Low voltage on 18650 cell

[Bullzeyebill]

I think that the question is will the cell charge up to 4.2 volts, or very close to that. Then see what the drop in voltage is. A healthy LiIon will hold its voltage when fully charged, and if there is a drop it will be very minimal. If there is a severe drop in voltage then yes the LiIon stayed at a low voltage too long.

Bill

 

[Black Rose]

I charged it up this afternoon.

After charge completion, it registered 4.15v (all my cells come off the WF-139 around 4.15 - 4.17v).

Several hours later it has settled to 4.12v.

How long do you normally have to wait to see if a cell is damaged?

 

[Bullzeyebill]

When my good LiIon's charge up to 4.18 (one charger), or 4.2 (other charger) they do not drop more than 0.01 volt. Some of them don't drop voltage at all when fully charged. I try to make it a point to start using them shortly after being charged so they do not start self discharging, however I have had some cells maintain full charge for weeks, or only use about 0.01 volt.

With your problem cell, see if it self discharges any further. If it does then it is not a good candidate for heavy duty use.

Bill

 

[Black Rose]

The cell has lost an additional 0.02v in 24 hours.

I'll continue monitoring it for the rest of the week, but it appears to be wounded.

 

[Black Rose]

The cell continues to self discharge...it's down to 3.97 volts now.

How do you properly dispose of these cells?

 

[seaside]

My good cells are holding voltage quite well. They are like 4.2V off the charger, 4.19V after a week.

Some of my cheap cells act like what you said. 4.16V off the charger, settled down at 4.14V, then the next day it's 4.08V and they seem to hold the voltage at that level.

Holding voltage at certain level is good, but they shouldn't loose that much voltage in a day or two. I do not consider them as complete crap as long as they still are usable. But if they go down below 4V like yours? Hmmm....

I guess there must be a reason why they are so cheap.

 

[Black Rose]

After almost 4 weeks, the cell has self-discharged to 3.82 volts.

 

[old4570]

If you had a battery cycler , id say cycle it a few times ...

Since you dont , throw it in a flashlight and run it on Hi for 5 minutes , let it cool and do it again till you hit sub 3.5v , charge it up , and then run it down , repeat a few times , then charge it up and see what happens ..

self discharge is a common problem for Li-ions , some do it some dont .

I have lots of CR123A rechargeables , some discharge more than others , I think its the trustfires , and they dont seem to discharge at all .

 

[mdocod]

After almost 4 weeks, the cell has self-discharged to 3.82 volts.

IMO, it's done. Hang that cell up.

 

[Black Rose]

Yep. I'm going to check the city's recycling program site and see who takes back lithium based cells and drop it off.

I'm not going to risk playing with a wonky unprotected cell.

 

[DM51]

Li-Ion (LiCo) cells should be shipped/stored at 3.8V – 4.0V. Any cell left sitting at <3.0V for any length of time will suffer permanent damage. The lower the voltage and the longer it has been left there, the worse the damage.

Over-discharged cells can sometimes be recovered. The correct procedure involves slow charging (at ~1/10C) until the cell is safely >3.0V, then charging normally to full, monitoring it constantly for over-heating.

A fully charged Li-Ion cell should charge to 4.2V. If it subsequently loses some of the charge, this indicates a degree of damage or aging. If it cannot hold above 4.0V (~80% charge) it is no longer worth keeping.

 

[AlexLED]

You can hit 0V without doing *much* harm if the cell is recovered in short order. The intensity of the damage has to do with how far away from ideal the voltage the cell is at is combined with how long it has been that way. ...

-Eric

Li-Ion (LiCo) cells should be shipped/stored at 3.8V – 4.0V. Any cell left sitting at <3.0V for any length of time will suffer permanent damage. The lower the voltage and the longer it has been left there, the worse the damage.

Over-discharged cells can sometimes be recovered. The correct procedure involves slow charging (at ~1/10C) until the cell is safely >3.0V, then charging normally to full, monitoring it constantly for over-heating.

A fully charged Li-Ion cell should charge to 4.2V. If it subsequently loses some of the charge, this indicates a degree of damage or aging. If it cannot hold above 4.0V (~80% charge) it is no longer worth keeping.

Ah, very good tips (although have been repeated for some times now...), thanks to you two !

So, I just unwrapped some 18650 from old Laptop packs. Their voltages were somewhere between 0 and 3.8 Volts. I didn't fuss with those below 2 volts, yet, and will probably dispose them of. Those with 2.2 volts and above I charged, starting with 0.1 amps, under close supervision. Didn't get hot and did accept quite Ah till 4.1 volts. They lit up some of my lights fine. :)

I'll check the self-discharge in the next days.

So, can I assume, after a slow-recharge of 2.2 volt cells, they are still fine ? I have no idea how long they have been below 3.5 volt....

 

[SilverFox]

Hello Alex,

When dealing with Li-Ion cells that have been over discharged, I think it would be better not to assume anything...

When you have a few charge/discharge cycles on them, find that they don't have a rapid self discharge rate, and verify that they have at least 80% of their initial capacity, you can then feel more comfortable using them.

Tom

 

[Black Rose]

After almost 4 weeks, the cell has self-discharged to 3.82 volts.

That was posted on May 21, 2009.

It is now June 27, 2009 and the cell is now down to 2.76 volts.

I still haven't gotten around to checking out how to dispose of this cell :whistle:
Is there any danger of this cell doing anything nasty on its own?

 

[Bullzeyebill]

That is truly a damaged cell. Most counties have a depot for hazardous materials that is open most of the time. Check you phone book for an appropriate agency.

Bill

Just noted that you are in Canada. Check your local province?

Bill