On Thursday, November 18, 2021 at 7:31:15 AM UTC-8, ke...@kjwdesigns.com wrote:> On Thursday, 18 November 2021 at 06:53:33 UTC-8, Ed Lee wrote: > ... > > 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. > > > 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. > But that's not the way the chargers work in devices such as tablets, phones, and cars.Not for slow chargers. But even DC fast chargers for car are limited by internal resistance. Beyond 60%, you can't pump any more reasonable voltage into the battery. Charging rate is dictated by internal resistance.> > They do as Rick says, constant current controlled charging until the target voltage is reached then they switch to constant voltage. By then the current has dropped to a fairly low value, maybe 0.5C.Because the effective internal resistance is so high. Current has to be lowered.> They are never in a condition that the battery resistance limits the current.Yes it is, when SOC is over 60%.
usb fast charger question
Started by ●November 17, 2021
Reply by ●November 18, 20212021-11-18
Reply by ●November 18, 20212021-11-18
On 11/17/2021 10:15 PM, Ed Lee wrote:> I am pumping 2A into a 2000mAhr cell at 4.3V when connected, and 3.8V open circuit. ... The only thing limiting my charging rate is the internal resistance. > ...How do you know that it's the internal resistance that's limiting the current and not internal charging circuitry? I think that you jumping to the simple/easy conclusion while the reality is much different.
Reply by ●November 18, 20212021-11-18
On Thursday, November 18, 2021 at 7:47:44 AM UTC-8, bobenge...@gmail.com wrote:> On 11/17/2021 10:15 PM, Ed Lee wrote: > > > I am pumping 2A into a 2000mAhr cell at 4.3V when connected, and 3.8V open circuit. ... The only thing limiting my charging rate is the internal resistance. > > ... > > How do you know that it's the internal resistance that's limiting the > current and not internal charging circuitry? I think that you jumping > to the simple/easy conclusion while the reality is much different.There is nothing else between my voltage source and cell. When connected, the voltage is at 4.3V, when separated, the cell voltage is at 3.8V. There is no other internal circuitry.
Reply by ●November 18, 20212021-11-18
On Wednesday, 17 November 2021 at 22:05:31 UTC-8, Jan Panteltje wrote:> Langwadt Christensen <lang...@fonz.dk> wrote in > <f7e5d494-a50f-46e7...@googlegroups.com>: > >if it is regular USB it is just 5V an the device will draw as much current as it needs up to the 2A USB charging limit > Old USB is limited to 500mA and does not communicate.... Most USB chargers didn't stick to the standard. Typically they could output currents up to their capability and would indicate that to the device by doing things such as shorting the data lines or using resistors to set a specific voltage. Samsung and Apple did it differently. kw
Reply by ●November 18, 20212021-11-18
On 18/11/2021 16.51, Ed Lee wrote:> On Thursday, November 18, 2021 at 7:47:44 AM UTC-8, bobenge...@gmail.com wrote: >> On 11/17/2021 10:15 PM, Ed Lee wrote: >> >>> I am pumping 2A into a 2000mAhr cell at 4.3V when connected, and 3.8V open circuit. ... The only thing limiting my charging rate is the internal resistance. >>> ... >> >> How do you know that it's the internal resistance that's limiting the >> current and not internal charging circuitry? I think that you jumping >> to the simple/easy conclusion while the reality is much different. > > There is nothing else between my voltage source and cell. When connected, the voltage is at 4.3V, when separated, the cell voltage is at 3.8V. There is no other internal circuitry.Except that the cell itself can have circuitry. -- Cheers, Carlos.
Reply by ●November 18, 20212021-11-18
On Thursday, November 18, 2021 at 9:04:11 AM UTC-8, Carlos E.R. wrote:> On 18/11/2021 16.51, Ed Lee wrote: > > On Thursday, November 18, 2021 at 7:47:44 AM UTC-8, bobenge...@gmail.com wrote: > >> On 11/17/2021 10:15 PM, Ed Lee wrote: > >> > >>> I am pumping 2A into a 2000mAhr cell at 4.3V when connected, and 3.8V open circuit. ... The only thing limiting my charging rate is the internal resistance. > >>> ... > >> > >> How do you know that it's the internal resistance that's limiting the > >> current and not internal charging circuitry? I think that you jumping > >> to the simple/easy conclusion while the reality is much different. > > > > There is nothing else between my voltage source and cell. When connected, the voltage is at 4.3V, when separated, the cell voltage is at 3.8V. There is no other internal circuitry. > Except that the cell itself can have circuitry.No, they are bare cells. I opened up some just to be sure. If the cell cannot store more charges and turn them into heat, then by definition is the internal resistance. Most chargers avoid it by lowering the voltage or current, but doesn't mean the IR limitation is not there. Are cars driving at 55MPH because the cops are there, or because there is a speed limit?
Reply by ●November 18, 20212021-11-18
On 18/11/2021 01:18, 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?Default dumb USB chargers are typically 5v nominal at 1A or 2A current limited by the supply PSU. Anything beyond that and the client device has to negotiate with the charger to get either higher current or higher voltage or both. I have lost track of which combinations are allowed and accepted these days. I have various USB "fast" chargers in various Android and Apple flavours and some will do fast charge with certain devices and not with others. It is a bit suck it and see but the worst you are ever likely to see is a warning "device is charging slowly - use original lead and charger". -- Regards, Martin Brown
Reply by ●November 18, 20212021-11-18
On Thursday, 18 November 2021 at 09:14:08 UTC-8, Martin Brown wrote: ...> Default dumb USB chargers are typically 5v nominal at 1A or 2A current > limited by the supply PSU. > > Anything beyond that and the client device has to negotiate with the > charger to get either higher current or higher voltage or both. I have > lost track of which combinations are allowed and accepted these days. > > I have various USB "fast" chargers in various Android and Apple flavours > and some will do fast charge with certain devices and not with others. > It is a bit suck it and see but the worst you are ever likely to see is > a warning "device is charging slowly - use original lead and charger".... The usual approach is to use resistors on the D+ and D- lines at the charging end to signal to the device the capability of the charger. There is no negotiation. https://www.maximintegrated.com/en/design/technical-documents/tutorials/5/5801.html
Reply by ●November 18, 20212021-11-18
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. -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
Reply by ●November 18, 20212021-11-18
torsdag den 18. november 2021 kl. 18.06.37 UTC+1 skrev Ed Lee:> On Thursday, November 18, 2021 at 9:04:11 AM UTC-8, Carlos E.R. wrote: > > On 18/11/2021 16.51, Ed Lee wrote: > > > On Thursday, November 18, 2021 at 7:47:44 AM UTC-8, bobenge...@gmail.com wrote: > > >> On 11/17/2021 10:15 PM, Ed Lee wrote: > > >> > > >>> I am pumping 2A into a 2000mAhr cell at 4.3V when connected, and 3.8V open circuit. ... The only thing limiting my charging rate is the internal resistance. > > >>> ... > > >> > > >> How do you know that it's the internal resistance that's limiting the > > >> current and not internal charging circuitry? I think that you jumping > > >> to the simple/easy conclusion while the reality is much different. > > > > > > There is nothing else between my voltage source and cell. When connected, the voltage is at 4.3V, when separated, the cell voltage is at 3.8V. There is no other internal circuitry. > > Except that the cell itself can have circuitry. > No, they are bare cells. I opened up some just to be sure. > > If the cell cannot store more charges and turn them into heat, then by definition is the internal resistance. Most chargers avoid it by lowering the voltage or current, but doesn't mean the IR limitation is not there.USB "chargers" are not chargers, they are powersupplies, the charger is integrated in the device
