Jeff Liebermann wrote:

On Thu, 16 Mar 2017 14:57:53 +0200, Micky
wrote:

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

I spent an hour on the Android phone with a friend, and because we
kept getting dicsonnected on whatsapp and also on Skype, the phone's
screen was on all the time, but I was plugged into a small cubicle
charger the whole time, and the phone charge stayed at 77% the whole
time.

Then the phone call ended, I closed the light, but left the phone on,
and let it finish charging for an hour. But after an hour or more,
it was still at 77%.

How can that be?

Later I was able to recharge the battery fully, use some and recharge
over and over up until now. Using a different cable. But if the
cable were bad, how to account for the first paragraph??

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:
http://www.ebay.com/itm/222262460143

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?

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