Basically, an electrical socket charger gives out about 1000 mA where a USB is around 500, so harnessing 2xusb ports theoreitcally can double it to the same as using an AC charger....

 

Found a link if anyone's interested.

Seems like a good idea. Shame they don't make one that switchable between data and charging. Otherwise its yet another cable in the rucksack.

Let us know how you get on.

 

With such a Y-cable double USB current (1000mA) is available.

But the phone will control its own charging, either slow charging with USB (500mA) or fast charging with double USB (1000mA).
And for to decide for fast charging the phone needs to "see" a coding in that Y-cable's microUSB connector.

So you'll have to know whether the Y-cable has such a coded microUSB connector

Harry