i've got same situation "maybe"..
but my s3 mini can use normally but except charge the phone...
phone cant charging up battery, just icon appear but not up percentage of charge..
and usb not detected..
i dont know exactly the prob of mine..
maybe "i've rooted and install Rom and restore Stock Rom" and tried to change some icon in Stock Rom..
and its start the problem with when charging up to 99% suddenly drop down one by one percentage battery..
and send to samsung warranty, they send me back the phone since my phone is rooted "i assume", haha.. they didn't tell me y not repaired....
so solution :
install back Custom Rom, and restore back stock rom ( fortunately i've got backups )
and tried to charging and tried usb to pc, it works normally...
i thought port usb and charging damage and nearly want sent to shop to repair.. haha