Ive now been thru 2 cheapie adapters with a USB C plug for the phone and a USB C socket and 3.5mm socket on them so I can use the phone in the car for audio and charge it.

Both seem to limit the charge current to 500mA, plugged straight into my mi mix 2 I get 1.75A from the same charger (I have a USB C cable with a voltage/current display on it like an inbuilt charger doctor) 

Anyone had any luck finding one that does full current? Arriving with the phone with less battery than I left with is getting annoying, so much its driven me back to using bluetooth with the resulting terrible audio that my cars stereo has for that.