3A Fuse Not Breaking

Thread Starter

drguildo

Joined Jan 15, 2014
14
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.
 

#12

Joined Nov 30, 2010
18,224
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.
 

R!f@@

Joined Apr 2, 2009
9,918
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.
 

mcgyvr

Joined Oct 15, 2009
5,394
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.
 

Thread Starter

drguildo

Joined Jan 15, 2014
14
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.
 

Alec_t

Joined Sep 17, 2013
14,280
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.
 

BillB3857

Joined Feb 28, 2009
2,570
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.
 

Attachments

inwo

Joined Nov 7, 2013
2,419
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.
 

Thread Starter

drguildo

Joined Jan 15, 2014
14
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.
 

Thread Starter

drguildo

Joined Jan 15, 2014
14
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.
 

mcgyvr

Joined Oct 15, 2009
5,394
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.
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..
 

Alec_t

Joined Sep 17, 2013
14,280
Something inconsistent here:
It's a Morrison's own-brand one which says AA/LR6/1.5V on the side.
When I use a multimeter to measure the voltage on the ends of the wires it's giving out between 8-9V.
If Morrisons are selling 1.5V cells that give out 8-9V, I want a barrow-load :).
 

Thread Starter

drguildo

Joined Jan 15, 2014
14
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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