Plz Help!!! Battery Problem !!!

I bought a new original samsung battery last week......... were the production date iz give as 20 feb 2013...............
The problem is when i charge ......... it takes a long time to charge 100%............
very slow in charging ................. it takes about 3 :30 hours to charge 75 to 80% .............
some one plz help!!!
sry fr my english