i presume this cell is dead

[Barrie]

just got a set of ultrafire protected 18500 1600mAh 3.7 Li-ion from KDs popped them in the charger only one of the two is charging
swapped them over still the same result checked them with a multimeter the one that is not charging is showing zero volts :shakehead

 

[VidPro]

sounds like you have it covered.

you saw the voltage rise on the one that IS charging , just in case you misteak the ever present long holding power of the li-ion for it charging on the charger.

its dead jim, could be the protection failed , but if it was already ZERO from the dealer person, then it may be a bad cell too, bad cell must be carefull about charging.

 

[qwertyydude]

Cut off the protection circuit and see if it'll take a charge. If so just be careful with the battery so you don't over discharge it.

 

[45/70]

Other than a dead cell, it could be that the protection circuit is faulty, or it could be that the protection circuit is tripped, and whatever charger you are using is unable to reset it. A truly dead Li-Ion cell, to my knowledge, rarely has a voltage reading of zero, so you could just be experiencing a tripped circuit. Some chargers just don't have enough "oomph" to reset the circuit.

If you have another charger, see if it'll charge in it. There is some risk involved, but you could also try paralleling the cell with another like cell for a couple seconds (don't hold them together for too long ), and then try it again in the charger, and see if it starts to charge.

Dave

 

[Barrie]

45/70
:thumbsup::twothumbs tried the paralleling and it jumped up to 3.3v and is know charging
thanks Barrie

 

[45/70]

That's great Barrie.

What you should do now, is charge that cell and the good one. Let them sit for a few hours, and then check their voltage. If the cells are new, they should have charged (on a good charger) to 4.20 Volts and still be at that voltage, or maybe (in the real world) at 4.18-4.19 Volts. If the cell in question is much lower than that (or the other cell), you should consider it damaged.

At any rate, it'd be a good idea to keep an eye on that cell for a few charge/discharges, and watch for any inconsistency. If it seems to not hold a charge well or otherwise perform poorly, I wouldn't use it. My best guess is though, that it'll be fine.

Dave