Simple alkaline battery question

Discussion in 'General Electronics Chat' started by sivart212, Aug 18, 2010.

  1. sivart212

    Thread Starter New Member

    Aug 18, 2010
    3
    0
    Hello,

    I got in an argument with a buddy about using 6 AA batteries opposed to using one 9 volt. He was trying to explain that using the 6 AA's will be harmful to capacitors, will damage them. I told him he's retarded and I've been using 9 volt battery packs instead of a nine volt battery for everything I have that I can with no problems. He then began to say that AA bat's "have more amps than a 9 volt". What is he talking about? mAh? If thats the case I know that. Thats why I use them, they last longer. He continued saying the higher amps would "pop" the capacitors. I have very little knowledge about this and need some smart guys to explain my buddy's seemingly ridiculous assertion.
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Wouldn't matter if you hooked up a power supply with 8,000 amps of capacity, if the circuit is meant to operate off 9V it's only going to draw what it needs from that 9V. However if you increase the voltage] then you could run into trouble.

    Buy him a book on ohm's law and underline I = E/R.

    An even simpler way to explain electronics to someone that doesn't grasp the fundamentals is using an analogy to water pressure and delivery capacity. Given exactly identical water pressure (voltage) will it make any difference f you feed a common lawn sprinler with a 1/2" or 5/8" id hose? (allowing more amperage capability)

    Will a car with an engine capable of producing 500 HP operate any differently from one that can only muster 150 HP when only allowing enough air/fuel mixture into it to cruise at 60 mph? What about all the different CCA ratings on vehicle batteries themselves? You simply have more reserve capacity should you need it.
     
  3. sivart212

    Thread Starter New Member

    Aug 18, 2010
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    Thanks, It made sense to me but him and his cousin put some doubt in my mind. All that I did was increase the capacity. I will make sure to tell him that. Thanks also for the great explanations.
     
  4. sage.radachowsky

    Member

    May 11, 2010
    241
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  5. tom66

    Senior Member

    May 9, 2009
    2,613
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    I've tested it, and a AA battery can deliver about 4.5 amps short circuit, while a 9V battery can deliver about 1.5 amps short circuit. These were Duracell batteries, so quite good brands. Note after the short circuit test the batteries took 5 minutes or so to restore their original voltage and I tested each for ten seconds, they got quite hot!

    A capacitor, when connected, will draw a lot of current to charge up, exponentially reducing to zero. It only depends on the supply resistance, the capacitors ESR and the supply voltage. While a AA battery has less internal resistance than a 9V (generally speaking) it only results in briefly more current being drawn and we are talking about an event lasting less than a millisecond so it's usually not an issue...
     
    Last edited: Aug 19, 2010
  6. sivart212

    Thread Starter New Member

    Aug 18, 2010
    3
    0
    I actually told him that... I got the idea from a youtube video "9 volt battery hack".

    Thanks, I'll continue to use my 6 AA packs. If anyone wanted to see what the look like: http://www.allelectronics.com/make-a-store/item/BH-361/BATTERY-HOLDER-FOR-6-AA-CELLS//1.html
     
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