This USB Charger for the SKYLINER is all set to charge 2 batteries at a time, just in case you have spare batteries for that day long flying adventure. When the charger is plugged into a power source the charging light will remain off. When the SKYLINER Battery is installed, the charging light will come on with a solid Red light. When the Red Charging light goes out, indicating the battery is fully charged. Charging times are approximately 60 minutes, less the first charge out of the box.