How do I charge a Li Ion cell too low for charge?

ken2400

Enlightened
Joined
Oct 30, 2006
Messages
227
I have some 18650 cells that are not charging.
I assume they will not charge because there voltage is like 1.2
What can I do to charge them?
Could I charge two in series up to 2.1 V each then by them selfs?
I am using a UltraFire WF-139

Thanks
 

SilverFox

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Jan 19, 2003
Messages
12,449
Location
Bellingham WA
Hello Ken,

If your cells have dropped that low, it is probably best just to recycle them. When they sit at low voltages for a period of time, the electrolyte breaks down and the electrodes start to oxidize. When you go to charge them they have a very good chance of exploding in a fire ball.

If you do decide to try to charge them, please do it outside away from people, pets, and anything combustible.

Tom
 

ken2400

Enlightened
Joined
Oct 30, 2006
Messages
227
Kinda what I was thinking.
Will try it outside on Sunday and send back the results.
Thanks

Hello Ken,

If your cells have dropped that low, it is probably best just to recycle them. When they sit at low voltages for a period of time, the electrolyte breaks down and the electrodes start to oxidize. When you go to charge them they have a very good chance of exploding in a fire ball.

If you do decide to try to charge them, please do it outside away from people, pets, and anything combustible.

Tom
 

325addict

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Jan 7, 2009
Messages
959
Location
The Netherlands, Amstelveen
simply take a stabilized power supply with current regulation.

Step 1: trim voltage to 4,1.....4,2V,
Step 2: connect 2 wires to the output-terminals, short them and see how much current flow is. Set it to 0,5A.
Step 3: remove short and connect to battery.

NOTE: one battery at a time!!

You should see a fairly quick increase in voltage, to a little more than 3V initially.
For three to four hours, current should stay at 0,5A with the "Current" LED of your PSU lighting up.
After that, voltage will have risen to 4,1 or 4,2V, and the current starts to fall.

IMPORTANT!!!

When current falls below 50mA, the cell is full.

If this procedure is completely different in your case (eg voltage doesn't ramp up fairly quick, current stays high and constant for more than 5 hours, the final 50mA isn't reached even after having charged for 8 hours or so) then DISCARD the battery, it has been irreversibly damaged then! These batteries are potentially DANGEROUS as they can spit flames and set everything in the immediate surrounding on fire IMMEDIATELY!

I would see this as an experiment to see how much abuse such a battery can take, even after successful "re-animation" I would discard the cell. You can't take ANY risks of burning the house down :shakehead

Timmo.
 
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