Can a USB cable carry 12v?

Even with an appropriate boost regulator, the car charger can't supply enough power ([email protected], 10.5W) to charge the tablet ([email protected], 18W). I would look at getting a 12V buck/boost regulator you could plug directly into the socket with a 2A fuse.

Years have passed since this question was asked, and it is no longer true that you can not "get" 12V out of plain USB-2 or USB-3. I'm providing an updated answer because this question ranks authoritatively in Google, and I was looking for something.

Example cables that directly convert USB 5v power into 12V:

• https://www.amazon.com/DZS-Elec-Converter-Regulator-Charging/dp/B07121W7Q4
• https://www.adafruit.com/product/2190

Be advised, these cables currently only deliver about .7 amps (12v amps) which is about 9 watts. It's enough to power some small devices that expect 12V, but do not expect this to charge a tablet.

EDIT: I would suggest my approach if your only option were a "standard" 5V USB power supply. As @cybernard notes elsewhere, today we have other options such as USB-C (and has modes for up to 20V and 100 watts).

Actually years later USB type c now has a power delivery rating of 100w. This translates to 19v(or was it 20v) at 5A.

It should be easy to get that down to 12v with a simple resistor or converter.

You have to do your research carefully as many USB type C plugs don't offer the full 100w. So you have to shop around until you find one that does.