You can check the battery level in two different ways when the headset is powering on.
By LED Indicator
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%
By Voice Prompt Indicator
When you power on the headset, keep pressing the Center Button and the (+) Button simultaneously for 3 seconds until you hear three, high-toned 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 a voice prompt for the battery level indication.