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Old Jun 7, 2007, 6:53 AM   #1
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Please can anyone tell me the significance of the extra small contact between the pair of main contacts on the end of these batteries?

My little battery charger from Maplin (UK electronics & gadgets store) uses the small centre one as its "+" contact, and doesn't use the "+" one on the battery. The centre contact is absent on the Li disposable Cr-V3.

Interestingly, both my CR-V3 rechargeables, one Uniross, and one 'Digital' (Maplin) show, on open-circuit, 3.85V across the main "+" and "-" terminals, and 4.2V across the centre little terminal and the "-" terminal, zero between little terminal and "+" terminal.

Where's that 350mV disappearing? What happens to it when the battery's on load?

Alan T


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Old Jun 7, 2007, 8:33 AM   #2
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I don't know the whole story, but Lithium Ion batteries can explode if not charge correctly so they have an internal protection circuit. My guess is that the extra contact is a means of using this circuit.
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Old Jun 7, 2007, 10:46 AM   #3
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The following is based on my observations my own Z612,my Kodak KLC8000 rechargeable Li-Ions and my non-rechargeable CRV-3s.

The KLC8000 has an end contact and a center contact. Kodak's charger has contacts to mate with those connections only.

The CRV-3 non-rechargeable have twocontacts, one each on the same ends of the two "barrels".

This difference, I suspect is to keep the unwary from attempting to charge non-rechargeable Li batteries thereby avoiding catastophic failures. Whether or not Kodak makes any internal adjustments based on which contacts are in use I don't know.
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Old Jun 7, 2007, 11:47 AM   #4
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ac.smith wrote:
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.........keep the unwary from attempting to charge non-rechargeable Li batteries thereby avoiding catastophic failures.
Brilliant. Yes! Highly necessary, when I think about it.

Mylate father, a retired electrical engineer, rigorously attempted to charge everything he could lay his hands on, resulting in a few messesand minor explosions. If Li batteries had been around at a price he was willing to pay, he'd certainly have tried it unless I got to him first to give him a chemistry lesson.He wouldn't have been defeated by the minor matter of the battery not fitting the charger.

It all started when I was a small boy over 50 years ago, when a colleague of his showed us his children's German train-set like road layout, with little self-propelled model lorries which called now and again at a 'filling station' to have their Zn-C dry cells recharged. So Dad routinely recharged ordinary dry cells long before it was widely known that it would work (slightly).

I still wonder where the o/c voltage drop is coming from.

Thanks,

Alan T


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Old Jun 7, 2007, 9:40 PM   #5
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I enjoy pyrotechnics as much as anybody but preferrably at a distance and definitely not on my workbench or in my house.:lol:
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