My LG G4 does not recognize an external HDD with USB OTG. Why?
If external HDDs or fans with USB connection is high power consuming,
they cannot be recognized when connected via OTG.
Note: If the momentary power consumption when connected via OTG is 600mA or greater,
connection will be lost.
How to fix
Standard USB rating is 500mA. Please note that devices are supported if their power consumption is higher.