Ian Field wrote, on Mon, 30 Nov 2015 22:05:26 +0000:

If the one you tried melted the USB cable and overheated the appliance,
something is clearly wrong.

I think the cable was bad, because it's rare for a charger to
put out *more* than the 2.4Amps that it says a port can output.

But that doesn't help explain where the 40Watts comes from since
no calculation comes close, whether that's input RMS VA or output
Watts.