usb fast charger question

On Thursday, November 18, 2021 at 10:50:51 AM UTC-8, gnuarm.del...@gmail.com wrote:
> On Thursday, November 18, 2021 at 10:53:33 AM UTC-4, Ed Lee wrote: 
> > On Thursday, November 18, 2021 at 6:28:59 AM UTC-8, gnuarm.del...@gmail.com wrote: 
> > > On Wednesday, November 17, 2021 at 10:11:48 PM UTC-4, Ed Lee wrote: 
> > > > On Wednesday, November 17, 2021 at 5:18:47 PM UTC-8, T wrote: 
> > > > > On 11/17/21 07:30, Ed Lee wrote: 
> > > > > > On Wednesday, November 17, 2021 at 2:15:43 AM UTC-8, Carlos E. R. wrote: 
> > > > > >> On 17/11/2021 08.58, T wrote: 
> > > > > >>> Hi All, 
> > > > > >>> 
> > > > > >>> I asked about the voltage of a USB fast charger. I got back: 
> > > > > >>> 
> > > > > >>> 5V-3A, 9V-3A, 12V-3A, 15V-3A, 20V-3A 
> > > > > >>> 
> > > > > >>> My Android tablet wants 5.2V, 2.0 A 
> > > > > >>> 
> > > > > >>> 
> > > > > >>> Uhhhh. Is there something about the USB cable that 
> > > > > >>> tell the charger not to fry what I plug it into? 
> > > > > >> Not the cable. The voltage is negotiated between the device and the 
> > > > > >> charger. Before that, you only have "1 Load unit" available. 
> > > > > > 
> > > > > > There is very limited voltage range to negotiate anyway. 
> > > > > > 
> > > > > > The 3A rating is mainly to protect the cable and connector, so that you don't drive 3A through a 2A device. 
> > > > > > 
> > > > > > As for the battery, nothing wrong with 1.5C charging, although 1C is the optimized rate. 
> > > > > > 
> > > > > > 
> > > > > I am not following. How does the charging block 
> > > > > know what voltage and current is allowed? Is 
> > > > > the charging block a constant current device 
> > > > > that clips at 5V? 
> > > > The charging current is limited by the internal resistance of the battery. 
> > > WRONG! The device being charged is responsible for supplying the right voltage to the battery by either a series dropper or a switching converter. 
> > Whatever the voltage is supplied, it's still limited by the internal resistance. At 60% SOC, most of the cells i tested have around 1/4 ohms at 4.3V voltage source. My voltage source supplies a constant voltage of 4.3V, but the cell won't draw more than 2A.
> You do this all the time. You completely muck up the topic as if you knew nothing at all about electronics. What current will flow into your battery at 4.4V? How about 4.5V? How about 5V? There is nothing that says the voltage is set to a single value. As I've said, batteries are often initially charged at a rate set by current rather than voltage.
> > > As has been described in this forum many times, typical charging profiles use an initial constant current until reaching some voltage level followed by a constant voltage charge with the current tapering off. 
> > I am using constant voltage source of 4.3V with up to 5A. My charging profile is: 
> > 
> > 20% to 30%, 5A in 2 minutes 
> > 30% to 40%, 5A in 2 minutes 
> > 40% to 50%, 3A in 7 minutes 
> > 50% to 60%, 2A in 15 minutes 
> > 
> > I am only using 40% (20% to 60% SOC) of the capabilities, but that's OK.
> No one cares what you are doing. Normal devices use an internal charger matched to the battery so as to not overcharge it either by voltage or current. I've always heard that 1C is optimal (low wear and yet fast) meaning 1 hour, but that is a current setting and only provides a portion of the charge before it is switched to voltage control. In the voltage control stage the current drops off asymptotically and so can take a larger share of the charging time compared to the current controlled phase for the amount of charge provided. Lithium batteries suffer most of their wear in the final 10 to 20% of the charging cycle, so not topping off not only saves time it gives the batteries a longer life.
> > > In the case of lead-acid batteries once the current drops to some level the voltage is lowered a bit supplying a "float" charge at a low, continuous current without harming the battery. Lithium cells aren't provided with a float current. 
> > > > So, it's OK to hook up a 2A device to a 3A charger. 
> > > That is correct, but not for the reason you gave. 
> > I am hooking up a 2A device to a 5A charger, no other limitations except with internal resistance.
> No one cares what you are doing. You are not a phone or other electronic device which is what was being discussed when you made your erroneous statement. 

Fine.  Nobody needs to follow what i do.  All i am saying it that beyond 60% SOC, internal resistance is the thing limiting charging rate.  It doesn't matter what voltage you are setting.  The charging rate is limited by IR.  You are saying charger is the limiting factor, but in fact it is trying to avoid the real limiting factor: internal resistance.

On Thursday, 18 November 2021 at 11:06:35 UTC-8, Ed Lee wrote:
...
> Fine. Nobody needs to follow what i do. All i am saying it that beyond 60% SOC, internal resistance is the thing limiting charging rate. It doesn't matter what voltage you are setting. The charging rate is limited by IR. You are saying charger is the limiting factor, but in fact it is trying to avoid the real limiting factor: internal resistance.

Yes, beyond about 50-60% SOC the charger would typically use constant voltage charging where the internal resistance does control the charging current. However, the current is still being measured by the charging circuit and if it attempted to go above the limit set by the battery or the source the charger it would go back into constant-current mode.

The ultimate limit is not the current determined by the internal resistance but that determined by the battery characteristics, temperature, and power source etc. For example, at low temperatures, the charger would dictate a lower charging current and reduce the terminal voltage to meet that current limit.

kw

On Thursday, November 18, 2021 at 3:06:35 PM UTC-4, Ed Lee wrote:
> On Thursday, November 18, 2021 at 10:50:51 AM UTC-8, gnuarm.del...@gmail.com wrote: 
> > On Thursday, November 18, 2021 at 10:53:33 AM UTC-4, Ed Lee wrote: 
> > > On Thursday, November 18, 2021 at 6:28:59 AM UTC-8, gnuarm.del...@gmail.com wrote: 
> > > > On Wednesday, November 17, 2021 at 10:11:48 PM UTC-4, Ed Lee wrote: 
> > > > > On Wednesday, November 17, 2021 at 5:18:47 PM UTC-8, T wrote: 
> > > > > > On 11/17/21 07:30, Ed Lee wrote: 
> > > > > > > On Wednesday, November 17, 2021 at 2:15:43 AM UTC-8, Carlos E. R. wrote: 
> > > > > > >> On 17/11/2021 08.58, T wrote: 
> > > > > > >>> Hi All, 
> > > > > > >>> 
> > > > > > >>> I asked about the voltage of a USB fast charger. I got back: 
> > > > > > >>> 
> > > > > > >>> 5V-3A, 9V-3A, 12V-3A, 15V-3A, 20V-3A 
> > > > > > >>> 
> > > > > > >>> My Android tablet wants 5.2V, 2.0 A 
> > > > > > >>> 
> > > > > > >>> 
> > > > > > >>> Uhhhh. Is there something about the USB cable that 
> > > > > > >>> tell the charger not to fry what I plug it into? 
> > > > > > >> Not the cable. The voltage is negotiated between the device and the 
> > > > > > >> charger. Before that, you only have "1 Load unit" available. 
> > > > > > > 
> > > > > > > There is very limited voltage range to negotiate anyway. 
> > > > > > > 
> > > > > > > The 3A rating is mainly to protect the cable and connector, so that you don't drive 3A through a 2A device. 
> > > > > > > 
> > > > > > > As for the battery, nothing wrong with 1.5C charging, although 1C is the optimized rate. 
> > > > > > > 
> > > > > > > 
> > > > > > I am not following. How does the charging block 
> > > > > > know what voltage and current is allowed? Is 
> > > > > > the charging block a constant current device 
> > > > > > that clips at 5V? 
> > > > > The charging current is limited by the internal resistance of the battery. 
> > > > WRONG! The device being charged is responsible for supplying the right voltage to the battery by either a series dropper or a switching converter. 
> > > Whatever the voltage is supplied, it's still limited by the internal resistance. At 60% SOC, most of the cells i tested have around 1/4 ohms at 4.3V voltage source. My voltage source supplies a constant voltage of 4.3V, but the cell won't draw more than 2A. 
> > You do this all the time. You completely muck up the topic as if you knew nothing at all about electronics. What current will flow into your battery at 4.4V? How about 4.5V? How about 5V? There is nothing that says the voltage is set to a single value. As I've said, batteries are often initially charged at a rate set by current rather than voltage. 
> > > > As has been described in this forum many times, typical charging profiles use an initial constant current until reaching some voltage level followed by a constant voltage charge with the current tapering off. 
> > > I am using constant voltage source of 4.3V with up to 5A. My charging profile is: 
> > > 
> > > 20% to 30%, 5A in 2 minutes 
> > > 30% to 40%, 5A in 2 minutes 
> > > 40% to 50%, 3A in 7 minutes 
> > > 50% to 60%, 2A in 15 minutes 
> > > 
> > > I am only using 40% (20% to 60% SOC) of the capabilities, but that's OK. 
> > No one cares what you are doing. Normal devices use an internal charger matched to the battery so as to not overcharge it either by voltage or current. I've always heard that 1C is optimal (low wear and yet fast) meaning 1 hour, but that is a current setting and only provides a portion of the charge before it is switched to voltage control. In the voltage control stage the current drops off asymptotically and so can take a larger share of the charging time compared to the current controlled phase for the amount of charge provided. Lithium batteries suffer most of their wear in the final 10 to 20% of the charging cycle, so not topping off not only saves time it gives the batteries a longer life. 
> > > > In the case of lead-acid batteries once the current drops to some level the voltage is lowered a bit supplying a "float" charge at a low, continuous current without harming the battery. Lithium cells aren't provided with a float current. 
> > > > > So, it's OK to hook up a 2A device to a 3A charger. 
> > > > That is correct, but not for the reason you gave. 
> > > I am hooking up a 2A device to a 5A charger, no other limitations except with internal resistance. 
> > No one cares what you are doing. You are not a phone or other electronic device which is what was being discussed when you made your erroneous statement.
> Fine. Nobody needs to follow what i do. All i am saying it that beyond 60% SOC, internal resistance is the thing limiting charging rate. It doesn't matter what voltage you are setting. The charging rate is limited by IR. You are saying charger is the limiting factor, but in fact it is trying to avoid the real limiting factor: internal resistance.

"It doesn't matter what voltage you are setting."  Now you are showing ignorance of Ohm's law.  I can't help you.  You literally won't listen to anything anyone says that doesn't agree with you. 

-- 

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

On Thursday, November 18, 2021 at 3:16:50 PM UTC-4, ke...@kjwdesigns.com wrote:
> On Thursday, 18 November 2021 at 11:06:35 UTC-8, Ed Lee wrote: 
> ...
> > Fine. Nobody needs to follow what i do. All i am saying it that beyond 60% SOC, internal resistance is the thing limiting charging rate. It doesn't matter what voltage you are setting. The charging rate is limited by IR. You are saying charger is the limiting factor, but in fact it is trying to avoid the real limiting factor: internal resistance.
> Yes, beyond about 50-60% SOC the charger would typically use constant voltage charging where the internal resistance does control the charging current. However, the current is still being measured by the charging circuit and if it attempted to go above the limit set by the battery or the source the charger it would go back into constant-current mode. 
> 
> The ultimate limit is not the current determined by the internal resistance but that determined by the battery characteristics, temperature, and power source etc. For example, at low temperatures, the charger would dictate a lower charging current and reduce the terminal voltage to meet that current limit. 

Often people forget that Ohm's law is just a relationship between the current and voltage in a circuit.  We define the resistance by the ratio of voltage and current.  The battery internal chemical operation is what defines the current flow at a voltage.  We like to think we can describe this by Ohm's law, but for batteries it is a poor fit and is much more complex as you indicate by the variation with temperature for example.  It will also vary significantly over time, not just as the battery charges, but when the battery is resting.  Charge and measure the parameters, let it set and measure again and they will be different.  That's why the internal resistance is not so useful.  A battery is not a voltage source with a resistor.  It is a chemical reaction with electrical properties. 

-- 

Rick C.

+- Get 1,000 miles of free Supercharging
+- Tesla referral code - https://ts.la/richard11209

On Thursday, November 18, 2021 at 11:33:26 AM UTC-8, gnuarm.del...@gmail.com wrote:
> On Thursday, November 18, 2021 at 3:16:50 PM UTC-4, ke...@kjwdesigns.com wrote: 
> > On Thursday, 18 November 2021 at 11:06:35 UTC-8, Ed Lee wrote: 
> > ... 
> > > Fine. Nobody needs to follow what i do. All i am saying it that beyond 60% SOC, internal resistance is the thing limiting charging rate. It doesn't matter what voltage you are setting. The charging rate is limited by IR. You are saying charger is the limiting factor, but in fact it is trying to avoid the real limiting factor: internal resistance. 
> > Yes, beyond about 50-60% SOC the charger would typically use constant voltage charging where the internal resistance does control the charging current. However, the current is still being measured by the charging circuit and if it attempted to go above the limit set by the battery or the source the charger it would go back into constant-current mode. 
> > 
> > The ultimate limit is not the current determined by the internal resistance but that determined by the battery characteristics, temperature, and power source etc. For example, at low temperatures, the charger would dictate a lower charging current and reduce the terminal voltage to meet that current limit.
> Often people forget that Ohm's law is just a relationship between the current and voltage in a circuit. We define the resistance by the ratio of voltage and current. The battery internal chemical operation is what defines the current flow at a voltage. We like to think we can describe this by Ohm's law, but for batteries it is a poor fit and is much more complex as you indicate by the variation with temperature for example. It will also vary significantly over time, not just as the battery charges, but when the battery is resting. Charge and measure the parameters, let it set and measure again and they will be different. That's why the internal resistance is not so useful. A battery is not a voltage source with a resistor. It is a chemical reaction with electrical properties. 

Battery internal resistance is a function of SOC and temp, not a fixed resistor.  Resistance is defined as turning voltage and current into heat, rather than charge storage.  Fine, if you want to call it something else, but i see it as internal resistance to charging.

On a sunny day (Thu, 18 Nov 2021 11:16:46 -0800 (PST)) it happened
"ke...@kjwdesigns.com" <keith@kjwdesigns.com> wrote in
<0a51460d-1038-47c7-8250-5f6b6dd260b5n@googlegroups.com>:

>On Thursday, 18 November 2021 at 11:06:35 UTC-8, Ed Lee wrote:
>...
>> Fine. Nobody needs to follow what i do. All i am saying it that beyond 60%
>SOC, internal resistance is the thing limiting charging rate. It doesn't matter
>what voltage you are setting. The charging rate is limited by IR. You
>are saying charger is the limiting factor, but in fact it is trying to avoid
>the real limiting factor: internal resistance.
>
>Yes, beyond about 50-60% SOC the charger would typically use constant voltage
>charging where the internal resistance does control the charging current.
>However, the current is still being measured by the charging circuit and if
>it attempted to go above the limit set by the battery or the source the charger
>it would go back into constant-current mode.
>
>The ultimate limit is not the current determined by the internal resistance
>but that determined by the battery characteristics, temperature, and power
>source etc. For example, at low temperatures, the charger would dictate a lower
>charging current and reduce the terminal voltage to meet that current
>limit.
>
>kw

I usually charge batteries on my lab supply (set voltage and curent limit),
for example with eneloop 1.5V AAA charging at 1.6V 1C you will see a clear temperature rise when the cell is full.
Normally one should measure that and switch the charger off.

On Thursday, November 18, 2021 at 11:53:24 AM UTC-8, Jan Panteltje wrote:
> On a sunny day (Thu, 18 Nov 2021 11:16:46 -0800 (PST)) it happened 
> "ke...@kjwdesigns.com" <ke...@kjwdesigns.com> wrote in 
> <0a51460d-1038-47c7...@googlegroups.com>:
> >On Thursday, 18 November 2021 at 11:06:35 UTC-8, Ed Lee wrote: 
> >... 
> >> Fine. Nobody needs to follow what i do. All i am saying it that beyond 60% 
> >SOC, internal resistance is the thing limiting charging rate. It doesn't matter 
> >what voltage you are setting. The charging rate is limited by IR. You 
> >are saying charger is the limiting factor, but in fact it is trying to avoid 
> >the real limiting factor: internal resistance. 
> > 
> >Yes, beyond about 50-60% SOC the charger would typically use constant voltage 
> >charging where the internal resistance does control the charging current. 
> >However, the current is still being measured by the charging circuit and if 
> >it attempted to go above the limit set by the battery or the source the charger 
> >it would go back into constant-current mode. 
> > 
> >The ultimate limit is not the current determined by the internal resistance 
> >but that determined by the battery characteristics, temperature, and power 
> >source etc. For example, at low temperatures, the charger would dictate a lower 
> >charging current and reduce the terminal voltage to meet that current 
> >limit. 
> > 
> >kw
> I usually charge batteries on my lab supply (set voltage and curent limit), 
> for example with eneloop 1.5V AAA charging at 1.6V 1C you will see a clear temperature rise when the cell is full. 
> Normally one should measure that and switch the charger off.

There are charging ASIC that will fully charge cells to 100% with auto shut-off, but problem is that it only charge at maximum of 300mA and it would take hours to charge.

My current device must be charged in 15 minutes or less; so, just a fixed voltage source using 40% capacity of the cell.  Beyond that, the "Internal Chemical Resistance to Charging" limits the charging rate.  Don't call it Internal Resistance, as per Internet Police.

On Thursday, November 18, 2021 at 4:07:41 PM UTC-4, Ed Lee wrote:
> On Thursday, November 18, 2021 at 11:53:24 AM UTC-8, Jan Panteltje wrote: 
> > On a sunny day (Thu, 18 Nov 2021 11:16:46 -0800 (PST)) it happened 
> > "ke...@kjwdesigns.com" <ke...@kjwdesigns.com> wrote in 
> > <0a51460d-1038-47c7...@googlegroups.com>: 
> > >On Thursday, 18 November 2021 at 11:06:35 UTC-8, Ed Lee wrote: 
> > >... 
> > >> Fine. Nobody needs to follow what i do. All i am saying it that beyond 60% 
> > >SOC, internal resistance is the thing limiting charging rate. It doesn't matter 
> > >what voltage you are setting. The charging rate is limited by IR. You 
> > >are saying charger is the limiting factor, but in fact it is trying to avoid 
> > >the real limiting factor: internal resistance. 
> > > 
> > >Yes, beyond about 50-60% SOC the charger would typically use constant voltage 
> > >charging where the internal resistance does control the charging current. 
> > >However, the current is still being measured by the charging circuit and if 
> > >it attempted to go above the limit set by the battery or the source the charger 
> > >it would go back into constant-current mode. 
> > > 
> > >The ultimate limit is not the current determined by the internal resistance 
> > >but that determined by the battery characteristics, temperature, and power 
> > >source etc. For example, at low temperatures, the charger would dictate a lower 
> > >charging current and reduce the terminal voltage to meet that current 
> > >limit. 
> > > 
> > >kw 
> > I usually charge batteries on my lab supply (set voltage and curent limit), 
> > for example with eneloop 1.5V AAA charging at 1.6V 1C you will see a clear temperature rise when the cell is full. 
> > Normally one should measure that and switch the charger off.
> There are charging ASIC that will fully charge cells to 100% with auto shut-off, but problem is that it only charge at maximum of 300mA and it would take hours to charge. 
> 
> My current device must be charged in 15 minutes or less; so, just a fixed voltage source using 40% capacity of the cell. Beyond that, the "Internal Chemical Resistance to Charging" limits the charging rate. Don't call it Internal Resistance, as per Internet Police.
 
You can never try to understand what someone is telling you.  The internal resistance does not limit the current absolutely.  You said you were charging at 4.35V or something.  Up the voltage and you will see a faster charge rate.  You may not like the accelerated wear, but it will charge faster.  Even a 15 minute charge rate is likely to wear the cells faster unless they are specially designed to charge fast. 

-- 

Rick C.

++ Get 1,000 miles of free Supercharging
++ Tesla referral code - https://ts.la/richard11209

On Thursday, November 18, 2021 at 1:26:54 PM UTC-8, gnuarm.del...@gmail.com wrote:
> On Thursday, November 18, 2021 at 4:07:41 PM UTC-4, Ed Lee wrote: 
> > On Thursday, November 18, 2021 at 11:53:24 AM UTC-8, Jan Panteltje wrote: 
> > > On a sunny day (Thu, 18 Nov 2021 11:16:46 -0800 (PST)) it happened 
> > > "ke...@kjwdesigns.com" <ke...@kjwdesigns.com> wrote in 
> > > <0a51460d-1038-47c7...@googlegroups.com>: 
> > > >On Thursday, 18 November 2021 at 11:06:35 UTC-8, Ed Lee wrote: 
> > > >... 
> > > >> Fine. Nobody needs to follow what i do. All i am saying it that beyond 60% 
> > > >SOC, internal resistance is the thing limiting charging rate. It doesn't matter 
> > > >what voltage you are setting. The charging rate is limited by IR. You 
> > > >are saying charger is the limiting factor, but in fact it is trying to avoid 
> > > >the real limiting factor: internal resistance. 
> > > > 
> > > >Yes, beyond about 50-60% SOC the charger would typically use constant voltage 
> > > >charging where the internal resistance does control the charging current. 
> > > >However, the current is still being measured by the charging circuit and if 
> > > >it attempted to go above the limit set by the battery or the source the charger 
> > > >it would go back into constant-current mode. 
> > > > 
> > > >The ultimate limit is not the current determined by the internal resistance 
> > > >but that determined by the battery characteristics, temperature, and power 
> > > >source etc. For example, at low temperatures, the charger would dictate a lower 
> > > >charging current and reduce the terminal voltage to meet that current 
> > > >limit. 
> > > > 
> > > >kw 
> > > I usually charge batteries on my lab supply (set voltage and curent limit), 
> > > for example with eneloop 1.5V AAA charging at 1.6V 1C you will see a clear temperature rise when the cell is full. 
> > > Normally one should measure that and switch the charger off. 
> > There are charging ASIC that will fully charge cells to 100% with auto shut-off, but problem is that it only charge at maximum of 300mA and it would take hours to charge. 
> > 
> > My current device must be charged in 15 minutes or less; so, just a fixed voltage source using 40% capacity of the cell. Beyond that, the "Internal Chemical Resistance to Charging" limits the charging rate. Don't call it Internal Resistance, as per Internet Police.
> You can never try to understand what someone is telling you. The internal resistance does not limit the current absolutely. You said you were charging at 4.35V or something. Up the voltage and you will see a faster charge rate. You may not like the accelerated wear, but it will charge faster. Even a 15 minute charge r ate is likely to wear the cells faster unless they are specially designed to charge fast. 

The voltage source is not easily adjustable.  Increasing voltage also runs the risk of overcharging the cell.   At 4.3V, it will fully charge the cell after days, if left connected accidentally.  The device will not be cycled often; so, wearing it out at 2C or 3C should not be a problem.

On Thursday, November 18, 2021 at 5:44:28 PM UTC-4, Ed Lee wrote:
> On Thursday, November 18, 2021 at 1:26:54 PM UTC-8, gnuarm.del...@gmail.com wrote: 
> > On Thursday, November 18, 2021 at 4:07:41 PM UTC-4, Ed Lee wrote: 
> > > On Thursday, November 18, 2021 at 11:53:24 AM UTC-8, Jan Panteltje wrote: 
> > > > On a sunny day (Thu, 18 Nov 2021 11:16:46 -0800 (PST)) it happened 
> > > > "ke...@kjwdesigns.com" <ke...@kjwdesigns.com> wrote in 
> > > > <0a51460d-1038-47c7...@googlegroups.com>: 
> > > > >On Thursday, 18 November 2021 at 11:06:35 UTC-8, Ed Lee wrote: 
> > > > >... 
> > > > >> Fine. Nobody needs to follow what i do. All i am saying it that beyond 60% 
> > > > >SOC, internal resistance is the thing limiting charging rate. It doesn't matter 
> > > > >what voltage you are setting. The charging rate is limited by IR. You 
> > > > >are saying charger is the limiting factor, but in fact it is trying to avoid 
> > > > >the real limiting factor: internal resistance. 
> > > > > 
> > > > >Yes, beyond about 50-60% SOC the charger would typically use constant voltage 
> > > > >charging where the internal resistance does control the charging current. 
> > > > >However, the current is still being measured by the charging circuit and if 
> > > > >it attempted to go above the limit set by the battery or the source the charger 
> > > > >it would go back into constant-current mode. 
> > > > > 
> > > > >The ultimate limit is not the current determined by the internal resistance 
> > > > >but that determined by the battery characteristics, temperature, and power 
> > > > >source etc. For example, at low temperatures, the charger would dictate a lower 
> > > > >charging current and reduce the terminal voltage to meet that current 
> > > > >limit. 
> > > > > 
> > > > >kw 
> > > > I usually charge batteries on my lab supply (set voltage and curent limit), 
> > > > for example with eneloop 1.5V AAA charging at 1.6V 1C you will see a clear temperature rise when the cell is full. 
> > > > Normally one should measure that and switch the charger off. 
> > > There are charging ASIC that will fully charge cells to 100% with auto shut-off, but problem is that it only charge at maximum of 300mA and it would take hours to charge. 
> > > 
> > > My current device must be charged in 15 minutes or less; so, just a fixed voltage source using 40% capacity of the cell. Beyond that, the "Internal Chemical Resistance to Charging" limits the charging rate. Don't call it Internal Resistance, as per Internet Police.
> > You can never try to understand what someone is telling you. The internal resistance does not limit the current absolutely. You said you were charging at 4.35V or something. Up the voltage and you will see a faster charge rate. You may not like the accelerated wear, but it will charge faster. Even a 15 minute charge r ate is likely to wear the cells faster unless they are specially designed to charge fast. 
> 
> The voltage source is not easily adjustable. Increasing voltage also runs the risk of overcharging the cell. At 4.3V, it will fully charge the cell after days, if left connected accidentally. The device will not be cycled often; so, wearing it out at 2C or 3C should not be a problem.

I'm not suggesting you should do anything.  I'm trying to get you to understand that what you are saying is not factual.  You are trying to tell others wrong information.  You can never get your head out of your own details to understand the conversation you are in.  

That's all I have to say on the matter.  Enjoy. 

-- 

Rick C.

--- Get 1,000 miles of free Supercharging
--- Tesla referral code - https://ts.la/richard11209