> instead of the 13.8v ports we currently have in cars.
That's a bit too much precision for that standard. It's only ~13.8 V when your car is running and the alternator is charging the battery. When the car is off, it'll be 13 V or slightly less.
And even when it's running, you have to expect up to at least 16V, some of the cars and trucks with larger alternators will run a bit higher, I've seen 15V myself but I've always heard that 16V is what to expect.
That's a bit too much precision for that standard. It's only ~13.8 V when your car is running and the alternator is charging the battery. When the car is off, it'll be 13 V or slightly less.