For charging, the main LED is used as the indicator. With the USB power connected, the LED blinks to indicate the Sidekick is charging. During the charging process the LED sometimes comes on steadily for a few seconds then has a series of blinks. I've not so far managed to determine if there is an actual pattern to this. Ultimately, once fully charged the main LED comes on steadily at the low level and stays on as long as power is connected.