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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


    Mar 11, 2020
  2. Bluejets


    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.
  3. Nanren888


    Nov 8, 2015
    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!topic/
    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


    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


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

    Attached Files:

  6. SparkyCal


    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


    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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