This is not according the guidelines from the LiIon manufacturers, they specify a minimum charge current, when you get below this current the charger must stop charging.
Lol, this never ends
This is where my whole argument points towards - Definitions!
A voltage differential MUST exist between the charger and the cell for a current to flow - Correct!
But the voltage at the terminals of the battery while your charging are EQUAL. i.e. A charger voltage of 4.22 Means, a cell voltage of 4.22 as current is flowing.
If charger voltage was not equal to battery voltage then if we applied/removed a charging current, why do we see a temporary rise and fall in the voltage of the cell?
The only time the voltage can be different is in practice due to the resistance of the wires connecting the output of the charger, and the battery terminals.
In a theoretical parallel circuit, the voltage present at the terminals of the charger EQUAL the voltage at the terminals of the battery. During charge, the voltage at the terminals of the battery will rise to the voltage of the charger - floating voltage.
SO, this is where the water analogy fails... The voltage of the battery terminals during a transfer of charge (i.e. in a charger circuit) is EQUAL to the voltage output of the charger. this doesn't work in the water analogy.
Once this has been established, maybe you can see this from the way I see it?
Its just understanding the Definition and differences between - battery resting voltage vs floating battery voltage under charge
Battery resting voltage = the voltage the cell will be happy to maintain at its level of charge (the "normalised voltage" to ouse your terminology
Floating voltage = the voltage of the cell while your applying a charging current (which as explained earlier, MUST be higher than resting voltage for a current to flow)
I think its the definition above, combined with the following 2 that gave us so much to discuss...........
Max voltage reached = the peak voltage the charger gets to
1) cheaper charger = 4.23 - 2.25
2) hobby charger = 4.20
Cutoff voltage = I this this is where 2 different definitions have been applied in your example (inadvertently?)
1) Cutoff voltage cheap charger = you defined as the resting voltage of the cell (4.20v)
2) Cutoff voltage hobby charger = a floating voltage of (4.20v)
Yes , its not that I dis agree , its that , I was not talking about it , or going there , as it over complicates a simple explanation ..
And you keep going places that I wasnt ?
And as for terminal voltage , again , 4.22v is not an issue for me , and yes I call it insignificant , you obviously have issue with 4.22v and I just dont know what else to say about it .
I have measure terminal voltage , and when doing so you are measuring the voltage from the charger , does this artificially raise the voltage of the battery ? I dont have the scientific equipment to say one way or the other , only that when I pull the battery it reads 2 tenths less . [ Within seconds ]
This is what I have experienced and nothing is going to change that , until I see first hand .
Again I dont see why you need to complicate this or add stuff Im not talking about ...
BAtt Voltage in charger [ cheap chinese ]
So how do you measure 2 voltages at the same time ?
How do you differentiate between the two , as the MM would read the highest voltage ?
If the charger maintains a higher voltage than the battery so that current can flow to the battery , how can the battery be the same voltage ?
So you would need some way to read the internal voltage of the battery whilst monitoring the charger voltage [ I cant do this ]
So what I have done is measure the voltage under charge , + - terminals with the battery in place ...
Then pull the battery and measure the internal voltage , and they were not the same ...
This is my experience ... and you cant change that ...
I forgot I was charging some 16340 ...
So after turning off my computer , I quickly ran my MM over the + - terminals with the battery in place [TR-003]
and what I got [ charging AW 16340 ] was 4.14v to 4.15v [ MM could not make up its mind ]
1second after pulling the AW 16340 , the battery voltage was 4.11v ...
So charger voltage was 3 tenths above battery voltage ?.. I didnt have time to rest the battery and check sag , as Im currently in the school library posting this .
So please excuse me if I stick to what I know , and if I dont give a whats it about true CC/CV .
Im not going to argue over opinion , because everyone has an opinion .
This is my last post on this :
I wanted to talk about charge current rates , butt!
Just an aside your meter won’t have the accuracy required to be able to read the true Voltage.
This article will explain How to Determine Digital Multimeter Accuracy
0.01 with a +- 0.005 variance ... Such is life ...
But measurements are still relevent to within 0.01 +- 0.005 , which is by no means scientific accuracy .
I would love to own a $5000+ Multi meter , it's just not on the cards though .
I learn a lot from these discussions .
Thanks , fellas .
Thats consistent with my understanding, as explained in an earlier post. While a charging current is being applied, you Will see a voltage difference, due to the internal resistance of the cell. Assuming cell internal resistance of 750mOhm, a 0.03v drop means a charging current of 26mA. Fairly reasonable.
what I'm trying to say is a true CC/CV doesn't make a difference, as long as in the end they have the same max voltage reached during charge and terminate at the same current.
I know and agree with most of your thoughts regarding the issue of charging current, nothing wrong there.
The point here is that its incorrect to use battery voltage sag to "prove" it in the way you have, in the context of chargers that both terminate at the same (charge voltage) and current.
All I want is for people to understand that, I'm not going to try to convince you to understand it anymore, the information is above for everyone to read. What I post here is not simply 'opinion'.
[/quote]
I know and agree with most of your thoughts regarding the issue of charging current, nothing wrong there.
The point here is that its incorrect to use battery voltage sag to "prove" it in the way you have, in the context of chargers that both terminate at the same (charge voltage) and current.
All I want is for people to understand that, I'm not going to try to convince you to understand it anymore, the information is above for everyone to read. What I post here is not simply 'opinion'.
[/quote]
Butt , there is the RUB , I said starting current ... I never said they were the same at the end , or the middle
EDIT = I re-read the OP , and I dont know where your getting this from ?
Your making stuff up ! or reading more into things than I intended ... Where is it coming from ?
Now to my comparing a Hobby Charger @ 1A and a cheap Charger [ In this case , the Soshine mentioned earlier ]
Is it the statement above ???????????
I thought I was clear about the charger , and explained it , [ Soshine ] , I said nothing about the Hobby Charger [ as I dont use one to charge batteries ]
Nor that they were the same .... Obviously I fail again !
And I grow tired of this .... You keep saying stuff I never said .
From the first post.
[quote=old4570]
What is the issue ? The hobby charger maintains its charge rate longer , there by charging faster , and also not allowing the battery to normalize during charging .
[/quote]
[quote=old4570]
If you charged your 18650 to 4.2v with the hobby charger and it sags to 4.15v , then it had to be under enough load/stress to sag back to a unstressed state , and the Cheap charger terminates at 4.2v and the battery holds 4.2v , does that tell you that the battery was under far less stress ?
[/quote]
Thanks for the info shared ,really appreciate it
The point here is that its incorrect to use battery voltage sag to "prove" it in the way you have, in the context of chargers that both terminate at the same (charge voltage) and current.
Why ? Is there no increased voltage sag from using higher charge currents ..
And the point is they are not terminating at the same current and voltage [ NOT ] that was what it was all about ,the whole point being their not the same ..
They may start out at the same current but thats about it , OK ,
If you charged your 18650 to 4.2v with the hobby charger and it sags to 4.15v , then it had to be under enough load/stress to sag back to a unstressed state , and the Cheap charger terminates at 4.2v and the battery holds 4.2v , does that tell you that the battery was under far less stress ?
And I was not trying to be precise here , though maybe I should have been , It was not meant to be a direct comparison , but a general one [ my fault ] though when charging a battery with a hobby charger you do set it to 4.2v [ at users discretion ] , and it is the job of the nasty cheap charger to get the battery to 4.2v so excuse me for being too general .
I dare say you are nit picking !
This was never meant to be a scientific paper , but a very general view . With room to move , and allow for variables .
But that may have been lost on you ..
You wish to be precise and exact - then please feel free to post something - rather than nit picking me .
To criticize other is easy :
It is not the critic who counts: not the man who points out how the strong man stumbles or where the doer of deeds could have done better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood, who strives valiantly, who errs and comes up short again and again, because there is no effort without error or shortcoming, but who knows the great enthusiasms, the great devotions, who spends himself for a worthy cause; who, at the best, knows, in the end, the triumph of high achievement, and who, at the worst, if he fails, at least he fails while daring greatly, so that his place shall never be with those cold and timid souls who knew neither victory nor defeat.
Yes, this is absolutely correct, there Will be a voltage sag, and its directly proportional to charge current. Ohms law here.
If we terminate at the same current, the voltage sag will be the same for both chargers. Just basic electrical theory here, no opinion or "feelings", and thats putting the many variables aside too. If we terminate on a different current, then voltage sag will of course be different.
My point was that in the context of chargers that charge at 0.5C (charging an 18650 at 1A is about 0.4C), the starting current and how this is maintained has practically no effect on the final voltage sag. Chargers that gradually reduce charge current toward termination (a CV phase) or chargers that gradual ramp down before termination voltage (on the cheaper charger), between these, in the ball park of 0.5C charge, the effect of voltage sag is significantly dependent on the final termination current.
If we are talking 5C, 3C, 2C, maybe even 1C charges, then sure, we might be able to start considering its effects...
If we are not terminating at the same current and voltage, then your argument is invalid.
We can NOT be fairly comparing 2 chargers on the grounds of voltage sag, if we don't have the same termination current and voltage. Its comparing apples to oranges.
Especially if we are using a voltage sag of 0.05V, when we have differences in termination current and voltage that could amount to 0.05V! (see below example)
[quote=old4570]
And I was not trying to be precise here , though maybe I should have been , It was not meant to be a direct comparison , but a general one [ my fault ] though when charging a battery with a hobby charger you do set it to 4.2v [ at users discretion ] , and it is the job of the nasty cheap charger to get the battery to 4.2v so excuse me for being too general . I dare say you are nit picking ! This was never meant to be a scientific paper , but a very general view . With room to move , and allow for variables . But that may have been lost on you ..
[/quote]
Sure its not a scientific article, and you may not feel the need to define these variables, but here it can be demonstrated that this difference in termination ALONE, can explain the 0.05v "voltage sag", which your claiming to be the result of 'cell abuse'.
(and this is putting aside the inconsistent definition of termination voltage, which I have already demonstrated earlier to add 0.02V to this difference!)
Lets take this example - A charger that trickle charges down to 20mA charge rate, compared to one that terminates at 100mA (which is 1/10C if set to 1A charge), with a battery with an internal resistance of 500mOhms
The charger that trickles to 10mA, will see an immediate voltage sag of (V=IxR) = .02x0.5 = 0.01v (barely measurable with most DMMs )
The charger that terminates at 100mA, will see an immediate voltage sag of (V=IxR) = 0.100x0.5 = 0.05v
Between these 2, we see a 0.04v difference. Remember, this difference, is purely from a difference in termination current, which you have not defined in your original post.
SO unless we can define a termination voltage and current, your data is potentially void, as the above can reasonably more than explain the 'observed' difference in voltage sag. Add that to the variation with your definition of termination voltage, and we have a difference of 0.06V.
Im just bringing to light the fact that your data [voltage sag] is not being applied correctly (no significant relationship between charge current/profile/type and voltage sag in this context), and at the same time, is potentially not accurate either (definition of cutoff voltage).
Nit-picking is defined as - looking for small unimportant errors in order to criticise. What we have here is a Fundamental problem that debunks the whole OP! I don't have the time to troll, Id rather be on the lathe machining up parts, or even just enjoying the rest of BLF. All I wanted was to correct the information in the OP for the benefit of all the members here, and I have tried hard to present my argument with evidence that I have tried to explain clearly. Maybe I'm just not that good at explaining to you, but I don't appreciate the implication when you pull out some philosophical material when there is nothing else to be said. Maybe ill just keep it to myself instead of trying to help where I can.
I give up.
p.s. No hard feelings, and it was certainly fun while it lasted
Oh and heres a charge graph I just did. Predicted voltage drop was 0.019v, actual voltage drop was in that ball park, 0.025v by the end of 4 hours. This is what I call a 4.20V termination, with the cell resting just below 4.18
This one is a 4.23V termination, with a resting voltage of 4.20v.
You have a MM in the charger circuit [ BAtt + - terminals ]
Measuring charger behavior -
When it starts charging , the charger voltage will be higher than the battery voltage , and this will be maintained through the charge cycle to facilitate charging of the battery [ Im only talking cheap dedicated 18650 charger here ]
You will be monitoring the charger voltage , not the battery voltage ...
When the charger stops [ assuming it does ] then you begin to monitor the battery voltage [ depending on charger as I have chargers that read 0volts on completion or when not charging ]
Since you are using the Xtar charger , then you should know this ... "quote" : This one is a 4.23V termination, with a resting voltage of 4.20v.
No its a 4.2v termination , the charger voltage at termination was 4.23 , but the battery was 4.2v ...
In the other example , charger voltage was 4.2v @ termination and battery voltage was ?? and you can see the voltage sag in the graph .... to 4.18v [ was that the hobby charger ]
So all you have done is prove what I have been saying all along , thank you for that .
Since you have proven what I was saying with those nice graphs , I say thank you and good bye to you sir !
So anyone following this thread , please check the graphs , check the sag on the 14500 , in the first 10 minutes there was a nice amount of sag , and then the sag tappers of but continues for some time .. [ My original point ]
As for the Xtar - You cant measure the internal voltage of the battery from the +- terminals during charging because you are measuring the charger voltage !!!!!!
Now everyone have a nice day !
Im really sick of this !
Wow .
Easily one of the most detailed explanations of charging behavior I've ever read .
Thanks for all the information , gentlemen .
Sadness 
The graphs CLEARLY show (what you call) "charger voltage" and the resting voltage.
BOTH graphs show the SAME drop in voltage immediately after the charge current is removed, a result of internal resistance, because both are terminating at a similar C rating, 1/10C or so.
The only difference is one is simply offset upwards by 0.03v. The shape is the same, the voltage difference between "charge" and resting is the same.
OK. so you say we can't measure the voltage of the battery during charge, (i disagree, but this is another story, doesn't change my point here)...
So anyway your saying that were measuring charger voltage when its charging.
(Point 1)
So if the XTAR is showing a "charger voltage" of 4.23v,
Therefore the hobby charger shows a "charger voltage" of 4.20v.
This is according to the graphs provided.
Does anyone disagree with this??? please speak up yes or no.
(Point 2)
The voltage of the cell is represented when there is no charge current applied.
(Point 3)
So according to the XTAR graph, you have defined the "cutoff" as the voltage of the cell when no charge current is applied,
(Point 4)
According to points 2 and 3, and cell voltage is represented in the graph immediately after termination.
(Point 5)
So it is therefore true that the voltage of the cell immediately off a charger is what you call the "cutoff" voltage.
(Point 6)
Therefore, the Hobby charger is "cutting off" at a battery voltage of 4.18v,
(Point 7)
(and regarding the slow gradual drop over 3 hours, if I was to extend the graph for the XTAR, you will also see a slow gradual voltage drop too.)
So in summary - according to your definition of termination voltage being the voltage of the charger at rest, lets go along with that for now.
The XTAR "terminated" at a "battery voltage" of 4.20v,
You described it as a "charger voltage" of 4.23v
Based on this description....
The iCharger therefore "terminated" at a battery voltage of 4.18v,
which you would describe as a "charger voltage" of 4.20v
What isn't there to see in the graph? they "terminated" at DIFFERENT voltages. Regardless of your definition of which voltage you read, as long as there is consistency. You can't simply call one a "charger voltage" and then call the other on a sag when
Whatever the definition of battery resting voltage/charger voltage you want to use. The graphs show VERY clearly, that one has a "charger voltage" of 4.23v, the other only goes to 4.20v.
Or if we call it Battery resting voltage, one is 4.20v, the hobby charger reaches 4.18v.
So all you have done is prove what I have been saying all along , thank you for that .
Since you have proven what I was saying with those nice graphs , I say thank you and good bye to you sir !
I have proven that your definition of cutoff is not consistent.
Now everyone have a nice day !
Im really sick of this !
Ok. So I would like to know everyone thinks of points 1 to 7
- [yes] [no]
- [yes] [no]
- [yes] [no]
- [yes] [no]
- [yes] [no]
- [yes] [no]
- [yes] [no]
Hello guys I am new to this thread
I purchased a Ultra Fire Wf 139 & 4*18650,the problem is the charger cuts at 3.84v, in each cells,but still in green led status for more than +5hrs or so the voltage is still 3.84.Can any one tell if the charger is bad or all the cells.
In the meantime I contacted Dx & they are ready for giving replacement or store credit,but I somehow feel what if the new batch of Wf-139 chargers are all undercharging or the 4*Tf Flames what I got are all defective ones,any one reads this post plz reply and give opinion whatever in ur opinion.
The odds of all the batteries being bad ? are rather long ...
You dont have another charger ? [ to compare too ]
Bad WF139;s - could be , bad batteries , also possible ... Probability sais Charger ..
But without actual testing ..
What charger to get ? TR003 TR001 , I would say Xtar but some forum members have had issue ... So if you put a gun to my head = TR003
Thankx old4570
Very Fast reply,thankx 4 the opinion,Does TR003 over charges ?
2 more thing I noticed.:-
1>When there is no cell in the charger & the green leds are on,the voltage displays in the DMM is 4.96v
2>I opened the charger & can see there are several dry solder cuz the surface is pale,so can it be a reason of undercharging.
Does undercharging damages or lower the power of Lion cells ?