Phone Battery stuck at 100% and keeps displaying charged when not plugged

[Salah Swilh]

I had a screen replacement for my phone and after it i plugged it to the charger while off and it kept turning on and off so i turned it on to see that it shows phone charged and at 100 percent. Then i removed it from the charger and it kept saying charged even after a while it was stuck at 100
...I installed twrp recovery and i think it shows the correct battery percentage because it discharges and charges normally
...i did a factory reset didn't help
...flashed it and it didn't work
...then i used its dialer to do a hardware test when i clicked on battery it showed (it was not plugged in ) :
Charging voltage 18 mv
Charging current about 500 ma
Battery voltage 0 mv
Battery current 0 ma

 

[Cougary]

I had same problem on my old S3 Neo but when battery stucks at 100%, it will last like 2 days with heavy use and then at one moment battery will start to drain really fast (100%-0% in like 45 minutes of normall use). After changing battery it was same. It is probably usb port or some electronic problem.