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VF250XA Isolater lead

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  • #16
    Does anyone have any idea about how many RPMs an alternator is turning when a Auto engine is at a normal cruse speed of say 60 MPH?
    My PU truck motor is only turning 1500 RPMs and I am sure it is charging max at that point (maybe).

    Air cooling an alternator under the hood of a outboard motor probably would not work well enough.
    May have to water cool and set it up on top on motor instead of off to the side.

    I can see where problems could come from

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    • #17
      Originally posted by 99yam40 View Post
      Does anyone have any idea about how many RPMs an alternator is turning when a Auto engine is at a normal cruse speed of say 60 MPH?
      My PU truck motor is only turning 1500 RPMs and I am sure it is charging max at that point (maybe).

      Air cooling an alternator under the hood of a outboard motor probably would not work well enough.
      May have to water cool and set it up on top on motor instead of off to the side.

      I can see where problems could come from
      The designed speed for the application can be determined. If you measure the diameter of your engine pulley and then measure your alternator pulley and divide that into your engine pulley dia times 1500 will give you its revs. If you monitor the alternator's voltage and gradually slow down from 1500 until the voltage clearly drops you can determine the minimum speed ( minimum revs with your ratio obtained) at which the alternator needs to turn to be in it's useful output rev range.

      You of course already know this, it does not answer your general question: at which revs does an average alternator need to spin?. By doing the calculations with a number of vehicles I suspect some mean can be derived (I have not done this). Alternator data is probably hard to obtain. In practice data obtained will tell you more.

      I meant also to say earlier, there is absolutely no need to "bleed off" excess energy available in flywheel magnet generators! It is because they are not built with adequate voltage regulators. The practise continued because one end of the coil is earthed where there is no need for this; and also all the output needs then to go through this regulator impacting on cost. The alternator regulator needs far less to go through it because it only supplies the rotor.

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