My Samsung S3 has been charging extremely slowly for awhile now. I can leave it plugged in overnight, and it will show only a 40-45% charge in the morning.
And I replaced the battery recently.
Searching online shows that many folks have resolved this by using a different USB cable — apparently the phone can sense if there’s any problem with a cable and will draw less if it thinks a cable is damaged.
If that doesn’t solve the problem, others say to try a new charger. I’ve got lots of USB chargers and cables around, so will try the different cable solution first, and if that doesn’t do anything, try a different charger.
UPDATE: An hour after I began writing this post, and, er, obviously before I posted it — my phone is apparently fully charged. The different cable, on first blush, appears to have solved the issue.