Dead 18650 batteries

Hey. I've a couple NCR18650B Li-ion batteries that won't charge anymore.
I bought 4 of them and 2 are OK and 2 just won't charge.
Have i done something wrong? Can I fix them or are they stuffed?
They are used in my Zebralight and Armytek torches.
They are not protected as the torches I use requires this.
I bought a charger at the same time, an XTAR VC2 which reviewed well so I hope I'm doing it right?
Any ideas welcome.
Cheers James

@mudgripz or @gadgetman will probably know, I have a couple that are dead but that's cause I used them to much :thumbsup:

Protected cells will often fail when the circuit board dies or the battery voltage gets too low and the protection circuit will not allow them to recharge.

The unprotected cell itself has a 'one time' protection switch under the button cap end that will trip if current gets too high and the cell gets too hot. As a rule once this happens you should bin them. If the switch is reset they often get really hot when you try to recharge them which is not good with such a reactive element as Lithium. Check the voltage across the cell. If it is zero and has open circuit resistance then the switch will have gone. If the voltage is below 3V they are generally gone, though I have recovered some from 2.5V they hold very little charge.

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Originally Posted by gadgetman

Protected cells will often fail when the circuit board dies or the battery voltage gets too low and the protection circuit will not allow them to recharge.

The unprotected cell itself has a 'one time' protection switch under the button cap end that will trip if current gets too high and the cell gets too hot. As a rule once this happens you should bin them. If the switch is reset they often get really hot when you try to recharge them which is not good with such a reactive element as Lithium. Check the voltage across the cell. If it is zero and has open circuit resistance then the switch will have gone. If the voltage is below 3V they are generally gone, though I have recovered some from 2.5V they hold very little charge.

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Anything I can do to stop killing the rest? The ones that are still running are fine. Hold good charge and last. Hard to understand what’s the cause.

Quote:

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Originally Posted by kiwijames

Anything I can do to stop killing the rest? The ones that are still running are fine. Hold good charge and last. Hard to understand what’s the cause.

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Not a lot. If the torch cannot use protected cells then the torch needs to provide adequate protection. Sounds like they don't. How many cells do they take?

Got stable 3.7V in one. 3.5V but drops with the meter on the other to about 3.3V.

Both torches are single cell

Hey. I might have sorted it! The tops were a little crushed and I think they weren’t making good contact with the charger posts.
Fingers crossed but they’re charging now.

Yeah, I ended up bending the +ve terminals on my chargers to get better contact.

I did the same on my charger Gadget, since those laptop batteries have very low "tops" and didn't make good contact. All good now