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Limit car battery current

Discussion in 'Power Electronics' started by pidja105, Jan 28, 2016.

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  1. pidja105

    pidja105

    106
    1
    Oct 16, 2015
    Hello,
    I have a question,
    can I use R = V / I formula
    to calculate resistor for 41 amps and 12 volts?
     
  2. shrtrnd

    shrtrnd

    3,717
    469
    Jan 15, 2010
    Yes, but what the heck is running at 41 amps in your 12V car?
    Are we talking about starter amperage when you crank the engine, or is this another issue?
     
  3. pidja105

    pidja105

    106
    1
    Oct 16, 2015
    No,
    it is for my electronics projects.
     
  4. Alec_t

    Alec_t

    2,788
    742
    Jul 7, 2015
    So which project requires 41A?
     
  5. BobK

    BobK

    7,680
    1,685
    Jan 5, 2010
    Ohms law will tell you what resistor would draw 41A if placed across a 12V source that is capable of that current. This is not very useful. Tell us what you are trying to do.

    Bob
     
  6. shrtrnd

    shrtrnd

    3,717
    469
    Jan 15, 2010
    BobK is right. Trying to draw 41A for an extended period of time from a 12V car battery is not going to last very long.
    More information will help us help you.
     
  7. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Please note that this problem can be looked at one of two ways:

    If your device is meant to pull 40 Amps, then it will only pull 40 Amps. You don't need to limit this, just hook it up if the device is rated for 12V.
    Otherwise, if you are building a switch mode power supply, current/voltage limiting should be done on that circuit.
    Finally. If you are concerned with 'Anything' taking more than 40Amps. Use a fuse. It won't dynamically turn down the voltage to stop you from pulling more than 40A, but it will still stop you from pulling more than 40A for any more than a second xD
     
    Tha fios agaibh likes this.
  8. hevans1944

    hevans1944 Hop - AC8NS

    4,460
    2,075
    Jun 21, 2012
    Sure. I'll even plug and chug the numbers for you: R = 12/41 = 0.29268292682926829268292682926829 Ω
    How's that for service?

    Your turn: what are you trying to do? What electronics projects? Please answer
    @BobK's question (post #5).
     
    Gryd3 likes this.
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