How can it keep charged in use, but be unable to recharge?

Any chance one of those apps didn't really shut down due to a bug? Or maybe the charge indicator is (was) out of calibration. Or maybe something was sensed as too hot (the battery? the charger?) and didn't work until it cooled down. Just wild guesses.

Pat

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Whenever I have state-of-the-art questions about computer software/hardware, I try to visit the PC Gaming or PC Magazine websites.

Could be a quirk of the battery controller in your phone. Or perhaps the 'small cubicle charger' (whatever that is) could supply sufficient current to keep the phone going, but not enough voltage to bring the battery to a full charge. I think a long thin cable might have enough resistance to have that effect, or one with a damaged conductor.

Since the phone was on continuously, probably with full backlighting, and apparently while talking, it was drawing quite a bit of current from the battery. If your "small cubicle charger" was a gutless clone charger, that can only supply perhaps 0.5A at 5V to the charge controller in the phone, you could have been breaking even. If the total draw equals the charge current, then the phone is running off the charger, not the battery, and the battery SoC (state of charge) remains unchanged. You'll need to supply some more numbers to verify this. One of these will help with the charger part of the puzzle:

However, you may have had a different problem. The constant 77% indication suggests that whatever is delivering this number (OS or some app) is hung. Since it recovered later, did you reboot the phone?

On top of what has been said, some chargers simply refuse to recharge when the battery is not low enough. Look at laptops, if you don't USE the batter y the thing will stop recharging period. Some of them you have to take the battery out and unplug them to get them to charge again if you do not use t he battery.

If the circuitry reads the battery as charged "enough" it may well refuse t o charge. It depends on the make and model and type of battery.

Some of them you cannot just "top off" like an old car battery in a 1967 Ch evy. They actually require cycling to work properly. So even if it causes y ou an inconvenience by dying a bit son, the point of the circuitry is to pr eserve the battery.

The technology is much better than it used to be but is still not perfect, especially when you require amp/hours out of a battery thinner than your cr edit card. Also, overcharging low quality batteries has been know to cause them to explode.

So when something like this happens, disconnect everythng, and if you canno t take the battery out, make sure to run it down. Watch ten movies on it or whatever, unplugged. Run it down to like 40 % and I bet it will charge. If not, there might be something wrong with it. (or the charger of course)

How old is the battery? Maybe it never gets above 77% until you get a new battery.

Yes.

Yes.

Yes.

I may have turned it off. It charges faster when off, though one friend of mine told me it only charges when on! Huh? I'm sure mine isn't different from his.

It doesn't charge very fast when on, even when the screen is black. But I know the lit screen runs the battery down far faster than with an unlit screen. So if the charger can keep pace when the screen is lit, why doesn't it charge faster when the screen is unlit.

Maybe Whiskers is right. The voltage of the charger is exactly or very close to the voltage of the battery, so the charger can also run the phone but it can't charge the battery.

How do those rechargers work, the size of a cigarette pack or so that charge when there is no outlet? Do they use a different battery that puts out more voltage**, or do they just even out the charge, like if you have an empty glass and a full glass, and you pour half a glass into the empty one? **If the charger put out more voltage it would take that much longer to recharge, and would never recharge from the little cube (maybe not cubicle) charger I brought and my friend also lent me. (I brought a bigger one too, that came with the phone, but mostly I'm using the laptop port..)

The battery was new with the phone last June or July, but as I said, later I fully charged it, to 100%. And I have done that at least 10 times since. Using a different cable.

Well, there's an easy way to find out. Buy one of the various USB ammeters and measure what the charger is doing. So, I tried it. I turned off my Samsung S6 phone and plugged in the stock Samsung 2amp charger. The screen showed a gray battery symbol with an ominous lightning bolt in the middle, which I assume means that it's either charging or self destructing. The gray battery symbol then filled up to 100% because the phone was already fully charged. The screen then announced that "This phone is capable of wireless charging". It would appear that the S6 is capable of charging when turned off.

What is "it"? Maker and model please. If you plug a 0.5A or 1A charge into a phone that was designed to use a 2A charger, it will take much longer to charge.

It does charge faster with the screen off. If the charger is delivering 0.5Amps, and the screen is drawing 0.4Amps, then the battery is only getting 0.1Amps.

The LiIon external "I forgot to charge my phone" devices have one or more LiIon cells inside. Depending on the number of cells and feature list, a DC to DC inverter produces 5.0VDC at the USB connector. Circuitry on the PCB also take care of charging the LiIon batteries from a USB 5.0VDC charger. The voltage is always 5.0VDC.

To the phone, these devices look like a 1A or 2A USB charger. They supply 5.0VDC to the phone. The charge controller inside the phone decides how much current to suck out of the device, which is then used to charge the phone battery or run the phone.

I have a bunch of these that I inherited from various disreputable sources. They work well at moderating my erratic charging habits. None of them even come close to their advertised capacity (in mA-hrs).

I bought a bag of very thin USB to microUSB cables (in 10 assorted colors) on eBay to give to friends as holiday bribes. No problems or complaints yet. At the low price of these cables, if you suspect a problem, just replace it or try a heavier cable.

Of all the answers you've received this far, none proposes as candidate explanation what I'm about to suggest, which is: the phone's charge circuitry simply failed accurately to detect the new state the phone entered once the call ended, the charging function simply stopped, and the charge level never increased beyond the 77% you saw.

Once you turned the phone off and on again (or hibernated and reawakened it), the state change became more obvious, and charging proceeded normally, recharging fully.

I've encountered similar "losing track of the phone's state" events with an old WinMo Motorola handset (a Q9m). Switching the phone off and on again resets everything back to normal. Kinda like "stty sane" in Unix/Linux :-).

HTH, though YMMV. Cheers, -- tlvp

charge in use

and

charge not in use

are 2 separate circuits

SUI

ahhhhhhhhh next week's allowance

whattsa booyalvong ? Utahspeak ?