I use no USB adapter. My sensors run with a CR3032 (3V) battery. Should last until one year, the manufacturer told me. I have these sensors since September and the charge is about 94% at the moment.
I’m using an Raspberry Pi 3 (integrated bluetooth) and the bluetooth binding (includes also blukii).
OH finds my built-in (bluetooth:bluez:hci0) bluetooth device. That’s the “bluetooth-gateway” to search for BLE-devices like the blukii ones.
I declared my blukii sensors in blukii.items, described here and then you can use them like any other item.