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Another Newbie question about Power supplies

Discussion in 'General Electronics Discussion' started by SparkyCal, Apr 4, 2020.

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  1. SparkyCal

    SparkyCal

    362
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    Mar 11, 2020
  2. Bluejets

    Bluejets

    4,208
    893
    Oct 5, 2014
    I have a 4 cylinder car so how fast will it go.
    See the problem..??

    Assumption is your 9v battery is a common smoke alarm battery so current in mA.
    The internal structure of the battery limits the amount of current supply and the life span.
    A site Battery University has a great deal of reliable information on battery specs.
    https://batteryuniversity.com/learn/
     
  3. Nanren888

    Nanren888

    301
    68
    Nov 8, 2015
    Why?
    If you are simply trying to power something that normally uses a nine volt battery, then set the voltage to 9 volts.
    The current will just be what the circuit needs. Power supplies often offer a current limit that helps prevent accidents if connected incorrectly, or circuits are not as expected. You can set the supply up to limit the current to some sort of maximum that is expected from a nine volt battery. If as Bluejets asked, the battery is a standard 9V pack, then you can limit it to quite low.
    This page
    https://groups.google.com/forum/#!topic/sci.electronics.design/6nEUtCCNMYY
    suggests a peak current of about 600mA from such a battery.
    Depends whether normally takes standard dry cell or alkaline.
    .
    If you are trying to emulate a battery over its lifetime, as it goes from new to depleted, then much more complicated.
     
  4. Audioguru

    Audioguru

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    Sep 24, 2016
    Energizer makes 9V alkaline batteries and show a datasheet. It shows the voltage dropping with time when powering a 270 ohm load.
    You can simply calculate the current that is also dropping by using Ohm's law.
    If the resistance is lower then the current is higher and the time is shorter.
     

    Attached Files:

  5. Audioguru

    Audioguru

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    654
    Sep 24, 2016
    This is from Duracell's datasheet:
     

    Attached Files:

  6. SparkyCal

    SparkyCal

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    14
    Mar 11, 2020
    Thank-you. That helped but I asked my question in a twisted fashion. I will be re-asking it on a new thread, as it is a different question. My fault.
     
  7. bob.steel

    bob.steel

    16
    1
    Feb 27, 2020
    Set amperage at 500 mA and set voltage at 9 volts . Watch the little light . If it is being current limited the light next to that value will be lit . If it is being voltage limited then its light will shine for all to see.
     
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