You can check the battery level in two different ways when the
headset is powering on.
When the headset is powering on, the red LED flashes rapidly
indicating the battery level.
4 flashes = High, 70~100%
3 flashes = Medium, 30~70%
2 flashes = Low, 0~30%
Voice Prompt Indicator
When you power on the headset, keep pressing the Center Button
and the (+) Button simultaneously for several seconds until you
hear high tone triple beeps. Then you will hear a voice prompt
indicating the battery level. However, if you release the buttons as
soon as the headset turns on, you will not hear the voice prompt
giving the battery level indication.