Can I use a mobile battery for the DDJ-200 to use it in places without outlets?

You can use a mobile battery when you connect your smartphone via Bluetooth.
Use a mobile battery which does not have a power-saving function*.
The mobile battery should be DC +5 V and 500 mA or more.
*If the mobile battery enters power-saving mode, the DDJ-200 may be powered down and the unit may not work.