alternator temp increase

Discussion in 'General Science' started by NAVYCHIEF, Dec 21, 2009.

  1. NAVYCHIEF

    Thread Starter New Member

    Dec 21, 2009
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    what happens to the output of an automotive alternator as its temp increases?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Chief,
    That's an interesting question, and I don't really have a good answer for you.

    One of the reasons is that there are a huge number of different manufacturers and models of alternators.

    Another is that the operating environment is quite dynamic; the output of the alternator more or less depends upon the load placed on it.

    It would help a great deal to narrow such a broad question down, to just a specific make and model of alternator, and then test it under known load conditions at a constant rotational speed, varying only the temperature, in order to observe the results.

    Your results will likely vary between different manufacturers and models.

    But usually, a typical alternator will output around 13.8v to 14.4v when the engine is above idle speed.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    To try to answer your question better....

    The engineers who designed the voltage regulation system try to ensure that the voltage output will be consistent over a wide range of operating conditions, and be reliable, yet capable of being mass-produced at a low per-unit cost.
     
  4. thyristor

    Active Member

    Dec 27, 2009
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    The alternator voltage regulator is designed to reduce its voltage output as its temperature increases and vice versa for temperature drop.

    This is because, as a lead acid battery gets hotter, it requires a lower charge voltage, as compared to the required charge voltage at room temperature, to avoid overcharging it.

    Because an automotive alternator is usually in close proximity to the battery (viz: under the hood) the regulator designer assumes that the alternator and battery will experience similar ambient temperature changes.

    This can cause charging issues in a non-automotive environment (eg: a boat) where the alternator and batteries may experience widely differing ambient temperatures and thus the charging curve may be compromised. This can be overcome on a boat by utilising an alternator controller (external regulator) which senses inter alia battery temperature.
     
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