Standby (low power) mode only applies when the charge cycle is complete.
You can enable standby (low power) mode by clearing the Bluetooth® pairing list. This will remove all connected Bluetooth devices from the stored pairing list.
Press and hold the Bluetooth button for 10 seconds, until you hear "Bluetooth device list cleared"
In less than one minute, the unit will enter standby mode
Reactivate Bluetooth by pairing a Bluetooth source