Hobby Charger VS Cheap Chinese Charger [ charger behavior ] some thoughts

Batteries and Chargers Rechargeable Batteries
19

hey old is the imax b6 still a one shot deal with calibration

20

If mem serves , its a one shot thing for balance charging , for voltage calibration , as many times as it takes ...

21

I haven't fully read the following posts, but I Disagree with the OP on several points

  1. How Resting Voltage works, vs the way a cell is treated
  2. The overall concept of why true (CC/CV) vs emulated CC/CV is better
Lets start with some battery stuff.

Termination voltage. All chargers should be trying to aim for 4.20V finish, without Ever exceeding this voltage (we all agree here). A true CC/CV charger will have voltage measurement systems in place to monitor this voltage, and will always stay below this. Consequently, achieving a cell resting voltage of 4.20V is very difficult when you cannot exceed this. This is because the cell has an internal resistance (which as the old points out, applies in both charging and discharging states).

Charging - CC/CV technique.
The CC part is where a cell can be charged at its recommended charging current, without exceeding the max charge current. In this part of the cycle, the voltage rises. Until which time it reaches 4.20V per cell, then the charger will reduce current to the cell to maintain 4.20V. This is all governed by the internal resistance of the battery.

SO, if we applied 1.0A charging current to a cell at 3.00V, its internal resistance of 500mOhms will result in the voltage of the cell to Rise under charging load. Based on Ohms Law, this setup will result in a 0.5V increase, and the cell voltage rises to (3.00 + 0.50 = 3.50V). Once we remove the charge current the voltage will drop back down.

Lets say this cell now reaches a resting voltage of 3.70V. The same 1.0A charging current, will give the same 0.50V increase, so the voltage of the cell under the charging current will now reach (3.70 + 0.50 = 4.20V)

Beyond this, the resting voltage of the cell will continue to increase past 3.70V, but the actual voltage at the cell due to the charging current will continue to rise past 4.20V. So we must now Reduce the current to maintain a maximum cell voltage of 4.20V. At this point, we say the charger transitions from the CC mode to the CV mode.

If the cell now has a resting voltage of 4.00V, there is a certain amount of current that we can apply that will not exceed the charging voltage of 4.20V. A charge current of 0.40A will cause a voltage increase of 0.20V, and so at this instant, we can only be applying 0.40A charge. Our charger is slowing down so as to not exceed 4.20V, but accordingly will be give the cell less and less energy.
The key to this is --> as the charging current drops, the difference between cell resting voltage and cell charging voltage will get closer and closer, but will take longer and longer because were giving the cell less charging power.

SO... To achieve a resting voltage of 4.20V, if we extrapolated the graphs, we will see that as voltage difference tends to 0, charging current also tends to 0. What does this mean? - to get a resting voltage of 4.20V, we need our charger to charge for an infinite amount of time.

So again, lets put this down simply.
Because of the Internal Resistance of the battery, The ONLY way to achieve a resting voltage of 4.20V is to
a) While holding a charge voltage of 4.20V, apply a current that tends to 0mA, i.e. charge for an infinitely long time
b) Allow the charge voltage to go ABOVE 4.20V and terminate charge at a given current so that the cell resting voltage drops down to 4.20V

The number one rule of a True CC/CV charger is that it Never exceeds 4.20V, and because it usually terminates at a current above 0mA, (usually 1/10 charge rate), it CANNOT EVER give you a resting voltage of 4.20V.

So how does our budget a charger achieve a resting voltage of 4.20V??? Simple - It either charges for infinite amount of time, or it has allowed the cell voltage to exceed 4.20V
(remember, our cell protection circuits protect for over-voltage between 4.25 to 4.35V. It can stop huge over charging due to wrong chargers etc.. but it won't stop regular insidious overcharging with less accurately regulated chargers)

2) CC/CV charging profiles are the Ideal charging profile for lithium. Lithium cells that we commonly use, charge to a fully charged voltage of 4.20V. A cell at this voltage is safe, and this voltage Must not be exceeded at any time.

The CC part is where a cell can be charged at its recommended charging current, without exceeding the max charge current. In this part of the cycle, the voltage rises. Until which time it reaches 4.20V per cell, then the charger will reduce current to the cell to maintain 4.20V. This is all governed by the internal resistance of the battery.

*A budget charger doesn't have a true CC/CV profile, it only roughly emulates it, reducing current much earlier than necessary before the cell has even reached 4.20V. This is effectively means during the time in which a charger Can be very safely delivering charge power, the budget charger is already backing off. This period is also where charging time could be significantly reduced.
At the last part of charging, the CV phase, where the overcharging is done, the budget charger keeps going and as demonstrated above, Must be allowing a slight over-charge to achieve a 4.20V resting voltage.

So what does the budget charger give us? A Slower charge because its backing off too early, but an over-charged cell because its not truly regulating to a maximum 4.20V.

A resting voltage of 4.17 is therefor MUCH healthier than a resting voltage of 4.20V.

Lets have another example,
It is true that this voltage differential (and voltage settling) will occur with hobby chargers, simply because they usually terminate charge at 1/10 charge rate. A 0.5A charge will terminate at 50mA, and accordingly with a internal resistance of 500mOhms, this equates to a voltage increase of 0.02V.Therefore a charge that terminates at 4.20V, 0.05mA, will give a resting voltage of 4.18V.
If your budget charger that terminates at 50mA, gives a resting voltage of 4.20V, it must have terminated at 4.22V.
22

Ok the spaces have been lost in my post... (added spaces another way, formatting issue/quirk happened there due to a little glitch in the automatic spacing after playing around with dot points etc...)

Anyway, What I disagree with in particular are the arguments in the OP describing the "stressing" of a cell during charge, and "normalisation" of a cell.

Normalisation as I understand your description to mean, is describing how the resting voltage of the cell is able to stay at 4.20V following a charge. I.e. the difference between the charging voltage and the resting voltage is minimised. It was also mentioned that this will take an hour.

Your proof of "stressing" a cell argues that a cell that rests at 4.20V following a charge on the budget charger is proof that there is no voltage drop and therefore the lower charge current has been more gentle on the cell.

What the charger does to get the cell up into the 4.20V region does not influence the final resting voltage, simply because the hobby charger has a CV phase, which has the primary goal of allowing the cell to "normalise". Because of the high internal resistance of cells we normally use, even the hobby charger spends more than half its time in the CV phase, and it is during this time that current is reduced to the termination current. With a current that tends toward the same termination current, it will give no difference in settling time and the amount of settling off the charger. Cell health is a bigger determinant here, but thats another story.
So as demonstrated in my previous post, achieving a resting voltage of 4.20V is only possible if overcharged, or charged for an infinite about of time, and is additionally not relevant to the charging profile prior to the CV phase.
It was also mentioned was that a hobby charger charges too fast, 1A charging rate for a 16340 is too high for most cells, but at least with a hobby charger it can be set to any current, 100mA, 300mA, 500mA. 1A is not the only current that hobby chargers can charge at, it is up to the user to set the current.
23

Very informative and useful , okwchin . Thanks .

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No time for a complete reply ,,, [ school ]

But several miss quotes , and errors to reply to as time permits ..

25

Ok the spaces have been lost in my post... (added spaces another way, formatting issue/quirk happened there due to a little glitch in the automatic spacing after playing around with dot points etc...)

Anyway, What I disagree with in particular are the arguments in the OP describing the "stressing" of a cell during charge, and "normalisation" of a cell.?? Discharging a cell imparts stress as does charging , this stress then manifests itself as cell degradation ,

as for normalization , think of it as the battery at rest , and at the voltage its going to maintain [ not accounting for self discharge ]

Normalisation as I understand your description to mean, is describing how the resting voltage of the cell is able to stay at 4.20V following a charge. I.e. the difference between the charging voltage and the resting voltage is minimised. It was also mentioned that this will take an hour.

Your proof of "stressing" a cell argues that a cell that rests at 4.20V following a charge on the budget charger is proof that there is no voltage drop and therefore the lower charge current has been more gentle on the cell.

What the charger does to get the cell up into the 4.20V region does not influence the final resting voltage, simply because the hobby charger has a CV phase, which has the primary goal of allowing the cell to "normalise". Because of the high internal resistance of cells we normally use, even the hobby charger spends more than half its time in the CV phase, and it is during this time that current is reduced to the termination current. With a current that tends toward the same termination current, it will give no difference in settling time and the amount of settling off the charger. Cell health is a bigger determinant here, but thats another story.
You did not understand !
Cheap charger , battery comes of at 4.2v and maintains 4.2v = I think of that as low stress ...
Battery comes of at 4.2v , and sags to 4.15 or worse , due to charge current being high = I call that more stress ...
This was all about Hobby chargers being used at 0.8A to 1A ,
Things change if you charge at 500mA or lower .
Many argue the hobby charger is better because it charges faster [ Higher current ] , my point is , there is a downside to this argument
Hobby charger is safer and causes less battery degradation , again , can you have your cake and eat it ?
So as demonstrated in my previous post, achieving a resting voltage of 4.20V is only possible if overcharged, or charged for an infinite about of time, and is additionally not relevant to the charging profile prior to the CV phase. I dis agree , I have several chargers that charge to 4.2 exactly , and with a good battery it will maintain 4.2v [ the worse the cell = higher internal resistance - well they tend to sag ]
It was also mentioned was that a hobby charger charges too fast, 1A charging rate for a 16340 is too high for most cells, but at least with a hobby charger it can be set to any current, 100mA, 300mA, 500mA. 1A is not the only current that hobby chargers can charge at, it is up to the user to set the current. 16340 ????? only mentioned them as a recent discharge test found several badly degraded cells that did not show from normal procedures [ MM ] .

I haven't fully read the following posts, but I Disagree with the OP on several points Hmm didn't read it , but felt the need = Nice !

  1. How Resting Voltage works, vs the way a cell is treated
  2. The overall concept of why true (CC/CV) vs emulated CC/CV is better Is this gospel ? or merely the most accepted ?
Lets start with some battery stuff.

Termination voltage. All chargers should be trying to aim for 4.20V finish, without Ever exceeding this voltage (we all agree here). A true CC/CV charger will have voltage measurement systems in place to monitor this voltage, and will always stay below this. Consequently, achieving a cell resting voltage of 4.20V is very difficult when you cannot exceed this. This is because the cell has an internal resistance (which as the old points out, applies in both charging and discharging states).

Charging - CC/CV technique.
The CC part is where a cell can be charged at its recommended charging current, without exceeding the max charge current. In this part of the cycle, the voltage rises. Until which time it reaches 4.20V per cell, then the charger will reduce current to the cell to maintain 4.20V. This is all governed by the internal resistance of the battery.

SO, if we applied 1.0A charging current to a cell at 3.00V, its internal resistance of 500mOhms will result in the voltage of the cell to Rise under charging load. Based on Ohms Law, this setup will result in a 0.5V increase, and the cell voltage rises to (3.00 + 0.50 = 3.50V). Once we remove the charge current the voltage will drop back down.

Lets say this cell now reaches a resting voltage of 3.70V. The same 1.0A charging current, will give the same 0.50V increase, so the voltage of the cell under the charging current will now reach (3.70 + 0.50 = 4.20V)

Beyond this, the resting voltage of the cell will continue to increase past 3.70V, but the actual voltage at the cell due to the charging current will continue to rise past 4.20V. So we must now Reduce the current to maintain a maximum cell voltage of 4.20V. At this point, we say the charger transitions from the CC mode to the CV mode.

If the cell now has a resting voltage of 4.00V, there is a certain amount of current that we can apply that will not exceed the charging voltage of 4.20V. A charge current of 0.40A will cause a voltage increase of 0.20V, and so at this instant, we can only be applying 0.40A charge. Our charger is slowing down so as to not exceed 4.20V, but accordingly will be give the cell less and less energy.
The key to this is --> as the charging current drops, the difference between cell resting voltage and cell charging voltage will get closer and closer, but will take longer and longer because were giving the cell less charging power.

SO... To achieve a resting voltage of 4.20V, if we extrapolated the graphs, we will see that as voltage difference tends to 0, charging current also tends to 0. What does this mean? - to get a resting voltage of 4.20V, we need our charger to charge for an infinite amount of time.

So again, lets put this down simply.
Because of the Internal Resistance of the battery, The ONLY way to achieve a resting voltage of 4.20V is to
a) While holding a charge voltage of 4.20V, apply a current that tends to 0mA, i.e. charge for an infinitely long time
b) Allow the charge voltage to go ABOVE 4.20V and terminate charge at a given current so that the cell resting voltage drops down to 4.20V
Charge voltage yes - not necessarily battery voltage
The number one rule of a True CC/CV charger is that it Never exceeds 4.20V, and because it usually terminates at a current above 0mA, (usually 1/10 charge rate), it CANNOT EVER give you a resting voltage of 4.20V.

So how does our budget a charger achieve a resting voltage of 4.20V??? Simple - It either charges for infinite amount of time, or it has allowed the cell voltage to exceed 4.20V
(remember, our cell protection circuits protect for over-voltage between 4.25 to 4.35V. It can stop huge over charging due to wrong chargers etc.. but it won't stop regular insidious overcharging with less accurately regulated chargers)

2) CC/CV charging profiles are the Ideal charging profile for lithium. Lithium cells that we commonly use, charge to a fully charged voltage of 4.20V. A cell at this voltage is safe, and this voltage Must not be exceeded at any time.

The CC part is where a cell can be charged at its recommended charging current, without exceeding the max charge current. In this part of the cycle, the voltage rises. Until which time it reaches 4.20V per cell, then the charger will reduce current to the cell to maintain 4.20V. This is all governed by the internal resistance of the battery.

*A budget charger doesn't have a true CC/CV profile, it only roughly emulates it, reducing current much earlier than necessary before the cell has even reached 4.20V. This is effectively means during the time in which a charger Can be very safely delivering charge power, the budget charger is already backing off. This period is also where charging time could be significantly reduced. So it is less stressful , and gentler on the battery ...
At the last part of charging, the CV phase, where the overcharging is done, the budget charger keeps going and as demonstrated above, Must be allowing a slight over-charge to achieve a 4.20V resting voltage.



So what does the budget charger give us? A Slower charge because its backing off too early, but an over-charged cell because its not truly regulating to a maximum 4.20V.

A resting voltage of 4.17 is therefor MUCH healthier than a resting voltage of 4.20V.

Lets have another example,
It is true that this voltage differential (and voltage settling) will occur with hobby chargers, simply because they usually terminate charge at 1/10 charge rate. A 0.5A charge will terminate at 50mA, and accordingly with a internal resistance of 500mOhms, this equates to a voltage increase of 0.02V.Therefore a charge that terminates at 4.20V, 0.05mA, will give a resting voltage of 4.18V.= The issue was , folks buy hobby chargers to be safer , and to charge cells so as not to damage them , and then turn around and charge @ higher current rates that [ my opinion ] stress the batteries more than the cheap chargers they are avoiding , and at the worst time , closer to completion . [ This is up to the individual ]
And if you charge at a lower rate , then is it faster or better ? Me thinks not . [ Thats me ]
If your budget charger that terminates at 50mA, gives a resting voltage of 4.20V, it must have terminated at 4.22V. = Well the charger voltage may be 4.22 , this does not mean that the battery voltage is the same , as these chargers usually run 2 tenths above batt voltage . So if it terminates at 4.22 , then the actual charger voltage would have been more like 4.24 4.25v
Will get to this as time permits :

If your budget charger that terminates at 50mA, gives a resting voltage of 4.20V, it must have terminated at 4.22V. Lets start here ....

First , 4.22v is nothing , insignificant voltage to worry about , and is often touted as something for people to worry about . [ Why do people bring this up ? I dont know ]

If its something about stressing older cells , ?? . Most of the chargers I have are sensitive to the internal resistance of the battery , so when nearing completion , a cell with higher internal resistance will terminate at a lower voltage , [ Tr003 , WF-139 , WF-188 , Xtar to name a few ] and there are some charger that will try very hard to bring the battery to 4.2v such as the Soshine and TR-001 , but this is and will be about buyers knowing or educating themselves .

So rather than trying to scare people , we should be trying to educate them .

Also dont forget , @ 50mA , its a very gentle charge rate , gentle = low stress , and yes it takes a while .

[ Im out of time this morning - so maybe 8 hours from now ]

Cheap charger behavior , now most cheap chargers do the pulse charge method ..

What that is it , charges , stops charging to check the battery then continues to charge .

Now when it stops to check the batt , the charger than is able to adjust voltage [ of the charger and charge current ] ..

Now while the charger does indeed have a higher charge voltage [ lets say 4.22v near termination ] it does not mean that this is the voltage of the battery [ one needs to understand this ], and because it stops and starts , when the battery reaches 4.2v , it should [ should ] stop charging .

Now as to the termination voltage of the battery , two factors are involved , the charger [ obviously ] as well the battery ..

Depending on the internal resistance , and the sensitivity of the charger to such , can have a contributing effect on termination voltage ..

A battery in rerally good condition may terminate 4.22v or 4.21v and hold said voltage .. Because its a good quality battery ..

A battery in not so good shape may terminate 4.17v in the very same charger , and a cell on its last legs could very well go 4.2v ...and hold the voltage .

Its important to understand there are so many variables involved .

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Clearly that's too much to read ..

Can you guys just meet at Cutter and have it out in the parking lot ..?

Bring your lights with you ...Winner take all

need to subscribe to this thread

27

Having a bad day ?

Banter is good , when people take pot shots , gives you a chance to plug the holes !

28

Hehe, more fun!

29

Ok the spaces have been lost in my post... (added spaces another way, formatting issue/quirk happened there due to a little glitch in the automatic spacing after playing around with dot points etc...)

Anyway, What I disagree with in particular are the arguments in the OP describing the "stressing" of a cell during charge, and "normalisation" of a cell.?? Discharging a cell imparts stress as does charging , this stress then manifests itself as cell degradation

Agreed here, the process of charging applies a stress to the cell.


as for normalization , think of it as the battery at rest , and at the voltage its going to maintain [ not accounting for self discharge ]

Ok, so as described below - referring to the voltage the cell is able to maintain following a charge. 4.20V is possible after a charge that tapers to 0mA at 4.20v, so that we have managed to maximise energy put into the cell for a given voltage, defined as true equalisation of the voltage between the charger and the battery.

Normalisation as I understand your description to mean, is describing how the resting voltage of the cell is able to stay at 4.20V following a charge. I.e. the difference between the charging voltage and the resting voltage is minimised. It was also mentioned that this will take an hour.

Your proof of "stressing" a cell argues that a cell that rests at 4.20V following a charge on the budget charger is proof that there is no voltage drop and therefore the lower charge current has been more gentle on the cell.

What the charger does to get the cell up into the 4.20V region does not influence the final resting voltage, simply because the hobby charger has a CV phase, which has the primary goal of allowing the cell to "normalise". Because of the high internal resistance of cells we normally use, even the hobby charger spends more than half its time in the CV phase, and it is during this time that current is reduced to the termination current. With a current that tends toward the same termination current, it will give no difference in settling time and the amount of settling off the charger. Cell health is a bigger determinant here, but thats another story.
You did not understand !
Cheap charger , battery comes of at 4.2v and maintains 4.2v = I think of that as low stress ...
Battery comes of at 4.2v , and sags to 4.15 or worse , due to charge current being high = I call that more stress ...
I Agree that you will see 4.15V if you pulled the cell off a hobby charger that was charging at 1A 4.20V. Thats if you terminate from charge at 1A. The CV phase of the hobby charger WILL allow the cell to almost "normalise" and the result will be the same because both terminate at 50mA in the end.
Can you confirm that you have SEEN your hobby charger, set to 1A charge rate, with a termination of 50mA, charging the Same cell give you a resting voltage of 4.15V, while the Same cell in the budget charger with the same 50mA cutoff, will allow the cell to rest at 4.20V (and also never exceed 4.20V during charge)? (assuming there is no trickle charge, because thats not a true cutoff)

This was all about Hobby chargers being used at 0.8A to 1A ,
Things change if you charge at 500mA or lower .
between 1A and 0.5A, the charging rate is still within 1-2C of the battery, and has no significant effect on the final resting voltage because there is a CV phase of the charging cycle that covers 30-60 minutes, this is what the CV phase does. It allows reducing current flow to allow the differential between the charge load voltage and unloaded voltage to equalise.

Many argue the hobby charger is better because it charges faster [ Higher current ] , my point is , there is a downside to this argument
Hobby charger is safer and causes less battery degradation , again , can you have your cake and eat it ?
A hobby charger can charge at a higher current, and I do agree that this can cause higher battery degradation. We have to be comparing at the same current. For the SAME initial CC charging current, the hobby charger WILL be faster, without having to use higher charge currents.
So as demonstrated in my previous post, achieving a resting voltage of 4.20V is only possible if overcharged, or charged for an infinite about of time, and is additionally not relevant to the charging profile prior to the CV phase. I dis agree , I have several chargers that charge to 4.2 exactly , and with a good battery it will maintain 4.2v [ the worse the cell = higher internal resistance - well they tend to sag ]
Theoretically speaking, it is simply Not possible. You can NEVER achieve 100% equalisation. Power will flow from the charger to the higher voltage potential to the lower voltage potential, rate limited by resistance. The current flow is determined by the difference in voltage, divided by the resistance. Assuming resistance is constant (internal resistance of the battery/circuit), the only variable here is Voltage difference.
Its like having a ribbon. You can only ever cut the ribbon in half, and half again. If you keep cutting the ribbon in half, you will keep on getting closer and closer to the end, but you can NEVER reach the end, only half as close each time.
If power is transferred, and we half the voltage difference, we half the current flow. We can keep doing this for infinity time, but we will Never reach the end. This is what I mean by, we can never achieve true equalisation. Thats why a cutoff current exists, a point at which we accept that the ribbon is short enough to the end to be called "the end of charge".
The only way is to cheat, by taking bigger steps, which is possible with a higher voltage potential (overcharging a little at the end say 0.02v. This can allow us to hit the end of the ribbon.

You can't deny the theory, the only way to achieve a true 4.20v resting is to charge for infinity time, or overcharge slightly.

Ok, so if the above is true, how did you still measure 4.20V in both occasions? Its theory vs practice... can we actually measure the differences?
Lets take another approach to this difference in view with another calculation. If we have a cell with 250mOhm resistance. To achieve a voltage differential of 0.005v (the largest difference that will read the same on a 0.01v accuracy multimeter), you need the charging current to drop to 20mA. If your charger terminates at 20mA, the differential between the charge load voltage, and unloaded resting cell voltage is less than 0.005V, and therefore can read as the same measurement.
It is therefore reasonable to say that a 20mA cutoff is very achievable (especially if the cell is trickled for an hour or two), and give the same reading on a DMM that reads voltage to an accuracy of 0.01v.
Whats my point here? The voltage differences with these low cutoffs are very close to allowing us to have Very well equalised cells that are so close to 4.20v, that the measuring equipment may not allow us to appreciate that there is a differential, but theoretically speaking, it Must exist.
Again, both the hobby charger, And the budget charger, Both can achieve the same finish if they both cutoff as the same current. The size of the steps you took when you were cutting the ribbon at the start do not affect how short you can end up getting the ribbon. (unless you seriously over do the charging rate - like 5-10C rates... but thats not the point of this exercise)

It was also mentioned was that a hobby charger charges too fast, 1A charging rate for a 16340 is too high for most cells, but at least with a hobby charger it can be set to any current, 100mA, 300mA, 500mA. 1A is not the only current that hobby chargers can charge at, it is up to the user to set the current. 16340 ????? only mentioned them as a recent discharge test found several badly degraded cells that did not show from normal procedures [ MM ] .



I haven't fully read the following posts, but I Disagree with the OP on several points Hmm didn't read it , but felt the need = Nice !

Yes, I did not want to say I had read the other members posts yet, but I did read your post, you need to read that sentence again.

  1. How Resting Voltage works, vs the way a cell is treated
  2. The overall concept of why true (CC/CV) vs emulated CC/CV is better Is this gospel ? or merely the most accepted ? CC/CV charging profiles are prescribed by the battery manufacturers as the recommended charging profiles, according to battery data sheets. Of course, there is no problem in charging slower, but there is also no problem in charging at a lower CC rate either.
Lets start with some battery stuff.

Termination voltage. All chargers should be trying to aim for 4.20V finish, without Ever exceeding this voltage (we all agree here). A true CC/CV charger will have voltage measurement systems in place to monitor this voltage, and will always stay below this. Consequently, achieving a cell resting voltage of 4.20V is very difficult when you cannot exceed this. This is because the cell has an internal resistance (which as the old points out, applies in both charging and discharging states).

Charging - CC/CV technique.
The CC part is where a cell can be charged at its recommended charging current, without exceeding the max charge current. In this part of the cycle, the voltage rises. Until which time it reaches 4.20V per cell, then the charger will reduce current to the cell to maintain 4.20V. This is all governed by the internal resistance of the battery.

SO, if we applied 1.0A charging current to a cell at 3.00V, its internal resistance of 500mOhms will result in the voltage of the cell to Rise under charging load. Based on Ohms Law, this setup will result in a 0.5V increase, and the cell voltage rises to (3.00 + 0.50 = 3.50V). Once we remove the charge current the voltage will drop back down.

Lets say this cell now reaches a resting voltage of 3.70V. The same 1.0A charging current, will give the same 0.50V increase, so the voltage of the cell under the charging current will now reach (3.70 + 0.50 = 4.20V)

Beyond this, the resting voltage of the cell will continue to increase past 3.70V, but the actual voltage at the cell due to the charging current will continue to rise past 4.20V. So we must now Reduce the current to maintain a maximum cell voltage of 4.20V. At this point, we say the charger transitions from the CC mode to the CV mode.

If the cell now has a resting voltage of 4.00V, there is a certain amount of current that we can apply that will not exceed the charging voltage of 4.20V. A charge current of 0.40A will cause a voltage increase of 0.20V, and so at this instant, we can only be applying 0.40A charge. Our charger is slowing down so as to not exceed 4.20V, but accordingly will be give the cell less and less energy.
The key to this is --> as the charging current drops, the difference between cell resting voltage and cell charging voltage will get closer and closer, but will take longer and longer because were giving the cell less charging power.

SO... To achieve a resting voltage of 4.20V, if we extrapolated the graphs, we will see that as voltage difference tends to 0, charging current also tends to 0. What does this mean? - to get a resting voltage of 4.20V, we need our charger to charge for an infinite amount of time.

So again, lets put this down simply.
Because of the Internal Resistance of the battery, The ONLY way to achieve a resting voltage of 4.20V is to
a) While holding a charge voltage of 4.20V, apply a current that tends to 0mA, i.e. charge for an infinitely long time
b) Allow the charge voltage to go ABOVE 4.20V and terminate charge at a given current so that the cell resting voltage drops down to 4.20V
Charge voltage yes - not necessarily battery voltage
The basic idea is that you don't want the cell to exceed 4.20V at ANY time. Charge load voltage is VERY relevant. Why else does the CV phase exist? the CV phase is to prevent rises in voltage over the recommended 4.20V during charge. If you allowed the cell to charge like a NiMH, with full rate all the way, you will have a charge load voltage of 4.4V, which once removed, will have the cell drop back down to 4.20V at rest. Your argument in red accepts that charge voltage goes over, but battery voltage is the only relevant one. Cell voltage at any time at any state is important.
End of the day, Whats more important is the degree that you exceed by. 4.22 isn't going to cause explosions like 4.40 will, but its cumulative cell damage that were more concerned about. I could set my iCharger to charge to 4.22V with a high cutoff current, and it too would give me the same 4.20 resting voltage.
If the budget charger doesn't charge for infinity time, and has a high cutoff, and also achieves 4.20V, then it too must be charging slightly higher.


The number one rule of a True CC/CV charger is that it Never exceeds 4.20V, and because it usually terminates at a current above 0mA, (usually 1/10 charge rate), it CANNOT EVER give you a resting voltage of 4.20V.

So how does our budget a charger achieve a resting voltage of 4.20V??? Simple - It either charges for infinite amount of time, or it has allowed the cell voltage to exceed 4.20V
(remember, our cell protection circuits protect for over-voltage between 4.25 to 4.35V. It can stop huge over charging due to wrong chargers etc.. but it won't stop regular insidious overcharging with less accurately regulated chargers)

2) CC/CV charging profiles are the Ideal charging profile for lithium. Lithium cells that we commonly use, charge to a fully charged voltage of 4.20V. A cell at this voltage is safe, and this voltage Must not be exceeded at any time.

The CC part is where a cell can be charged at its recommended charging current, without exceeding the max charge current. In this part of the cycle, the voltage rises. Until which time it reaches 4.20V per cell, then the charger will reduce current to the cell to maintain 4.20V. This is all governed by the internal resistance of the battery.

*A budget charger doesn't have a true CC/CV profile, it only roughly emulates it, reducing current much earlier than necessary before the cell has even reached 4.20V. This is effectively means during the time in which a charger Can be very safely delivering charge power, the budget charger is already backing off. This period is also where charging time could be significantly reduced. So it is less stressful , and gentler on the battery ...
Agreed, a lower charge current will be gentler on the battery, but you can ALSO set the hobby charger to a lower charge current. Then you could say that while the budget charger averages a "CC" phase of 500mA, with an initial 1A, the hobby charger held 500mA all the way in CC, and never gave 1A initially, and call at as being far better on the cell!
I think we both agree on the idea that higher currents --> more damage. And we both agree that with a hobby charger comes the need for the user to be aware of what their doing, and set charging currents accordingly.

At the last part of charging, the CV phase, where the overcharging is done, the budget charger keeps going and as demonstrated above, Must be allowing a slight over-charge to achieve a 4.20V resting voltage.



So what does the budget charger give us? A Slower charge because its backing off too early, but an over-charged cell because its not truly regulating to a maximum 4.20V.

A resting voltage of 4.17 is therefor MUCH healthier than a resting voltage of 4.20V.

Lets have another example,
It is true that this voltage differential (and voltage settling) will occur with hobby chargers, simply because they usually terminate charge at 1/10 charge rate. A 0.5A charge will terminate at 50mA, and accordingly with a internal resistance of 500mOhms, this equates to a voltage increase of 0.02V.Therefore a charge that terminates at 4.20V, 0.05mA, will give a resting voltage of 4.18V.= The issue was , folks buy hobby chargers to be safer , and to charge cells so as not to damage them , and then turn around and charge @ higher current rates that [ my opinion ] stress the batteries more than the cheap chargers they are avoiding , and at the worst time , closer to completion . [ This is up to the individual ]
And if you charge at a lower rate , then is it faster or better ? Me thinks not . [ Thats me ]
If your budget charger that terminates at 50mA, gives a resting voltage of 4.20V, it must have terminated at 4.22V. = Well the charger voltage may be 4.22 , this does not mean that the battery voltage is the same , as these chargers usually run 2 tenths above batt voltage . So if it terminates at 4.22 , then the actual charger voltage would have been more like 4.24 4.25v
What are you saying here? I'm not sure where we are defining the measurement of voltage here. I have always been talking about voltage at the Cell only.
Reality here is that we need to be talking about the voltage of the CELL ignoring all cables/connectors and such. Wires have a resistance, and under load the voltage measured at the PCB and the cell itself will be different. HKJ has gone to much effort to ensure that the voltages he measures in the chargers represent cell voltages, rather than measured voltages at the charger, etc... I know my iCharger outputs 4.35V at the PCB, but has External separate measuring wires that carry no current to accurately measure Cell voltage, and can apply a higher voltage to compensate for the voltage drop of undersized charging wires when I'm charging my cells at 5A, achieving 4.20v at the cells.
On the other hand, if your talking about cell resting voltages, vs charge load voltages (at the cell), again, this was discussed above.
Will get to this as time permits :

If your budget charger that terminates at 50mA, gives a resting voltage of 4.20V, it must have terminated at 4.22V. Lets start here ....

First , 4.22v is nothing , insignificant voltage to worry about , and is often touted as something for people to worry about . [ Why do people bring this up ? I dont know ]

Sort of agree here, 4.22 v isn't a huge amount to be worried about in the short term.

If its something about stressing older cells , ?? . Most of the chargers I have are sensitive to the internal resistance of the battery , so when nearing completion , a cell with higher internal resistance will terminate at a lower voltage , (yes, because the cells have a high floating voltage due to the internal resistance, and because the measuring time is no longer than a fraction of a second, the cell voltage is not allowed to "normalise" which you also said earlier could take up to half an hour. It is reasonable to say that high internal resistance cells here do terminate early due to the higher charge load cell voltage.

[ Tr003 , WF-139 , WF-188 , Xtar to name a few ] and there are some charger that will try very hard to bring the battery to 4.2v such as the Soshine and TR-001 , but this is and will be about buyers knowing or educating themselves . Because these cells don't over-charge past 4.20V as much as the other chargers.

So rather than trying to scare people , we should be trying to educate them .

Also dont forget , @ 50mA , its a very gentle charge rate , gentle = low stress , and yes it takes a while .

Absolutely, 50mA is pretty low already, and at this rate as calculated before, with a 500mOhm cell, will only give a 0.02V difference between charge load, and resting voltage. Higher current cells with 50mOhm internal resistance will by now only have a 0.002v difference, effectively "maintaining" 4.20V due to measurement accuracy

[ Im out of time this morning - so maybe 8 hours from now ]

Cheap charger behavior , now most cheap chargers do the pulse charge method ..

What that is it , charges , stops charging to check the battery then continues to charge .

Now when it stops to check the batt , the charger than is able to adjust voltage [ of the charger and charge current ] ..

Now while the charger does indeed have a higher charge voltage [ lets say 4.22v near termination ] it does not mean that this is the voltage of the battery [ one needs to understand this ], and because it stops and starts , when the battery reaches 4.2v , it should [ should ] stop charging .

here your saying that the battery voltage under charge is 4.22V. This is what I've been saying.

Now as to the termination voltage of the battery , two factors are involved , the charger [ obviously ] as well the battery ..

Depending on the internal resistance , and the sensitivity of the charger to such , can have a contributing effect on termination voltage ..

A battery in rerally good condition may terminate 4.22v or 4.21v and hold said voltage .. Because its a good quality battery ..

A battery in not so good shape may terminate 4.17v in the very same charger , and a cell on its last legs could very well go 4.2v ...and hold the voltage .


Its important to understand there are so many variables involved .

As stated earlier, internal resistance of battery -> high floating voltage under charge load + short measuring time not allowing voltage to settle --> cuts off before energy has actually been put into cell, therefore once "terminated", the cell hasn't actually taken on charge, and the resting voltage is lower

But yes, absolutely, there are many variables involved here.

I think we both agree on the idea that higher currents --> more damage.

And we both agree that with a hobby charger comes the need for the user to be aware of what their doing, and set charging currents accordingly.

If no one wants to read above, this is my summary, I think i finally understand where the problem was. (a difference in definitions)

1) My only problem with your OP is the way you used the concept of cell resting voltage to argue that the true CC/CV charging of hobby chargers is not as good for cells, however there is no relationship between these under the criteria of the standard charging protocols offered with the chargers in question.

2) Also, the comparison is wrong because of your difference in the definition in what cell charge voltage vs cell resting voltage should be, and the way each charger uses each in relation to the understanding of how hobby chargers use this voltage, vs how budget chargers reference 4.20V according to the way you described it.

What I'm now understanding, is that you see cell charging voltage (at 4.22) as irrelevant, and that the resulting cell resting voltage of 4.20V is good (at 50mA termination). Because the budget chargers measures resting voltage in the "off" time.

We must remember that the hobby charger will charge to a max cell charging voltage of 4.20v, and will accordingly have a resting voltage of 4.18. (at the same 50mA)

SOOOOO - This is the 0.02v discrepancy that you are describing, due to the difference in the way each charger defines how it wants to use termination voltage. NOT how it was charging the cell in the CC phase.

30

Now was that a long post or what... Sorry guys.

Meant to be studying for exams... mmm so what kind of antibiotic should be prescribed prophylactically in the event that a patient has had a history of rheumatic fever, amoxicillin 2g, 1 hour before treatment such as periodontal debridement?

31

Some charger data:

WF-188, charges with 300-350 mA until the cell has reached 4.2 volt without current, the actual voltage on the cell can easily be 4.25 volt.

WF-139, charges with 350 mA but does sometimes reduce the charge rate, I have seen up to 4.35 volt on the cell.

Both charges will stop when the cell measures 4.2 volt without current. I.e. when the cell is removed it will not read more than 4.2 volt on a DMM (there are some tolereances).

A hobby charger charging with 1A will only have 100 mA current when it terminates the charge at 4.2 volt and will not go above 4.2 volt.

32

Darn cant reply , page wont show .. Must get back to school work

1) My only problem with your OP is the way you used the concept of cell resting voltage to argue that the true CC/CV charging of hobby chargers is not as good for cells, however there is no relationship between these under the criteria of the standard charging protocols offered with the chargers in question.

Now I have a problem with this , I dont remember saying any such thing ..

So if your going to make stuff up , how can I reply or argue against some thing I didnt say ?

I think this discussion has de railed , because your talking about things I havent said or intended ?

Why would you do that ?

33

I certainly remember reading it just as quoted, I thought it quite strange at the time, the OP has obviously been edited.

The OP certainly seems to abound with misunderstandings and lack of real hard facts.

34

??????????????? WTF - Are you guys trolling ... hmmm

35

The op was edited just as I made a basic posted and has been edited many times since, a cheap basic charger with no cc/cv can not be better then a good hobby charger with cc/cv since Li-on,s are ment to be charged with it, also a cheap charger that will only charge at 1 amp is not good for all batteries, this has been an interesting thread

36

My intention is talk about the error in your argument, and to correct this for the benefit of everyone, there is nothing against you. Your one of the highly valued members of this forum, and its great having you around. I'm not going out on a limb to try to make stuff up, its not what I'm trying to achieve at all.

My only concerns are just in the theory side of things

1) The argument was based on a "proof" that is not causally linked to the main argument.

2) The small print - the inconsistencies in the definition of your "proof" (voltage at cutoff), which once corrected, render your "proof" invalid.

Do you agree with the following quotes, I am trying not to take them out of context, but my understanding is this is your take on the topic.

The Point that is being made:

It was stated that charging cells at a higher current, for longer can cause more stress for the battery

I definitely agree here, charging at a higher average rate results in more cumulative damage, This is fine by me. Its the way you prove this that is what I'm on about.

The Proof that was used:

That a cell off a hobby charger will sag to 4.15v while a cell off a budget charger will rest at 4.20v

The Problem:

1) Using cell resting voltage to prove battery cell stress when both chargers terminate at the same current threshold. In a CC/CV charger with the same termination current, charge current in the CC phase has NO relationship to the voltage of the cell after the CV phase. (within normal charging circumstances)

2) Definition of "termination voltage" -

You have stated here that your hobby charger charges to 4.2v.

You also stated that the cheap charger will Terminate at 4.2v

This may sound the same, but its in the details of what you mean by each.


With the cheaper charger, you define the "4.2v termination" as one where the resting voltage is 4.20v, but the cell charge voltage CAN be above by 0.02v. 4.22 for example.

On the other hand, The hobby charger we know when we set to charge to 4.20v, will never exceed a cell charge voltage of 4.20v. As you indicated, the charge voltage can be 2 tenths above the battery voltage, so the battery voltage must be 4.18.

We need to be comparing apples to apples! The following are the True Cell Charge voltages at termination based on the information provided.


Hobby charger - Cell Charge voltage of 4.20V

Cheaper charger - Cell Charge voltage of 4.22-4.23V

And given that we expect a 0.02v drop following removal of a 50mA charge current on a cell with 500mOhm internal resistance, we can expect that the cells with have the following resting voltage

Hobby charger -> 4.20 - 0.02 = 4.18v

Cheaper charger -> 4.22 - 0.02 = 4.20v

What I'm trying to say is, the difference is actually just a result of having a different charge voltages at termination, and cannot be used as proof of cell loading because both chargers taper off to the same termination current

37

The OP still carries its main idea. I wouldn't go accusing anyone yet.

Im after an educated and conducted discussion here about the definition of charge termination and how this has may have been accidentally used as an proof that one charger is not as good as another. I would love to get some feedback from other members who are comfortable to discuss this topic to chip in.

Maybe I'm wrong, but I'm currently 99.9% sure that this has just been an oversight in the way charge termination has been understood in the OP

38

Original Post changed How ?

If mem serves additions were made , but nothing was changed or removed ..

In an attempt to improve explanation .

Which has obviously failed .

What part of [ Im talking about charge current ] dont folks understand ? Im not faulting the Hobby charger , only the way its used .

And questioning how much better can it possibly be ? Than the humble cheap charger ...

I almost feel like ive stepped on the toes of Surefire fans .

And I have never mentioned CC/CV or how I feel about it , merely questioned whether CC/CV being best is opinion or fact [ established rather than opinionated to such status , and in a later post ]

So if we cant stick to what was said in the OP .

Obviously things have been taken out of context and assumptions made , and I have failed in creating a clear and precise explanation free from interpretation by the reader , my bad .

Hmmm ...

How to explain things so they cant be interpreted in any shape or form ...

18650 - Only talking about charging the 18650 , not other battery is being considered , in any shape or form , to interpret so is to be in error !

Cheap nasty charger = Soshine SC-S2 , this will be our cheap example as it starts charging around 1A

By the time you get to 3.8v [ batt voltage ] it has slowed to 900mAh or so

and by the time you get to 4.05v [ batt V ] it has slowed to 400mAh

and 200mAh @ 4.15v

@ 4.18v [batt V ] it has slowed to 40mA

@ 4.19v [batt V ] it has slowed to 29mA

@ 4.2v [batt V ] it has slowed to 25mA

This charger does not terminate charging but simply continues to lower the charge current

@4.23v [ batt V ] it is charging at 4mA

The Soshine is a notorious over charger if you dont pull the cells on the green light , and I would not recommend this charger to inexperienced users

It does how ever give the green light when the battery is 4.2v , and it does push cells to 4.2v , and if you want to get your cells to 4.2v , then the Soshine is the tool for the job .

[ Another charger to use to get cells up to 4.2v = Trustfire TR-001 ] for reference only - will not be talking about this charger !

Ok so we have our cheap charger ....

Now lets talk batteries :

As examples , I will be talking about top shelf batteries , Samsung - Panasonic - Sanyo

Its important to understand batteries , and that no matter what brand you buy , there will be variation , even if they came from the same production run , though it would be nice to think that they would be closely matched , for capacity and discharge capability , but never count on this as a rule .

These are unprotected cells , and as soon as you add something to the equation , you add another variable . [ in this case the protection circuit ] Another important part is the quality of the cell , and as before , there will be variation from one cell to another even in the same production run .

Now in a quality laptop battery pack , which most likely has balance charging , and the manufacturer may or may not have matched the cells [ probably not ] , but would have passed some sort of quality test , and may or may not have been graded according to quality or test results ...

Now this brings to question ? What cells are we getting ? Top shelf laptop cells , or ???? anyhow , getting of the track here ...

Lets talk discharge for a moment , [ Sanyo 2600 ] I have two purchased about 6 months apart .. One discharged @ 3.5A and the other 3.6A , that is very close performance in the same light for 2 batteries purchased from two different vendors at two different times .. [ Just an example of Sanyo 2600 ]

Also the Sanyo 2600 is my second best highest discharge capable battery [ New Panasonic 2250 from Carllie's is my best ] as well as the Samsung 30A [ 4.35v ]

Anyhow , quality cells behave a little different to the cheaper variety . [ This is important to understand ]

Everyone wants value for money , which is quite understandable , I feel the same way .

My only issue with some batteries is that while they may test well to begin with , they may not last the distance .

And more user input is required here ...

Ok the point , there are some really good batteries out there .

Battery charger relationship :

The battery is designed to store energy , discharge energy , and have the energy it stores replaced [ re-charged ]

The slower you charge a battery , the more current/energy it can store

As mentioned , the faster [ higher current ] the battery is charged at , the greater the resistance to being charged ..

More current also = more heat , so energy that was going into the battery , is meeting enough resistance to generate heat , this heat = lost energy and can also be expressed as stress [ at least I will ] , and by stress I mean the battery is resisting being charged ..

So the higher the charge rate , the greater the Resistance = greater stress [ I have explained this well enough ? ]

Now whether you use the battery or not , the Li-ion degrades [ new tech may improve this ] , but ATM , ....

Now this is very dependent on the quality of the cell in the first place , and I dont think you can put a hard or fast figure on this ....

Ok , now to the point I was trying to make ...

I see people using Hobby Chargers to charge there 18650's at around 0.8A to 1A , and do so because the Hobby Charger is safer [ Which it may very well be ] , and they think they are being gentle on the battery ... [ Now my issue here is Charge Current ] shall I repeat my issue ?

Now I see a lot of folks who who are following this lead [ buying hobby chargers to charge 18650 cells ] and using high current [ around 1A ] and then wondering why the battery sags to 4.15v or lower ... [ Some folks have blamed the battery for the sag ] And experienced people who should know better , have then also backed up the battery theory ...

Yes Im departing from the OP a little , but I dont want to leave room for interpretation .

Now it is true !!!!! That cheaper batteries will most likely [ Those variables again ] have more internal resistance and there for sag more , but when someone is using a new quality cell , this becomes less likely [ those variables again ] but not 100% without further testing to verify [ that it is indeed a bad cell , which is why direct comparison becomes important to establish a base line ]

Adding = Blaming the battery , when they should consider there charge rate !

Now to my comparing a Hobby Charger @ 1A and a cheap Charger [ In this case , the Soshine mentioned earlier ] Sorry This statement may confuse and agitate

I should have been even more clear = They start charging at 1A - Charge algorithms or charger behavior will be as per factory product [ I have quoted Soshine behavior , not Hobby Charger , as I dont use such for charging ]

Im in no way questioning the CC/CV of the hobby charger [ was I clear on that ] but the charge current . [ used by folks - and chosen by them of there free will ]

So the higher the charge current = the greater the resistance = more stress on battery = takes longer to normalize [ reach stable voltage that will be retained for some time - not taking self discharge into account ]

Now when charging at [ lets call it @ 1A ] with the hobby charger , the charger completes the charge cycle before the battery has had a chance to normalize , the higher the current , the longer it takes [ to normalize ] = the greater the sag after charge ? [ was that clear ]

/\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ /\ ....... Edited [ obviously not clear ] I dont know how better to explain it ?

Now Comparing to the Cheap charger [ Soshine mentioned earlier ] , even though it starts charging at 1A , it begins to tapper off the charge current long before 4.2v [ is this clear ]

Thus allowing the battery time to begin to normalize whilst being charged [ is this clear ]

and by the time it approaches 4.2v , the battery has had time to normalize [ there is less internal resistance , less heat , less stress ]

And the lower the terminating current [ near completion ] , the less stress on the battery [ when it will have the most resistance to charging ]

Now I havent talked about CC/CV [ hobby charger ] or the Cheap chargers charge method etc ! [ are we clear on that ? ] + Edit = [ Pulse Charge ]

And Im not taking time into consideration either , the Soshine is touted as a fast charger , but it really isn't , because of the low terminating current , its not fast at all

Now what I will touch on ....

Battery termination .... [ what ever charger ]

[ still talking about charge current , that hasn't changed , so dont read more than Im writing ]

Higher charge current = higher battery voltage [ under load of being charged ] it takes time for this to lower [ its not instant ] and I have noted up to 1 hour for this ..

So as the charger reaches 4.2v , and terminates the charge , the battery under greater load will sag more than the battery under less load [ internal resistance ] as well the battery under less load will have a voltage closer to normal [ resting voltage ]

So if the battery is trickle charged to 4.2v at 25mA , it is more likely to hold voltage on completion [ can you understand this ]

I really didnt think any of this was rocket science . And I hope I have explained my thoughts more clearly ...

This has been about Charge Current , and nothing else , if you have read more into it , I just dont know how better to explain .

really old and tired old4570

Edit = Ooops , and when I say EDIT - I mean I have added , not changed or taken away ....

EDIT = obviously failed again