Can a USB cable carry 12v?

Question

I have a Acer Iconia A500 tablet. I want to plug it in, in the car, but it has a barrel plug and I don't want to buy an inverter. The car adapters are expensive for what they do.

I already have a 2.1 amp USB car charger meant for the iPad: http://www.amazon.com/Kensington-K33497US-PowerBolt-Charger-Compatible/dp/tech-data/B003PU01M4/ref=de_a_smtd

I want to use this USB cable from the 2.1 amp port to plug into the A500: http://www.amazon.com/gp/product/B00304DZ7I/ref=ox_sc_act_title_2?ie=UTF8&m=A1HPBDJJIXKXS7

Here are the specs on the original wall charger if that helps: http://www.phihong.com/assets/pdf/PSA18R.pdf

The USB cable says it's 5v, but the original charger says it outputs 12v, and since it's just a cable, wasn't sure if that really made a whole lot of difference since it's only 1.5 amps from the wall charger.

Is it possible to use that USB cable through the powerbolt car charger, to charge the A500?

Answer 1

Even with an appropriate boost regulator, the car charger can't supply enough power (5V@2.1A, 10.5W) to charge the tablet (12V@1.5A, 18W). I would look at getting a 12V buck/boost regulator you could plug directly into the socket with a 2A fuse.

Answer 2

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).

Answer 3

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.

Answer 4

The PowerBolt charger is a 5V source, since it's designed for USB devices. It'll still be a 5V source even if you plug your tablet into it. That probably won't be enough to operate or charge the tablet, though I doubt it'll cause damage. (But I don't know enough about your tablet, or electronics in general, to say for sure that it won't cause damage.)

Make sure the polarity of the barrel plug on that USB cable matches the polarity of the tablet's original charger. Getting the polarity reversed can potentially damage the tablet.