I charged my n900 when the battery level is red and I charged it for around 3 hours already and yet it doesn't show battery full yet,it was weird because previously the charging will be completed after around 2 hours of charging but this time after 3 hours the yellow charging light is still blinking so I decided to turn off the wall charger and found out that the battery level were the same before I charge it, still low,so I take it for another charge and this time different things happened,again I turned off the wall charger after 2 hours and 30 minutes of charging the battery level is full this time but the yellow light keep blinking, why is this happening ?