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

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old4570
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Hobby Charger VS Cheap Chinese Charger [ charger behavior ] some thoughts

From time to time I see folks complaining/questioning there battery resting voltage after charging there 18650 with a hobby charger .

A lot of people simply cant understand why there battery wont hold 4.2v after charging . 

So I will attempt to enlighten :  

Have you noticed voltage sag when turning on a device and monitoring voltage ?   Lets talk AA for a moment , and say you have a 1.75v Lithium cell , in your flashlight @ 2A current draw that battery can sag , bellow 1.4v under enough load ..

Now the same goes for Li-ion under load , a good quality cell , @ lets call it 1A discharge , may sag to 4v or even lower , cheap nasty cells  I have seen sag all the way down to 3.5v under 1A load .

The same thing happens when charging , but in reverse , rather than dropping voltage , it is increased under the load of having current pushed into it .

Remember , batteries are designed so that energy flows out , not in , so energy needs to be forced in , this creates a resistance load from the battery that needs to be overcome by the charger , usually in the form of increased voltage [ with me so far ? ] 

Now a lot of folks using hobby chargers run higher charge currents than say the usual Chinese charger [ lets call it the much loved WF-139 ] . 

So what folks need to understand is that it takes time for a battery to normalize after and during charging , and that Hobby chargers @ higher current dont give the battery the time or opportunity to normalize during the charge cycle .[ So many charge 0.8A to 1A , so lets call this the Charge rate for the Hobby Charger ] 

So once completed , it may take an hour for the battery to normalize its resting voltage , which due to the Hobby charger behavior , may be quite a bit less than many expect .

 

What is the issue ?  The hobby charger maintains its charge rate longer , there by charging faster , and also not allowing the battery to normalize during charging .

This is where the Cheap Chinese chargers excel :

All the chargers I have , tapper the charge current , so even if the charger were to start @ 1A charge rate , it begins to tapper the charge rate giving the battery time to normalize under charge , and its charging at a higher rate at a time when the battery is more accepting [ empty ] of higher charge rates ..

The Cheap charger may have tapered down to  300mA by the time you get to 4v on the battery voltage , 200ma by 4.1v and by the time you approach 4.2v it may be doing 60mA and have a terminating charge rate of 40mA [ most chargers are less than this - but Im going with highest one I have as an example = charge cycle current ] 

Anyhow , what this means is , the Cheap charger [ Compared to hobby chargers ] does a really good job of charging the battery , and in the real world [ rather than some ones imagination ] , may actually stress the battery less , than the hobby charger . 

And lets not forget , if you have good quality batteries , they wont mind being charged to 4.2v . Whether you charge to 4.15v or 4.2v , the better the battery , the less it will matter , as the batteries are under the greatest load / stress near completion ..  And if you complete the charge gently [ Cheap Charger ] , then how much difference will 0.05v make ?

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 dont need to be a rocket scientist , to understand that , these cheap chargers are maybe not so bad as some would have you believe ...

Now if you have a $200 Hobby charger that can be fully programmed for the charge rate , that's fine , in fact its fantastic , but when a $8 Chinese Charger from HK can do the same thing , and save you $192 , then I cant knock or put down the cheaper product that does the job . 

Life is , to each there own , but the king is , knowledge !  [ I dont know everything , but hopefully I have shared some of the little I know ] 

This is a very light weight explanation  ..

And hopefully , explains that , Hobby Chargers are maybe not the best option for the 18650 , possibly if you insist on using one , you may reconsider the reasons for such , and maybe its time to lower the charge rate if you suffer from a lot of voltage sag on completion , and maybe you stressing the battery more than you thought [ lots of sag ] 

The battery is under the greatest stress near or at completion , and this is where you need to be gentle 

And empty battery is more accepting of higher charge rates , than one that is not empty 

Hobby chargers are wonderful things , but like any tool , when misused or misunderstood 

Are cheap chargers so bad [ if you have a good one ] as some would have you believe , or is it simply a - Mine cost more than yours thing ? [ so it must be better ] 

Price makes right !  

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

Edited by: old4570 on 10/25/2011 - 22:34
scheven_architect
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Interesting! TY very much!

 

 
gcbryan
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Thanks for the explanation. All I have is a cheap charger and Trustfire batteries for that matter (and Eneloops of course). They all work fine.

I think much of the appeal of the hobby charger is that it's expensive and must be better and it has read outs and more controls. I don't want playing with batteries to be a full time endeavor so unless the cheaper versions (charger and battery) start to not work out for me I see no need to get anything else.

benckie
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very good post old.

i think some people think the higher the charge rate the better, yes it will be faster but all in all the battery will sag and it will hold less mAh in the end, not to mention it will raise the internal resistance of the battery and shorten its life.

the issue i think is not the hobby charger holding the charge rate longer or stressing out the battery, its people over charging the batteries take an 18650 since the charger will cut out at 4.2v or what you have set it to if you push to much current into the batteries they will rise in voltage hit the 4.2v cut off early and cut off they will not have time to absorb all the mAh and then once the cell is rested and the voltage is check it will be lower then 4.2volt  and the battery will not give its full run time once used cause it didn't get to take its full mAh and its full voltage and I'm hopping we all understand the more mAh the longer the torch will run before needing a recharge, this also works for all rechargeable batteries.

there is other factors in this the charge mode used on the charger for example a fast charge will only charge to 80 to 90% the batteries will also make a difference the cheaper the battery will impact discharge and charge rates, a cheap hobby charger will also make a difference and because hobby charger,s let us humans do the thinking and we are an impatient breed we tent to over charge then ask why the rested voltage is different

I'm into remote control (RC) as a hobby have been for 20 years or so i have always had hobby chargers over the years and i run a middle of the road hobby chargers for my RC and my 18650,s i find it is more precise then the cheaper stuff but there need,s to be some understanding and knowledge, i could not go back to plug and play chargers as i would need so many.

while I'm new to 18650 batteries I'm not new to li-xx batteries i use slow charge,s and i always balance charge my 18650,s its slower, the charge rate ramps down giving the batteries time to normalize and this is where they will take a bulk of the mAh back.

i charge my 18650,s at a max charge rate of 0.5 amps (500 mAh) and i only use cheap batteries the trustfire flames, this is about the Maxim i believe these batteries can be pushed over a slow balance charge to take the Maxim mAH , this works out at around 0.4C for the charge rate, i believe 0.2C is better but then i pick the higher charge rate (C) to save time.

with my hobby li-po batteries there normally is a 1C charge rate so 1 x capacity of the battery divided by 1000, so if you have a 2200 mAh battery its 2.2 amps most li-po,s  can be charged at 2C + so 2 x capacity, i mention this so people might understand the above when i say 0.4 and 0.2C.

over the years Ive found most cheaper chargers will do the job and some do it well, i would not recommend people who are not into RC to spend big $$$ on chargers and power supply,s as there is no need a couple of cheaper chargers like the WF-139 or the WF-188 would be fine if they don't over charge if they under charge no problem but most batteries are protected.

but also over the years i have noticed a lot of the cheaper chargers not to be 100% accurate or calibrated to there full potential and have noticed differences of .01 to 0.4 volt + some under charge some over charge and there is a difference between each charger i guess this comes down to quality control and some times you get what you pay for but we all want to save money.

i cant say a WF-139 is better then a $200 hobby charger that's full programmable, with calibration features that's accurate with in 10 mv (0.01v) or as accurate as your fluke DMM,s as i personally don't think it is, but like i said i cant recommend torch addicts to spend that money on what i call a half decent charger and power supply set up just for torch batteries, i also cant recommend the cheap imax b6 balance chargers due to there inaccuracy and there poor performance with accuracy and nimh charging.

like you say knowledge is the king, there needs to be some understanding and often to save time charging will shorten the life of your batteries and they will have slower resting voltage, its a give and take to me, the user needs to find the middle ground between Maxim mAh good rested voltage and charge time, one thing i will say that's good about the hobby chargers is understanding as you see whats going on and after a while to will make sense to most people.

with hobby chargers on the display screen you can actually see what your charging and discharging habits are doing to your batteries, you will see voltage sag with high discharge rates and you will see the voltage rise with high charge rates but once the battery has normalized or rested it will show other wise so then you know your over charging.

E.g when charging a 18650 at 1 amp say is you start the charge at 3.2 volt you will see the battery voltage climb up as soon and the charger kicks in but if you stop the charger you will see the battery voltage fall back to where you started, the same goes for discharging your 18650,s (but back to front) if you discharge a 18650 at 2 amps with the batteries resting voltage of 4.18v and you set the charger to shut down when the discharge hits 3v you will notice the charger will shut off when the battery hits 3v under load but once the load is taken off the battery will climb back up the battery has not had the time to take in or out its mAh.

this is why slower charge and discharge rates are better as the batteries will be closer to true rested voltage and mAh or normalized like you say, now like we said knowledge is power, but with the WF-139 you can not see this happening in front of your eye,s on the screen and a lot of people most likely will not research this and if they don't have a back ground in electric,s or RC so they might be surprised if they get one it will genrate questions.

also some hobby chargers are good for knowing how much mAh is going into the battery so you know truly how the battery performs plus features like data logging internal resistance testing comes in handy and can help you pick and chose what batteries to use say for direct drive torch,s and watching a good hobby charger in action will help people understand voltage drop and sag and voltage rise when charging over time.

Ive read on here in the past and even today plus of other forums in the past of these cheap chargers not shutting off and over charging and so on, but in other peoples eye,s they are the bee,s knee,s, i believe my $200 hobby charger and power supply is better then a WF-139 or an imax b6 not because it cost more and makes me better then every one else, its better cause its programmable it has more features i can charge multiple li-po,s at 10 amps for my remote control cars i can charge my xbox 360 controller batteries my camera batteries my torch batteries my radio batteries my 9v nimh,s its more accurate and it will work in the car on 12volt and it works at home i even take it on holidays to charge camera batteries it is used attest every couple of days and has payed for its self already.

i can easily see people with out a RC or electrical knowledge not understanding loaded and unloaded voltage and not understanding rested cell voltage and they would be seeing data they are not used to yet, if any one with a hobby charger is questioning the rested voltage of there batteries then they are over charging the batteries most likely.

instead of charging one battery at 1 amp with a hobby charger your much better off charging 2 to 6 or more at 0.5 amp the batteries will charge better hold more mAh giving them more run time and longer shelf life and because you are charging multiple batteries it works out much quicker then trying to force feed one and there will be less or no rested voltage difference because its being charged at a lower charge rate but your still saving time as your charging mutable batteries.

i like you believe knowledge is power but i don't believe its the hobby chargers fault i believe its user error mostly wrong charging modes cheap batteries and over charging a good hobby charger used correctly with a half decent battery will not stress out a battery or let the battery sag to 4.15v after its rested

joerch
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My hobbychargers (Graupner, Robbe) decrease the current when hitting the 4,2V mark and push the last 5% of energy very slow with still decreasing current into the battery. I get them with perfekt 4,20V from the charger and they hold this voltage. Checking about a week later it is of course a bit lower at about 4,17V or so, nothing to worry about.

The charging method is called CC-CV, constant current-constant voltage.

 

old4570
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I agree , chargers are tools and as such need to be used correctly .. 

Unfortunately - while many express the virtue of hobby chargers , they seem to ignore the pitfalls , and give bad advise on there use . 

I honestly dont understand how people can knock the 18650 chargers [ Trustfire TR-001 etc ] since the majority do a great job . 

But then there are some seriously good hobby chargers out there if you want to pay the price ...  

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

HKJ
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joerch wrote:
The charging method is called CC-CV, constant current-constant voltage.

 

That is the methode the LiIon cell manufacturers recommend.

A typical charge specification has a maximum voltage (4.2 volt) and maximum charge current (Like 0.5C) and a minimum charge / cutoff current (like 80 mA). The hobby charger follows this, except the cutoff current is usual defined as charge current/10. I.e. when charging with 1 A, the cutoff current will be 0.1 A.

This charge methode will not force a high voltage on an old cell (This is damaging to the cell), but will stop charging when the cell cannot accept more current (Defined with the cutoff current).

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

old4570
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HKJ wrote:

joerch wrote:
The charging method is called CC-CV, constant current-constant voltage.

 

That is the methode the LiIon cell manufacturers recommend.

A typical charge specification has a maximum voltage (4.2 volt) and maximum charge current (Like 0.5C) and a minimum charge / cutoff current (like 80 mA). The hobby charger follows this, except the cutoff current is usual defined as charge current/10. I.e. when charging with 1 A, the cutoff current will be 0.1 A.

This charge methode will not force a high voltage on an old cell (This is damaging to the cell), but will stop charging when the cell cannot accept more current (Defined with the cutoff current).

And many dedicated 18650 chargers do exactly the same thing ... [ Sensitive to the internal resistance of batteries - therefore terminating early ] 

And yes there are some chargers that force batteries to a higher voltage state , but depending on the school of thought ? 

There are those who believe in conditioning batteries , even Li-ion ..

And some Li-ion get better after some use ?  If you cant condition Li-ion, this should not happen  .

Can you bring back degraded cells ?  

One of these days , Im going to look into it , probably when school finishes , I will run some experiments , to see , condition new cells , or recondition old cells in any shape or form 

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

MixoMaxo
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Imho chinese cheap chargers are great if you use protected litio battery, because the only cons is that them usually over-volt or can broke keep charging and making burn/explode the battery(very remote case).

Litio are very solid but can be dangerous, on the other hand for nimh you need more care and a good smart charger to keep them healthy.

ChibiM
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Can somebody also tell me how to recognize bad cells, by looking at there resting voltage?

I have some batteries, from a dead laptop....(not dead batterypack!) and would like to know if they are usable or not..
my TR001 only charged them up to 4.16-4.17V. (i dont know if my DMM is correct either)

If someone can give a link, then people dont have to explain it twice..

thanks

robertkoa
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 I noticed that my cheap charger charges at or outputs 600ma.

 

IF I get a charger that outputs 1 Amp- will this charge the batteries more quickly, and if so will it be 30 to 40% quicker?

 

Noticed an Ultrafire cheap dual charger that indicates 1 Amp.

HKJ
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robertkoa wrote:

 I noticed that my cheap charger charges at or outputs 600ma.

IF I get a charger that outputs 1 Amp- will this charge the batteries more quickly, and if so will it be 30 to 40% quicker?

 

High charger current will charge faster, but there are a couple of not as much faster as the current is higher.

With a CC/CV charger the charge phase is in two parts, first a CC (constant current), this part will be considerable faster. If you double the current, this phase will take less than half time.

The you have the CV (constant voltage), this is longer at higher charge current (because you reach the CV phase faster). How long it takes is also very much depend on the cutoff current, i.e. a charger that stops at 300mA will have a shorter CV phase, than one that stops at 100mA.

 

The above is only valid for chargers following a CC/CV charger curve, but very few chargers does that and on many cheap chargers you can not thrust the specified current either. You best bet is to find some reviews that uses comparable cells and see the actual charge time measured.

You could use the charger reviews on my website for that Wink, the AW18650-22 cell I use has nearly the same capacity in all my measurements (albeit a low capacity).

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

old4570
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Its very hard to determine that ..  [ Cell condition ] 

There are signs to watch for . but after charging and then discharging a bunch of 16340 ...

What to watch for = 

Wont hold a charge , voltage drops faster than other batteries [ still not a sure sign ] 

Sag after charging [ again not in any way 100% ] 

To really sort out the crap from the crop so to speak , you need to discharge the cell , this is the only true way to tell ..

 

An example ..

I had a 16340 that charged to 4.2v and held it , voltage sagged very slowly over time [ as it should ] 

There were no real warning signs that the cell had degraded , until discharged and the cell returned less than 200mAh capacity . 

Originally it was maybe 530mAh , but after some 2 + years of light use , had degraded to under 200mAh 

So if your hanging onto your batteries or trying to reclaim older batteries [ from laptops ] a hobby charger might be a invaluable tool to really know whats going on . [ running discharges ]

You dont need the most expensive , you just need one thats going to tell you what you need to know .  

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

benckie
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ChibiM wrote:

Can somebody also tell me how to recognize bad cells, by looking at there resting voltage?

I have some batteries, from a dead laptop....(not dead batterypack!) and would like to know if they are usable or not..
my TR001 only charged them up to 4.16-4.17V. (i dont know if my DMM is correct either)

If someone can give a link, then people dont have to explain it twice..

thanks

 

resting voltage will not always tell if you have a bad cell, discharging will, you can put them in a torch and gun them on high for a while then use a DMM but the best way would be to cycle them on a hobby charger, discharge and charge them a few times see how much mAh it give,s and takes and watch for voltage sag a bad cell will drop voltage quick once a load is put on it and maintained, the hobby charger will cutoff and stop if the cell,s voltage drops to low so there is no risk of over discharging.

old4570 wrote:

And many dedicated 18650 chargers do exactly the same thing ... [ Sensitive to the internal resistance of batteries - therefore terminating early ] 

And yes there are some chargers that force batteries to a higher voltage state , but depending on the school of thought ? 

There are those who believe in conditioning batteries , even Li-ion ..

And some Li-ion get better after some use ?  If you cant condition Li-ion, this should not happen  .

Can you bring back degraded cells ?  

One of these days , Im going to look into it , probably when school finishes , I will run some experiments , to see , condition new cells , or recondition old cells in any shape or form 

the internal resistance of batteries play,s a big part in charging dishcarging and when people do current draw test on torches, imo cheap dedicated chargers would be affected by this more but thats mo.

ive tryed to bring back a couple of bad li-ion,s and li-po,s they dont realy come back i must admit i didnt spend much time on it but the mAh never improved and the the internal resistance only whent up and the li-po,s puffed, but ive been able to bring nimh back to life as my hobby charger has some good modes for that.

a good test to do is c rate,s over time say have 4 batteries with the same or close to internal resistance of each other and charge one at 0.2 amp one at 0.5amp one at 1 amp and the last one at 2 amp and then over time record the internal resistance and the amount of mAh they take.

ive noticed the battery charged at 0.2 amp will take more mAh and have a lower internal resistance then the one charged at 2 amp over time.

this is why parrallel charging in my mind is not the best as the cells spike quickly and dishcarge and charge each other at upto 2c + for li-ions even though its only for a short period i belive this will raise the internal resistance of the battery sorten its life and over time it will be able to give less current.

this is why i belive balance charging in series is better, but people want faster charge methods they want to charge one or two batteries at 1 + amps each unless they are top self batteries it will raise internal resistance of the batteries, i think your better off charging at lower charge rates like 0.5 amps yes it will take a little bit longer then charging at 1 amp but if you charge 6 at a time then its much quicker.

just my thoughts im half asleep

E1320
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I would just like to confirm your results, I have noticed the same thing when testing batteries. I get them topped off completely with my TR-001 ~4.2v were my Accucell hobby charger leaves them a little off ~4.1v. I also get higher amperage readings from a battery that comes off the TR-001 compared to one that comes off the Accucell hobby charger. Thanks for confirming my suspicion.

I am already visualizing the duct tape over your mouth.

benckie
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E1320 i would do a test use the same charge rate on the Accucell hobby charger as the TR-001 and see how that turns out as i asume your using a higher charge rate on your hobby charger then your TR-001

i would also test your Accucell hobby charger as i found them like the imax,s to be off .04 volt + or - per cell and the voltage on the main charge leads to be the same.

if your Accucell hobby charger is saying the battery is 4.2v and it stops charging but you check it with your dmm and its 4.1 there is a good chance its not charging them to full and your TR-001 could be charging them to full or slightly over charging them.

this could also be why people are questioning there rested voltage of the cells after comming of there cheap hobby charger over charging (using to high amps) or inaccuracy or both

ChibiM
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Thanks for the info!

old4570
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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 ]  

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

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

old4570
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benckie wrote:

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 ... 

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

okwchin
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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. 

"like everyone else - I’m looking for my next “last” flashlight" -  ohnonothimagain

okwchin
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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.

"like everyone else - I’m looking for my next “last” flashlight" -  ohnonothimagain

jacktheclipper
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Very informative and useful , okwchin . Thanks .

What I do

 

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

 

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

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

old4570
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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 .

 

 

 

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

Boaz
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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

       καὶ τὸ φῶς ἐν τῇ σκοτίᾳ φαίνει καὶ ἡ σκοτία αὐτὸ οὐ κατέλαβεν

                            

       Dc-fix diffuser film  >…  http://budgetlightforum.com/node/42208

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Boaz wrote:

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 !  

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

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Hehe, more fun!

"like everyone else - I’m looking for my next “last” flashlight" -  ohnonothimagain

okwchin
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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.

"like everyone else - I’m looking for my next “last” flashlight" -  ohnonothimagain

okwchin
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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?

"like everyone else - I’m looking for my next “last” flashlight" -  ohnonothimagain

HKJ
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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.

 

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

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