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PICList Thread
'[EE] Detection of Alkaline batteries in a charger'
2005\08\15@095047 by alan smith

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Anyone know of a method of detecting if a battery that is inserted into a charger is alkaline or nicad/niMH?

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2005\08\15@100727 by Michael Rigby-Jones

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>-----Original Message-----
>From: spam_OUTpiclist-bouncesTakeThisOuTspammit.edu [.....piclist-bouncesKILLspamspam@spam@mit.edu]
>Sent: 15 August 2005 14:51
>To: Microcontroller discussion list - Public.
>Subject: [EE] Detection of Alkaline batteries in a charger
>
>
>Anyone know of a method of detecting if a battery that is
>inserted into a charger is alkaline or nicad/niMH?

Possibly internal resistance coupled with terminal voltage might be useable.  i.e. a fresh alkaline cell will have a higher terminal voltage than even a freshly charged nicd/nimh.  For simmilar terminal voltages, I would expect the alkaline cell to have significantly higher internal resistance than a nicd/nimh (and nimh has 2-3 times higher internal resistance than nicd).  This would need to be born out by experimental and/or manufacturers data of course.

Of course, telling the difference between a duff nicd/mh and an alkaline cell in this manner may be impossible ;)

Regards

Mike

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2005\08\15@101705 by Wouter van Ooijen

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> Anyone know of a method of detecting if a battery that is
> inserted into a charger is alkaline or nicad/niMH?

apply a square-wave load, observe the voltage difference, estimate
source resistance? AFAIK the source resistance of NiCad is *much* lower
than a compareable alkaline. But you might get introuble distinguishing
a very small NiCad from a large alkaline.

Wouter van Ooijen

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2005\08\15@103905 by olin piclist

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alan smith wrote:
> Anyone know of a method of detecting if a battery that is inserted into
> a charger is alkaline or nicad/niMH?

If it blows up and makes a mess after charging it was an alkaline.

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2005\08\15@122815 by Bob Blick

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> Anyone know of a method of detecting if a battery that is inserted into a
> charger is alkaline or nicad/niMH?

Drive the battery with AC.
Mount a capacitive plate facing the side of the battery.
If the received signal from the plate is in phase with the positive pole,
it's alkaline.

This works because the outer case of alkaline batteries is positive,
nicad/nimh have negative case.

Whether you can get it to work in practice is an excercise left to the
experimenter.

What do you want to bet someone has attempted to patent this idea already?
If not, the piclist will count as prior art, please give me credit :)

-Bob Blick

2005\08\15@134846 by Michael Rigby-Jones

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{Quote hidden}

Bob,

I'm wondering if the very low internal impedance of nicd/mh would cause problems, as the positive and negative would be very closely coupled.

Regards

Mike

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2005\08\15@140647 by David Van Horn

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This works because the outer case of alkaline batteries is positive,
nicad/nimh have negative case.

But carbon-zinc batteries are negative case.




2005\08\15@142735 by Bob Blick

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> But carbon-zinc batteries are negative case.

But carbon-zinc cells are less likely to behave in such a disaterous way
as alkalines when charged.

Cheers,
Bob


2005\08\15@144220 by alan smith

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This relates to a product that can be run off either a rechargeable pack or standard batteries.  I guess another approach is to have two different battery holders.  One haveing a sealed set of rechargeables, the other allowing the user to replace the standard cells.  Then a sensor can detect what pack is plugged in.  That might be the easiest and most foolproof method.

               
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2005\08\15@145408 by Michael Rigby-Jones

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>-----Original Message-----
>From: EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu [piclist-bouncesspamspam_OUTmit.edu]
>Sent: 15 August 2005 19:42
>To: Microcontroller discussion list - Public.
>Subject: RE: [EE] Detection of Alkaline batteries in a charger
>
>
>This relates to a product that can be run off either a
>rechargeable pack or standard batteries.  I guess another
>approach is to have two different battery holders.  One
>haveing a sealed set of rechargeables, the other allowing the
>user to replace the standard cells.  Then a sensor can detect
>what pack is plugged in.  That might be the easiest and most
>foolproof method.

This is exactly what Kodak did in a DX3700 camera I bought years ago.  The special (i.e. expensive) Kodak battery pack was simply 2 AA NiMh cells with a simple plastic sleeve that operated a switch in the cammera.  When they died, I simple removed the sleeve and fitted it over a couple of new high capcity cells.  Not much good for a "universal" type charger though.

Regards

Mike

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2005\08\15@190229 by Dwayne Reid

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At 12:42 PM 8/15/2005, alan smith wrote:
>This relates to a product that can be run off either a rechargeable pack
>or standard batteries.  I guess another approach is to have two different
>battery holders.  One haveing a sealed set of rechargeables, the other
>allowing the user to replace the standard cells.  Then a sensor can detect
>what pack is plugged in.  That might be the easiest and most foolproof method.

One piece of consumer equipment I worked on years ago (Sony? don't
remember) did something similar: the charging contacts made connection
through a cut-away portion of the cell's outside insulating sleeve.  Seemed
like a workable solution at the time.

In more modern times, the battery pack connection for RTS wireless intercom
belt packs (division of Telex) have 3 contacts.  The battery sled intended
for alkaline cells uses only two of those contacts; the sealed rechargeable
battery packs have all three contact positions populated.  I haven't looked
inside but I'm guessing the 3rd contact is to a thermistor and provides
both rechargeable pack identification as well as cell temperature.

dwayne

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2005\08\16@012917 by Russell McMahon

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>>Drive the battery with AC.
>>Mount a capacitive plate facing the side of the battery.
>>If the received signal from the plate is in phase with the
>>positive pole, it's alkaline.
>>
>>This works because the outer case of alkaline batteries is
>>positive, nicad/nimh have negative case.


A superb idea. But do note that Zinc-Chloride and leClanche (much the
same but different) have negative outer shells.

I built a toaster-tester once that determined if one of the two
switches in each main slead was stuck on (as some were). It measured
capacitance between the two mains pins. joined together and the ground
pin. Stuck switch gave far higher capacitance.

.

       RM


2005\08\17@104332 by Howard Winter

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On Mon, 15 Aug 2005 10:39:13 -0400, Olin Lathrop wrote:

> alan smith wrote:
> > Anyone know of a method of detecting if a battery that is inserted into
> > a charger is alkaline or nicad/niMH?
>
> If it blows up and makes a mess after charging it was an alkaline.

However if it blows up and wrecks the room, it was Lithium!  :-)

Cheers,


Howard Winter
St.Albans, England


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