By default, the transmitter shows the connected device, volume level, and current battery levels of both the battery in the headset and the one in the charging slot. (pcmag.com)
Double - tapping the Power button will display the speaker's current battery level via the mood lighting. (tomsguide.com)
From the «Battery» section, you get information about current battery level, active connections and battery health status. (windowsphonearea.com)