How do I charge the Wahoo Extended Battery? How do I know when it's fully charged?

There is a USB port for easy charging. To show the charge of the Wahoo Extended Battery there are four indicator LED lights. The light furthest to the left indicates that the battery is charging. The other three lights show the strength of the battery. If all three lights are lit then the Wahoo Extended Battery is fully charged and ready to give you up to 5 more hours of ride time.