# 18650 voltage question



## adamjh3 (Jun 19, 2010)

Hello all, 

I recently ordered a WF-139 charger and a pair of ultrafire 18650 batteries, and I've run into a bit of an... issue? 

I checked the voltage of the two batteries immediately after receiving them, battery A came back at 3.88V, and battery B came back at 3.89V. I placed both batteries in the charger and plugged the charger in. After plugging it in the indicator light for battery A showed that it was charging, and indicator for battery B showed that it was already fully charged. That didn't seem right to me, so I unplugged the charger and pulled both cells out, thinking it may be an issue with the lights on the charger. So I swapped batteries, put A in B's slot and vice versa, well, the same thing happened, B came back as fully charged, and A indicated it was charging. 

I pulled battery B off the charger, and it still reads 3.89 on my multimeter. I let A run the charging cycle, and pulled it off at the proper time, and it now reads 4.17V.

From what I understand, a Li-ion battery should not exceed 4.2 volts off of the charger, and should not dip below 3.7 volts after it's been discharged. So battery A is good to go, correct? 

But what is going on with battery B? Why is the charger indicating that it is fully charged? Do I have a soon-to-be terrorist cell? 

Thanks,
-Adam :thumbsup:


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## csshih (Jun 19, 2010)

they are protected cells, no? perhaps it's an issue with the protection IC which is not allowing the cell to charge properly.


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## adamjh3 (Jun 19, 2010)

Yes, they are protected, I should have mentioned that.


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## old4570 (Jun 19, 2010)

3.8 ish , is a good storage voltage .... 

check each charge bay ? there ok ? 
If its a protected cell , the safety circuit may be stuck - happens ..

Cure was ???? get a fully charged cell and ??? Id wait for some one who is 100% sure , its been covered before , but I got's the flue and


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## 45/70 (Jun 19, 2010)

adamjh3, there is one thing you might check. You didn't specify what type UlttraFire cell you have, there are many versions. Is it a flat top, or does it have a nipple on the positive end?

If it is a flat top, there is the possibility that the cells + end is not making proper contact with the charger. This would result in the problem you are experiencing. The quality of the shrink wrap application varies a lot on these cells. Some cells might work, and others won't.

Other than that, I'd guess it's a problem with the protection PCB, as csshih suggested. If you have another 18650 charger, you might try charging the cell in it, and see if that works. Otherwise the cell will likely have to be replaced. :sigh:



old4570 said:


> ......but I got's the flue and



Uh, oh! 

Hang in there, old! :thumbsup:

Dave


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## adamjh3 (Jun 19, 2010)

There is a nipple on the positive end, and now that you mention it, it looks like it sits just a tad bit shorter than on the one that charged. 
I do not have another charger to test it on. Is there something I could use as a spacer to see if that works? Or is that not advised? 

This is my first jump into the Li-ion game, and I really don't want to burn my house down! Haha

I knew I should've just purchased some AW's. 

Thanks for the help so far, everyone! And old4570, get yourself some chicken soup and some rest! 

-Adam :thumbsup:


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## 45/70 (Jun 19, 2010)

Well, I have used tiny magnets in such situations. You could stick a paper clip in there maybe, just to see if that makes the cell charge, until you come up with something more suitable. Don't short anything out, of course! 

Dave


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## old4570 (Jun 19, 2010)

Thanks guys ,  , yeah , just getting a little fresh air today , but still not great . Got to keep the fluid intake up . and get some fresh air now and again .
Just makes it real hard to concentrate .

But to trip the PTC , dont you get a good batt and for a bout 1sec or so connect + to + and - to - , and see if the PTC wont trip or untrip as the case may be ??


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## kramer5150 (Jun 20, 2010)

I would just use a paper clip and insert it in there... carefully

My Samsung flat topped cells also have a hard time charging in my WF-139. I have to jiggle them and skew them a little to get the B+ to make contact.


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## adamjh3 (Jun 20, 2010)

Alright, I got it in there and jiggled it around a bit, and it's charging as we speak, I'm keeping a close eye on it. 

I was afraid to mess with it too much without CPF's blessing, as this is my first jump into the li-ion game. I didn't want it going  All my stuff's insured but, y'know, it's such a hassle :laughing:

Anyway, thanks for helping a newbie out, everyone, lovecpf

-Adam :thumbsup:


EDIT to avoid a double post: 

Well, it charged up just fine, light went off and it reads at 4.18V. Thanks again, everyone! 

-Adam :thumbsup:


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## Mikellen (Jul 3, 2010)

I hope its O.K. to post this here. It seemed like an appropriate place to ask
these type of questions.

I just received a second hand Ultrafire 139 charger and an 18650 AW lithium battery. I did not receive an instruction guide with the charger.
This is my first time using rechargeables so I have some questions regarding the charging process.

(1) If I'm only going to charge one battery does it matter which side of the charger the battery should be inserted? 

(2) Will there be a green or red light that either blinks or stays lit to indicate if its charging or done charging? If so can someone please describe what the indicator light will do when charging and when the charge is completed?

(3) Will the charger stop charging when the 18650 cell reaches 4.2V or do I have to keep checking it every so often? 

(4) How long does it typically take to recharge an 18650 cell?

(5) I do have a multimeter and know to not overcharge the cell above 4.2 volts but what is the lowest voltage I should let the cell go down to? 
Is 3.7 volts correct as was stated in an earlier post?

Thanks for any help.


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## HKJ (Jul 3, 2010)

Mikellen said:


> I hope its O.K. to post this here. It seemed like an appropriate place to ask
> these type of questions.
> 
> I just received a second hand Ultrafire 139 charger and an 18650 AW lithium battery. I did not receive an instruction guide with the charger.
> ...



No.



Mikellen said:


> (2) Will there be a green or red light that either blinks or stays lit to indicate if its charging or done charging? If so can someone please describe what the indicator light will do when charging and when the charge is completed?



red=charging
green=done or no battery



Mikellen said:


> (3) Will the charger stop charging when the 18650 cell reaches 4.2V or do I have to keep checking it every so often?



It will stop, but it is best to remove the battery within a few hours.




Mikellen said:


> (4) How long does it typically take to recharge an 18650 cell?



I have not timed it, but it takes a long time, maybe 5 hours.



Mikellen said:


> (5) I do have a multimeter and know to not overcharge the cell above 4.2 volts but what is the lowest voltage I should let the cell go down to?
> Is 3.7 volts correct as was stated in an earlier post?



If the battery has rested a few minutes, 3.7 volt is just about empty. But there are no reason to run the batteries this far down, just charge them whenever you can.


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## Mikellen (Jul 3, 2010)

Thanks HKJ! :thumbsup:


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## 45/70 (Jul 3, 2010)

Mikellen said:


> I just received a _*second hand*_ Ultrafire 139 charger and an 18650 AW lithium battery.......
> 
> ......(3) Will the charger stop charging when the 18650 cell reaches 4.2V or do I have to keep checking it every so often?





HKJ said:


> It will stop, but it is best to remove the battery within a few hours.



How do you know this? Because yours does?

As far as I know, some WF-139 chargers will keep trickling the cell up to as high as 4.50 Volts after the LED turns green!  Mikellen clearly stated that this is a _*second hand*_ charger. There is no way with the information we have, to know how old, or what "generation" this charger is. The only way to determine whether or not it will actually stop charging when the LED turns green, is to check it with a Voltmeter.

Mikellen, I would charge a cell and monitor it closely with your multimeter. If, after the charger indicates charge completion, the cell voltage continues to rise, this indicates that the charger is trickle charging. In this case, you should monitor charging very closely and remove the cell as soon as possible after the LED turns green. 

When charging a Li-Ion cell in a charger which properly terminates charge, generally the cell's voltage will drop 0.01 Volt or so within 10-20 minutes, with all but _*very **new*_ cells. With new cells the voltage may remain at the same level, but in no case should the voltage continue to rise. In any case, regardless of what charger you use, don't charge Li-Ion cells unattended! 

Dave


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## HKJ (Jul 3, 2010)

45/70 said:


> How do you know this? Because yours does?



Because all 3 of mine does.



45/70 said:


> As far as I know, some WF-139 chargers will keep trickling the cell up to as high as 4.50 Volts after the LED turns green!



Not any of the new ones (I believe this includes the last 2 years), but it keeps the cell at 4.2 volt, that is the reason it is a good idea to remove the battery within a few hours.




45/70 said:


> Mikellen clearly stated that this is a _*second hand*_ charger. There is no way with the information we have, to know how old, or what "generation" this charger is. The only way to determine whether or not it will actually stop charging when the LED turns green, is to check it with a Voltmeter.
> 
> Mikellen, I would charge a cell and monitor it closely with your multimeter. If, after the charger indicates charge completion, the cell voltage continues to rise, this indicates that the charger is trickle charging. In this case, you should monitor charging very closely and remove the cell as soon as possible after the LED turns green.



You are right about this (I forgot the old generation of WF139 chargers).
To check this, first measure the charge voltage, without a battery. It must be below 6 volt.
The do a overnight charge and check the final battery voltage, if it is below 4.3 volt the charger is ok (Some will say 4.2 volt, but it is *not* a magic limit where everything above goes  and every thing below is safe).




45/70 said:


> In any case, regardless of what charger you use, don't charge Li-Ion cells unattended!



Or place the charger where a small  will not do any damage, except to the charger.


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## Mikellen (Jul 3, 2010)

O.K., I plugged in the charger and both green lights are constant on. I checked each side with the voltmeter before placing the 18650 battery in and the voltage reads approximately 4.92 volts. 
I then checked the voltage of the 18650 battery and it reads 4.08 volts.
Next I inserted the 18650 battery in the left side of the charger and still both green lights remain on.

Are the steps that I've taken correct?
So does the constant green light indicate that the cell is fully charged even though the cell reads 4.08 volts with the multimeter?

As a test should I really leave the cell in the charger overnight or will 4-5 hours be enough to see if the voltage increased to 4.2 volts?

Thanks.


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## HKJ (Jul 3, 2010)

Mikellen said:


> O.K., I plugged in the charger and both green lights are constant on. I checked each side with the voltmeter before placing the 18650 battery in and the voltage reads approximately 4.92 volts.
> I then checked the voltage of the 18650 battery and it reads 4.08 volts.
> Next I inserted the 18650 battery in the left side of the charger and still both green lights remain on.
> 
> ...



You have one of the new WF-139 charger.

First try moving the battery around a bit and see if the charger change to red light, it might be a bad connection.

The purpose of the test is to verify that the charger does not overcharge the batteries, if you wait a few hours before removing them. With a already charged battery (Green light) 4 to 5 hours are enough.

And do test both channels, they work independently.


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## Mikellen (Jul 3, 2010)

I wiggled the battery around which is in the left side of the charger and the green light is still on. I removed the cell, rechecked the voltage and it still reads 4.08 volts. I now placed it back in the right side of the charger, wiggled it around some and still the green light remains on.

Is it normal for the green light to stay on when the voltage of the cell is below 4.2 volts? 
Would it trickle charge from 4.08 volts to 4.2 volts or should the indicator light be red until 4.2 volts and then turn green?

EDIT: I stuck a paper clip in between the positive terminal of the 18650 cell and the charger and now
the red indicator light is on but it seems to quickly flash to green about every 2 seconds. So the red light stays on for 2 seconds, quickly flashes green for a micro second, then immediately turns back to red for another 2 seconds. This pattern continues. Is this normal? Also is it safe to charge the cell with the paper clip?


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## HKJ (Jul 3, 2010)

Mikellen said:


> I wiggled the battery around which is in the left side of the charger and the green light is still on. I removed the cell, rechecked the voltage and it still reads 4.08 volts. I now placed it back in the right side of the charger, wiggled it around some and still the green light remains on.
> 
> Is it normal for the green light to stay on when the voltage of the cell is below 4.2 volts?
> Would it trickle charge from 4.08 volts to 4.2 volts or should the indicator light be red until 4.2 volts and then turn green?
> ...



Yes, it starts to flash green when the voltage is closing in on 4.2 volt.
The safety of the paper clip depends on the top of the cell, are there any risk the clip might short the + pole to the body of the cell? (AW cells are fully isolated, i.e. no risk).


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