Thanks for the info!
To test your hobby charger !
Verify battery voltage first , let it rest for a while [ like 24 hours ] , then verify with MM ..
Now place in Hobby charger , what ever function you chose , it should test battery state [ voltage ] first and give a read out , before continuing with the function .
If the read out = MM then its calibrated correctly , if not , say its a little out , then you should be able to adjust the calibration [ iMax B6 can be adjusted ]
Unfortunately one cant program the charge cycle behavior . [ B6 ]
hey old is the imax b6 still a one shot deal with calibration
If mem serves , its a one shot thing for balance charging , for voltage calibration , as many times as it takes ...
I haven't fully read the following posts, but I Disagree with the OP on several points
- How Resting Voltage works, vs the way a cell is treated
- The overall concept of why true (CC/CV) vs emulated CC/CV is better
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.
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,
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.
Very informative and useful , okwchin . Thanks .
No time for a complete reply ,,, [ school ]
But several miss quotes , and errors to reply to as time permits ..
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.
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 !
- How Resting Voltage works, vs the way a cell is treated
- The overall concept of why true (CC/CV) vs emulated CC/CV is better Is this gospel ? or merely the most accepted ?
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.
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. 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,
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 .
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
Having a bad day ?
Banter is good , when people take pot shots , gives you a chance to plug the holes !
Hehe, more fun!
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.
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.
- How Resting Voltage works, vs the way a cell is treated
- 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.
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.
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. So it is less stressful , and gentler on the battery ...
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,
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.
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?
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.
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 ?
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.
??????????????? WTF - Are you guys trolling ... hmmm
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
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 ?
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 hobby charger maintains its charge rate longer , there by charging faster ,
But with the Hobby charger , it will stress the battery more , how do we know , because it [the resting voltage] sags !
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
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
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
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 ?
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" -
But with the Hobby charger , it will stress the battery more , how do we know , because it sags !
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 ?
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.
(okwchin)If your budget charger that terminates at 50mA, gives a resting voltage of 4.20V, it must have terminated at 4.22V.
(old4570) 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
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