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Problem about source

Discussion in 'General Electronics Discussion' started by vick5821, Aug 30, 2012.

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  1. vick5821

    vick5821

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    Jan 22, 2012
    hey, one very weird things. When my switch is off, my battery is 8V.But once I conneect it to the circuit and the switch is on, the voltage from the battery dropped to around 5V soemthing. Why ? Anything wrong there in my circuit ?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,306
    2,588
    Nov 17, 2011
    The current your circuit draws from the battery is more than the battery can deliver at full voltage. Think of the batery as an ideal voltage source with a series resistor (inner resistance caused by the battery's chemistry, its state of charge etc.). The current will create a voltage drop at this internal resistor. You cannot see or measure directly the internal voltage drop, but you see the voltage at the battery's terminals go gown as a consequence.
     
  3. vick5821

    vick5821

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    Jan 22, 2012
    Why causes this ? Any solving methods?
     
  4. gorgon

    gorgon

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    Jun 6, 2011
    What sort of battery is this, 9V?

    TOK ;)
     
  5. vick5821

    vick5821

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    Jan 22, 2012
    the rectangular battery :)
     
  6. gorgon

    gorgon

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    Jun 6, 2011
    Yes, but is it a 9V battery?
    If it is, it will be exhausted with 8V and no load, and not manage to keep the voltage up with a load applied. No mystery here.

    TOK ;)
     
  7. vick5821

    vick5821

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    Jan 22, 2012
    Yes, it is 9V battery. I measured it to be 9V but when switch on my circuit, the battery voltage becomes around 6V >< why ? circuit problem ?
     
  8. davenn

    davenn Moderator

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    Sep 5, 2009
    Harald gave you the answer in post #2


    Dave
     
  9. vick5821

    vick5821

    700
    0
    Jan 22, 2012
    I mean any method to overcome this problem ?
     
  10. Harald Kapp

    Harald Kapp Moderator Moderator

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    2,588
    Nov 17, 2011
    No. This is an intrinsic property of batteries.
    Buy a new battery or use another battery with more capacity (e.g. 6*AA cell).
     
  11. gorgon

    gorgon

    603
    24
    Jun 6, 2011
    1. Redesign your circuit, make it use much less current.

    2. Get a new power source, a wallwart or a big battery, as said before.

    TOK ;)
     
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