You are using the Surefire charger? If so, how old is the charger? The newer models will have a pulsing blink when the battery is charged, if I remember right. Haven't used mine for awhile.
The older, non blinking chargers, it takes 12 hours. The newer chargers (rapid chargers) will blink, as bill said, and take about 2-hours. With the older one's, you CAN overcharge them.