Force Band's LED will turn solid green when the band is fully charged. You may need to update your Force Band to see the green light.
Also note, that when your Force Band is low on battery and in need of a charge, it will blink red rapidly and eventually shut off. Simply plug it into a power source and wait for the LED to turn solid green. Force Band's minimum battery life on a full charge is 1 hour, but can last up to 6 depending on the mode you're using.