On a sunny day (Thu, 18 Nov 2021 12:07:38 -0800 (PST)) it happened Ed Lee <edward.ming.lee@gmail.com> wrote in <2900a7d8-299d-4688-a026-92101cadc9b3n@googlegroups.com>:>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.OK, what I forgot to mention is the volatge drop (when charging current limited) that happens when the cell is full (there is a name for that, delta V or something?) and normally used by chargers to detect 'battery full'. Get your battery cherging curves from the internet (google). I have made charge curve pictures for all my battery types. nimh_charge_curve.png eneloop_800mAh_AAA_charge_discharge_curve.gif lifepo4_charge_curve.jpg etc
usb fast charger question
Started by ●November 17, 2021
Reply by ●November 19, 20212021-11-19
Reply by ●November 19, 20212021-11-19
On Thursday, November 18, 2021 at 11:48:09 PM UTC-8, Jan Panteltje wrote:> On a sunny day (Thu, 18 Nov 2021 12:07:38 -0800 (PST)) it happened Ed Lee > <edward....@gmail.com> wrote in > <2900a7d8-299d-4688...@googlegroups.com>: > >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. > OK, what I forgot to mention is the volatge drop (when charging current limited) > that happens when the cell is full (there is a name for that, delta V or something?) > and normally used by chargers to detect 'battery full'. > Get your battery cherging curves from the internet (google). > I have made charge curve pictures for all my battery types. > nimh_charge_curve.png > eneloop_800mAh_AAA_charge_discharge_curve.gif > lifepo4_charge_curve.jpg > etcI routinely charge at 2.5C (20% SOC) and 1C (60% SOC) for most 2Ahr cells. They hardly get warm at all, as long as the total charge time is short (15 minutes). With USB (5V) supply, you can hardly drive it over 1.5C (3A for 2Ahr cell). If the cell does not get warm, then most of the energy is stored instead of heating up due to "Internal Chemical Resistance to Charging". Heat is the biggest problem.
Reply by ●November 19, 20212021-11-19
On Friday, November 19, 2021 at 4:48:47 AM UTC-4, Ed Lee wrote:> On Thursday, November 18, 2021 at 11:48:09 PM UTC-8, Jan Panteltje wrote: > > On a sunny day (Thu, 18 Nov 2021 12:07:38 -0800 (PST)) it happened Ed Lee > > <edward....@gmail.com> wrote in > > <2900a7d8-299d-4688...@googlegroups.com>: > > >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. > > OK, what I forgot to mention is the volatge drop (when charging current limited) > > that happens when the cell is full (there is a name for that, delta V or something?) > > and normally used by chargers to detect 'battery full'. > > Get your battery cherging curves from the internet (google). > > I have made charge curve pictures for all my battery types. > > nimh_charge_curve.png > > eneloop_800mAh_AAA_charge_discharge_curve.gif > > lifepo4_charge_curve.jpg > > etc > I routinely charge at 2.5C (20% SOC) and 1C (60% SOC) for most 2Ahr cells. They hardly get warm at all, as long as the total charge time is short (15 minutes). With USB (5V) supply, you can hardly drive it over 1.5C (3A for 2Ahr cell). If the cell does not get warm, then most of the energy is stored instead of heating up due to "Internal Chemical Resistance to Charging". Heat is the biggest problem.Here you are showing you don't understand the difference between power and energy. Damage to the cells happen from the overcurrent regardless of the temperature. By your reasoning you should be able to pump the cell with 100C if you do it for a short enough time. One wear mechanism is plating of lithium on the graphite anode instead of lithium being intercalated. Intercalation is a reversible reaction while plating is not. Lithium is preferentially plated at higher currents. It doesn't matter that the current is short enough the battery temperature doesn't rise a lot. -- Rick C. --+ Get 1,000 miles of free Supercharging --+ Tesla referral code - https://ts.la/richard11209
Reply by ●November 19, 20212021-11-19
On a sunny day (Fri, 19 Nov 2021 00:48:44 -0800 (PST)) it happened Ed Lee <edward.ming.lee@gmail.com> wrote in <35a026ce-230f-4ea0-a094-01df8152bff0n@googlegroups.com>:>On Thursday, November 18, 2021 at 11:48:09 PM UTC-8, Jan Panteltje wrote: >> On a sunny day (Thu, 18 Nov 2021 12:07:38 -0800 (PST)) it happened Ed Lee >> ><edward....@gmail.com> wrote in >> <2900a7d8-299d-4688...@googlegroups.com>: >> >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. >> OK, what I forgot to mention is the volatge drop (when charging current limited) >> >that happens when the cell is full (there is a name for that, delta V or something?) >> >and normally used by chargers to detect 'battery full'. >> Get your battery cherging curves from the internet (google). >> I have made charge curve pictures for all my battery types. >> nimh_charge_curve.png >> eneloop_800mAh_AAA_charge_discharge_curve.gif >> lifepo4_charge_curve.jpg >> etc > >I routinely charge at 2.5C (20% SOC) and 1C (60% SOC) for most 2Ahr cells. >They hardly get warm at all, as long as the total charge time is short (15 >minutes). With USB (5V) supply, you can hardly drive it over 1.5C (3A for >2Ahr cell). If the cell does not get warm, then most of the energy is stored >instead of heating up due to "Internal Chemical Resistance to Charging". > Heat is the biggest problem.I try avoiding charging more than 1C to extend battery life (I hope). I have a bunch of 2 cell and 3 cell lipos for my drones. Those also need individual cell monitoring when charging, and I have a special charger for those. Those batteries do not last very long, discharge is high, >10A for a 2700mAh 7.4V 10C cell: http://panteltje.com/pub/hubsan_h501s_current_test_full_throttle_IMG_6290.JPG It does not matyter if charging takes a while, I have several so I can keep flying.
Reply by ●November 19, 20212021-11-19
On Friday, November 19, 2021 at 3:41:11 AM UTC-8, gnuarm.del...@gmail.com wrote:> On Friday, November 19, 2021 at 4:48:47 AM UTC-4, Ed Lee wrote: > > On Thursday, November 18, 2021 at 11:48:09 PM UTC-8, Jan Panteltje wrote: > > > On a sunny day (Thu, 18 Nov 2021 12:07:38 -0800 (PST)) it happened Ed Lee > > > <edward....@gmail.com> wrote in > > > <2900a7d8-299d-4688...@googlegroups.com>: > > > >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. > > > OK, what I forgot to mention is the volatge drop (when charging current limited) > > > that happens when the cell is full (there is a name for that, delta V or something?) > > > and normally used by chargers to detect 'battery full'. > > > Get your battery cherging curves from the internet (google). > > > I have made charge curve pictures for all my battery types. > > > nimh_charge_curve.png > > > eneloop_800mAh_AAA_charge_discharge_curve.gif > > > lifepo4_charge_curve.jpg > > > etc > > I routinely charge at 2.5C (20% SOC) and 1C (60% SOC) for most 2Ahr cells. They hardly get warm at all, as long as the total charge time is short (15 minutes). With USB (5V) supply, you can hardly drive it over 1.5C (3A for 2Ahr cell). If the cell does not get warm, then most of the energy is stored instead of heating up due to "Internal Chemical Resistance to Charging". Heat is the biggest problem. > Here you are showing you don't understand the difference between power and energy. Damage to the cells happen from the overcurrent regardless of the temperature. By your reasoning you should be able to pump the cell with 100C if you do it for a short enough time. > > One wear mechanism is plating of lithium on the graphite anode instead of lithium being intercalated. Intercalation is a reversible reaction while plating is not. Lithium is preferentially plated at higher currents. It doesn't matter that the current is short enough the battery temperature doesn't rise a lot.But we are not talking about 100C, just 2C. Highlights Harvested electrodes are tested at high discharge and charge rates. Several limiting processes were observed within a single 10 s pulse. In 10s pulses, the cathodes could be charged at 10C and stay below the 4.2 V limit. The anodes voltages went negative at 5C, but the limiting process was diffusion. Repeated pulsing with 20C, 10s pulses lead to lithium plating on the anodes. https://www.sciencedirect.com/science/article/pii/S0378775321002330
Reply by ●November 19, 20212021-11-19
On Friday, November 19, 2021 at 11:28:37 AM UTC-4, Ed Lee wrote:> On Friday, November 19, 2021 at 3:41:11 AM UTC-8, gnuarm.del...@gmail.com wrote: > > On Friday, November 19, 2021 at 4:48:47 AM UTC-4, Ed Lee wrote: > > > On Thursday, November 18, 2021 at 11:48:09 PM UTC-8, Jan Panteltje wrote: > > > > On a sunny day (Thu, 18 Nov 2021 12:07:38 -0800 (PST)) it happened Ed Lee > > > > <edward....@gmail.com> wrote in > > > > <2900a7d8-299d-4688...@googlegroups.com>: > > > > >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. > > > > OK, what I forgot to mention is the volatge drop (when charging current limited) > > > > that happens when the cell is full (there is a name for that, delta V or something?) > > > > and normally used by chargers to detect 'battery full'. > > > > Get your battery cherging curves from the internet (google). > > > > I have made charge curve pictures for all my battery types. > > > > nimh_charge_curve.png > > > > eneloop_800mAh_AAA_charge_discharge_curve.gif > > > > lifepo4_charge_curve.jpg > > > > etc > > > I routinely charge at 2.5C (20% SOC) and 1C (60% SOC) for most 2Ahr cells. They hardly get warm at all, as long as the total charge time is short (15 minutes). With USB (5V) supply, you can hardly drive it over 1.5C (3A for 2Ahr cell). If the cell does not get warm, then most of the energy is stored instead of heating up due to "Internal Chemical Resistance to Charging". Heat is the biggest problem. > > Here you are showing you don't understand the difference between power and energy. Damage to the cells happen from the overcurrent regardless of the temperature. By your reasoning you should be able to pump the cell with 100C if you do it for a short enough time. > > > > One wear mechanism is plating of lithium on the graphite anode instead of lithium being intercalated. Intercalation is a reversible reaction while plating is not. Lithium is preferentially plated at higher currents. It doesn't matter that the current is short enough the battery temperature doesn't rise a lot. > But we are not talking about 100C, just 2C. > > Highlights > Harvested electrodes are tested at high discharge and charge rates. > Several limiting processes were observed within a single 10 s pulse. > In 10s pulses, the cathodes could be charged at 10C and stay below the 4.2 V limit. > The anodes voltages went negative at 5C, but the limiting process was diffusion. > Repeated pulsing with 20C, 10s pulses lead to lithium plating on the anodes. > > https://www.sciencedirect.com/science/article/pii/S0378775321002330Ok, I give up. No point in talking when no one is listening. -- Rick C. -+- Get 1,000 miles of free Supercharging -+- Tesla referral code - https://ts.la/richard11209
Reply by ●November 19, 20212021-11-19
On Friday, November 19, 2021 at 3:43:36 PM UTC-8, gnuarm.del...@gmail.com wrote:> On Friday, November 19, 2021 at 11:28:37 AM UTC-4, Ed Lee wrote: > > On Friday, November 19, 2021 at 3:41:11 AM UTC-8, gnuarm.del...@gmail.com wrote: > > > On Friday, November 19, 2021 at 4:48:47 AM UTC-4, Ed Lee wrote: > > > > On Thursday, November 18, 2021 at 11:48:09 PM UTC-8, Jan Panteltje wrote: > > > > > On a sunny day (Thu, 18 Nov 2021 12:07:38 -0800 (PST)) it happened Ed Lee > > > > > <edward....@gmail.com> wrote in > > > > > <2900a7d8-299d-4688...@googlegroups.com>: > > > > > >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. > > > > > OK, what I forgot to mention is the volatge drop (when charging current limited) > > > > > that happens when the cell is full (there is a name for that, delta V or something?) > > > > > and normally used by chargers to detect 'battery full'. > > > > > Get your battery cherging curves from the internet (google). > > > > > I have made charge curve pictures for all my battery types. > > > > > nimh_charge_curve.png > > > > > eneloop_800mAh_AAA_charge_discharge_curve.gif > > > > > lifepo4_charge_curve.jpg > > > > > etc > > > > I routinely charge at 2.5C (20% SOC) and 1C (60% SOC) for most 2Ahr cells. They hardly get warm at all, as long as the total charge time is short (15 minutes). With USB (5V) supply, you can hardly drive it over 1.5C (3A for 2Ahr cell). If the cell does not get warm, then most of the energy is stored instead of heating up due to "Internal Chemical Resistance to Charging". Heat is the biggest problem. > > > Here you are showing you don't understand the difference between power and energy. Damage to the cells happen from the overcurrent regardless of the temperature. By your reasoning you should be able to pump the cell with 100C if you do it for a short enough time. > > > > > > One wear mechanism is plating of lithium on the graphite anode instead of lithium being intercalated. Intercalation is a reversible reaction while plating is not. Lithium is preferentially plated at higher currents. It doesn't matter that the current is short enough the battery temperature doesn't rise a lot. > > But we are not talking about 100C, just 2C. > > > > Highlights > > Harvested electrodes are tested at high discharge and charge rates. > > Several limiting processes were observed within a single 10 s pulse. > > In 10s pulses, the cathodes could be charged at 10C and stay below the 4.2 V limit. > > The anodes voltages went negative at 5C, but the limiting process was diffusion. > > Repeated pulsing with 20C, 10s pulses lead to lithium plating on the anodes. > > > > https://www.sciencedirect.com/science/article/pii/S0378775321002330 > Ok, I give up. No point in talking when no one is listening.I listen to facts. They tested 5000 cycles of 20C for 10s and find lithium plating on the anode. I don't know how much it would degrade, but sound like it would take a while to cause problem. Anyway, i am not even getting close to 20C and even if i cycle it everyday, it would last 10 years.
