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.
models from LG and competitors did not have this restriction and worked with such devices.
However, it was one of concerns that battery consumption increases (more than four times faster than normal)
and device may power off due to a drained battery.
this case, the device operation may become unstable and product performance can also be affected.
Now new LG models do not support connection with high power consuming devices to secure stability of product use.