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Want to build a home-made generator

  1. Mar 20, 2008 #1
    First off thanks for the quick replys on my first post. Now, I'm looking to build a home-made generator, i've been told that I can just reverse the motion of a electric motor and *poof* it becomes a generator, is this true? And I was also considering just using a automobile alternator as my generator, But at what RPM would the alternator have to spin to give off efficient charge to charge a 12v car battery?
  2. jcsd
  3. Dec 6, 2008 #2
    that is dependent on the strength of the magnets and how much flux is created by the alternator.
    Unless you already have the details of the alternator, the best way is to just hook up an ammeter and volt meter and spin it yourself and take a few readings
  4. Dec 6, 2008 #3


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    From a backyard mechanic/racer perspective, I would assume that spinning your alternator at the basic idle speed of an engine (450+rpm) should provide an adequate charging output. That should be between 13 and 14.5 volts.
  5. Dec 6, 2008 #4


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    Staff: Mentor

    .... taking into account whatever gear ratio (if any) is applied by the belts and pulleys.
  6. Dec 6, 2008 #5


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    Gold Member

    Also you need to provide voltage to the field windings before you can get an output. For most auto alternators.
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