Recharging 'Dead li-ion cells'

[RedForest UK]

I just salvaged 6 17670 cells from an old 'dead' toshiba laptop battery pack. They are green sanyo cells with the code: US17670GR written on them.



However, having tested them they come in at between 0.96v and 1.32v. This seems well below the voltage I should recharge them from, but against my better judgement I have begun charging one with my 400mah cottonpickers USB charger with the hope they will quickly 'bounce' up to a decent voltage. The cell is at 3.85v now and still charging, my question is should this cell be ok, and are the others rescuable? Or should I definately not even try charging the others?



Basically, how high are the risks of charging good quality but overdischarged li-ion cells?

 

[Dr. Mario]

That's tricky. Below 3.0 V is considered dead, but I have come across that before too - salvaged few totally dead batteries before. What I'll want to say is that the risks goes up as battery voltage goes down due to the separator "breaching", that is, the Copper shunts will start to develop while the Lithium-ion (LiFePo4 or any miraculous Li-based) batteries sits dead long enough. LiFePo4 battery have cut-off voltage at 2.5V while the vanilla-flavored Li-ion batteries commonly found in the laptops should be cut out at 2.7 - 3.2 Volts depending on "bonding" chemistry, such as Cobalt or Manganese.

You will want to get cheap battery holder and long speaker wires (specifically made for 800W+ car stereo so you would be able to charge the battery without too much losses) so you can charge it from the safe distance, on concrete surface - along with smarter short-circuit protected hobbyist charger set to LiPo settings so it could slowly charge it to the voltage that it should sit at. I haven't done it since I was brave enough to do that the hillbilly way, with my thumb on Anode cap for feeling the warmth so I could tell when I need to quit - that I must not recommend as Li-ion batteries are sometimes known to go bang spectacularly.

So, in other word, if you are not experienced in handling this violate battery chemistry, I would have to recommend; DO NOT CHARGE IT, TOSS IT AND FIND ANOTHER THAT SITS AT 3.0 - 3.2V.

 

[sxl168]

This thread has a lot of info you are probably looking for: http://www.candlepowerforums.com/vb/showthread.php?246699-Tutorial-Laptop-Battery-Pack-18650-Extraction/page3
I have a post about halfway down the page on some tests that can be done, but the rest of the thread should be read also for additional info.

 

[Norm]

Please continue in the thread linked in the post above = Norm