So if I have a 24v system then I could simply install that and get 64 watts out of the usb c port? Seeing you bucked your voltage up from 18 to 24 I assume you could do the same on a 12v system and get it to work? Would there be any draw backs to using a buck up converter on the 12v system? Like would the current wind up being super low and taking forever to charge? Or would it just pull more to get what it needs from the battery?
Like stated above, there are quite a few different "USB C" charging protocols (QC, PD, etc). If you just want a simple QC 2.0 charger for a 12 volt system, you could get something like this.
Amazon.com: PD Type C USB Car Charger Socket and QC 3.0 Quick Charger 12V/24V Car Power Outlet Waterproof Socket 64W Dual USB Charger Socket Power Delivery 36W for Motorcycle Marine Boat RV ATV (Type C+ QC3.0(G))
www.amazon.com
Just fuse it and hook it to the battery, no need for AC inversion. There is some debate on how much power you can actually pull from a 12 volt source, so it may not technically be "fast charging" but my phone registers it as a fast charge, and it takes a little over an hour to charge my phone from dead.
If you have a 12 volt system, I would suggest getting a 12 volt automotive socket.
Buy Female 12 Volt Cigarette Lighter Socket Car Automotive Marine ATV Truck RV Boats Lighter Socket Power Outlet Socket Receptacle, DAMAVO YM1084 12V/24V DC Flush Mount with Waterproof Plug (1 PC): Cigarette Lighters & Parts - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
Hook it up, and you could use any car charging accessory with ease.