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more of a electromechanical question

Discussion in 'Electronic Basics' started by Neil, Jul 30, 2004.

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  1. Neil

    Neil Guest

    I am trying to get a small gas powered engine running, (Rockwell) and I need
    some help electrically. I have the unit running on the bench, with a simple
    on/off switch, and a 12 volt marine battery.
    I can get it started absolutely ok, but what I'm wondering, is it possible
    to have the starter motor charging the battery while its running, so it can
    power lights, just like a car does?.
    If I can do it, is it simply a matter of using a relay, that will take the
    electrical power generated from the the starter, once the engine is running.
    In other words a relay that will switch between running (starting the
    motor), and generating (running from the motor).
    Do I need to place a voltage regulator between the starter and the battery?.
    What do I need to keep the battery from overcharging?
  2. KevinR

    KevinR Guest

    Older small marine engines are often fitted with a thing called a dyno
    start, which is a starter motor dynamo and regulator all in one. The
    system is not terribly well liked and a lot of people remove the dyno
    starter and fit separate alternator and starter motor.

    The trouble with automotive starter motors is that usualy they are
    very crude and inefficient, because of the abundance of power
    available in a typical application where a starter motor is used,
    there is no point developing a more efficient/expensive solution.

    If your stater motor is not typical of automotive gear, and is of a
    reasonable quality, then it may be practical but you ned to regulate
    the output such that it will be suitable for your battery charging.

    You might look at fitting a separate alternator, you get a known
    working solution with regulator built in and they are very cheap from
    the local breakers yard.

  3. AC/DCdude17

    AC/DCdude17 Guest

    X-No-Archive: Yes

    The hybrid alternator/starter assembly used on marine engines isn't
    regulated well at all. The voltage can go up as much as 16V and this is
    bad for the battery.

    Use a small automotive alternator. They have a regulator installed
    already and it will maintain steady 13.8V to 14V even with varying RPM.
    You can tweak the pulley size to change the maximum output.
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