Very Basic question (Im new) - Why isnt a single AAA battery power able to power a laptop?

Discussion in 'Power Electronics' started by xQuickLearnerx, Oct 1, 2016.

  1. xQuickLearnerx

    Thread Starter New Member

    Oct 1, 2016
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    I know its a silly question but im trying to grasp how everything works, is it basically because the battery does not have enough force (volts) to push the current (electrons) through the circuit?

    Just discovered this site, the learning materials seem great, ill use it along with my adruino starter kit. I'm pretty much learning from scratch here but it really interests me.

    Thanks
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,144
    1,791
    1.5 volts is too low a voltage to power a modern processor, a display, and a hard drive. A typical AC adapter brick will provide 19.5VDC at 4.6 amperes or about 90 watts. If a 1.5 Volt battery was to provide that power it would result in a current of 60 Amperes. That amound of current through the internal resistance of the battery would generate more heat than the battery could handle.
     
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  3. xQuickLearnerx

    Thread Starter New Member

    Oct 1, 2016
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    thanks for that
     
  4. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hi,

    Yes, that was a good answer from Papa :)

    Another view is that with the required current and internal resistance of the battery most of the voltage would be dropped by the internal resistance so there would be none left to 'convert' to the higher voltage.
    Consider a current as low as 1 ampere. With 0.1 ohm internal resistance, we loose 0.1 volt, not too bad yet. Pump that up to 10 amps though, and we are loosing 1v now which is 2/3 of the total votlage of the cell !
    Up a little more, 15 amps, and we are loosing the entire voltage of the cell, 1.5v, so there's nothing left to convert to the required voltage of around 19 or 20 volts.

    Now put 100 of them in parallel and you might have something, but then again it would probably work better to just put many of them in series, and maybe another series set in parallel with that for higher output. The run time would be short anyway though unless you used a lot of batteries.

    A typical AAA cell contains a 'charge' of about 1 Ampere Hour, so if you put a bunch of them in series and the laptop drew 4 amps, the cells 'might' last for 15 minutes, but under that current draw probably less than that, maybe 5 minutes. So you see it is not too economical. Maybe if it was an emergency, but that is something i would want to test BEFORE any emergency came up :)
     
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  5. xQuickLearnerx

    Thread Starter New Member

    Oct 1, 2016
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    Thank you Mr AI, your answer has shown me some holes in my understanding of this, ill have to fill those gaps. Thanks again.
     
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