The UA Sport Wireless Heart Rate must be charged with a micro USB charger that is provided in the packaging. You will find the USB outlet located on the bottom left side of the inline microphone. There will be a small rubberized window that you can slide up and over to expose the outlet. After plugging in the headphones, you will see a solid red light appear at the bottom of the inline microphone. Once the headphones are fully charged, the red light will turn off. It typically takes less than 2 hours of charging time to receive the 5 full hours of audio playback.