor is not running.
     
  7. GoodysGood

    Thread Starter New Member

    Aug 24, 2011
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    Yes you are correct on all of those points. I cannot say for sure if the ignition system is magneto or not but from all of my options this seems the most practical.

    The sled is a 2002 mxzx 800 and apparently this is the first year they introduced AC into them. Would i have to buy/make a rectifier because they don't have one on the alternator. (from what I hear)
     
  8. vini_i

    New Member

    Apr 19, 2010
    14
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    is it a one wire alternator or two wires?
     
  9. GoodysGood

    Thread Starter New Member

    Aug 24, 2011
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    It has 2 wires and a ground
     
  10. vini_i

    New Member

    Apr 19, 2010
    14
    1
    is this a belt driven alternator or is it under the flywheel with the three wires sticking out?
     
  11. GoodysGood

    Thread Starter New Member

    Aug 24, 2011
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    Its off of the flywheel but looks like its a stater not an alternator vini
     
  12. vini_i

    New Member

    Apr 19, 2010
    14
    1
    i did some reading and correct me if i'm wrong but one alternator wire is green and the other two are yellow.

    from everything i found your alternator is of the delta variety. these kind of alternators always have regulators. with a volt meter check what kind of voltage is at you head lights. check both on the DC scale and the AC scale. normally if an alternator is regulated you'll see like 10v dc at idle and less then a half a volt AC.
     
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