# 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
16,665
7,313
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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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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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 Thread Starter New Member

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
14
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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.