aiya, dun let the blind leads the blind...those handphone sellers dun know anything one. Modern batteries are Lithium Ion, NOT Nickel metal hydribe.
The charger will definitely stopped charging after the manufacturer's recommended hours. The light is off, the batt is cold, how can it still be charging after that? Leave 12 hours for wat?????
us your blain..use your blain;p
that sounds unfortunate.
try removing the battery and using it on your camera. Does the battery meter show full charge? If yes, do try to use this battery heavily, and then see if the charging is normal from the second time onwards.
* if you find that after few hours charging, the red light doesn't go off, but the charge inside can sustain for few hundred shots, then it's not really a big deal. Don't get so worked up over a little red LED light