What happens if you use the Apple 29W USB-C Power Adapter to charge the LG G5?
Using software from Granite River Labs, we can see that the Apple 29W USB-C Power Adapter first offers 12 watts (5 volts @ 2.4 amps) and 29.6 watts (14.8 volts @ 2 amps).
The LG G5 then requests 5 volts @ 2.4 amps from the Apple 29W USB-C Power Adapter.
However, the actual current pulled by the LG G5 from the Apple 29W USB-C Power Adapter is only about 1 amp with the LG G5 when the battery is well depleted.
The LG G5 takes around 1 hour 35 minutes to charge completely while the phone is powered on state with the Apple 29W USB-C Power Adapter.