The Belkin USB-C Car Charger + Cable can charge the LG G5 but much slower than the LG G5 gets charged.
The LG G5 seems to have problems with a variety of USB Power Delivery based chargers (see problem with Anker and iVoler chargers) doesn't seem to properly as fast as it should with the Belkin charger as well.
Once I plug in the Belkin USB-C Car Charger + Cable into the LG G5, the LG G5 shows that it's charging but it takes a relatively long time before it can figure out how quickly it is charging.
In general, it takes up to 3 hours to fully charge the LG G5, much longer than the time it take for the LG G5 to charge using Qualcomm Quick Charge technology.
More analysis to come later on why the LG G5 isn't being charged quick enough by the Belkin USB-C Car Charger + Cable using USB Power Delivery.