3A Fuse Not Breaking

Discussion in 'General Electronics Chat' started by drguildo, Jan 15, 2014.

  1. drguildo

    Thread Starter New Member

    Jan 15, 2014
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    I'm a complete beginner so please excuse the ignorance of my post.

    I'm working my way through the Make: Electronics book and one of the first exercises involves fitting a 1.5V AA battery to a battery holder and attaching the leads to a 3A blade fuse.

    Although the book says that the element should break "almost immediately", it doesn't seem to break even after I've held the leads there a number of seconds. Am I doing something wrong?

    One side of the fuse says "iMAXX 3" and the other says "32 V", if that's any help.
     
  2. #12

    Expert

    Nov 30, 2010
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    Are you sure the instructions did not say to attach a D battery or a car battery?
    You're trying to tow a car with a mouse. The AA battery has too much internal resistance to deliver more than 3 amps.
     
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  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    could be your batteries are just old and weak.
     
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  4. drguildo

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    Jan 15, 2014
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  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    1.5V cells cannot break 3A fuse, Mate.
    Not even 9V batteries can do tht.

    But if u try with 12V motor cycle battery, it will.
    But DOING THIS IS DANGEROUS. BATTERY CAN LEAK OR EXPLODE

    DO NOT TRY IT.
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    It all depends on the condition/charge of the battery and its chemistry and internal resistance.
    This will determine its short circuit capacity.
    AA's alone CAN have sufficient short circuit capacity that would cause a fuse to open.

    One datasheet for a battery states 181 milliohms of resistance (internal impedance) and a 1.5V nominal out.
    1.5/.181 = 8.2 Amp short circuit capacity.
     
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  7. drguildo

    Thread Starter New Member

    Jan 15, 2014
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    That's crazy. Why would the person who wrote this book think it could? I mean I believe what you're saying I just can't think why they would put this in the book without at least trying it.
     
  8. drguildo

    Thread Starter New Member

    Jan 15, 2014
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    I just tried with a 9V battery (multimeter said it was delivering around 8-9V) and that didn't do it either.
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Trying to blow the fuse with an AA cell will deplete the cell very quickly if the fuse does not blow immediately. Sounds like a daft experiment to me.
     
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  10. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Told Ya !
    Try the latest 2000mA ones. I don't think it will either

    But a good li-on might
     
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  11. drguildo

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    Jan 15, 2014
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  12. BillB3857

    Senior Member

    Feb 28, 2009
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    Try it with a fully charged Ni-Mh or NiCad. Energizer's data sheet for a AA size shows that it can maintain 3250ma for about 15 minutes before the voltage drops to 0.9v.
     
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  13. inwo

    Well-Known Member

    Nov 7, 2013
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    I'd say it's busted!

    A new AA draws 4 amps thru normal test leads, ammeter, and that type fuse.

    Not enough to blow a slow fuse.
     
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  14. drguildo

    Thread Starter New Member

    Jan 15, 2014
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    So could it be because the only battery I know is brand new is a cheapo brand? It's a Morrison's own-brand one which says AA/LR6/1.5V on the side.
     
  15. alfacliff

    Well-Known Member

    Dec 13, 2013
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    how about the wire size? and the battery holder also has some resistance. too small wire can reduce available current.
     
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  16. drguildo

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    Jan 15, 2014
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    When I use a multimeter to measure the voltage on the ends of the wires it's giving out between 8-9V. I don't really know how this translates to amps.
     
  17. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    It doesn't necessarily.. Its just a measurement of the available voltage.
    I think you skipped some chapters in the book.. Back to the basics..

    basics..then experiments..then more advanced..then more experiments..
    "walk before you run" blah blah blah..
     
  18. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Something inconsistent here:
    If Morrisons are selling 1.5V cells that give out 8-9V, I want a barrow-load :).
     
  19. drguildo

    Thread Starter New Member

    Jan 15, 2014
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    Sorry. The 8-9V was from measuring the output of the 9V battery.
     
  20. drguildo

    Thread Starter New Member

    Jan 15, 2014
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    So how would I go about measuring the amps? There's an "A" mode on my multimeter but I can't seem to get a reading using it.
     
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