Scott Lurndal wrote, on Mon, 30 Nov 2015 17:38:04 +0000:

Q2: How does the device "know" to give tablets 2.4 Amps
(12 Watts) but a "mobile device" only 1Amp (5 Watts).

http://www.extremetech.com/computing...our-smartphone

Thanks for that article, titled:
How USB charging works, or how to avoid blowing up your smartphone

The article explained that USB 3.0 "cables" have 9 wires but when I
looked at the 6.8Amp charger, each USB slot seems to have only 4
gold pins on the white protruding tab. I presume the surrounding
metal is ground, so, that makes 5 electrical connections that I can
see in each USB slot of the 6.8Amp/40Watt "Smart" wall charger.

The article says there are three types of USB 3.0 ports:
1. Standard downstream port (900mA at 5VDC = 4.5Watts)
2. Charging downstream port (1.5A at 5VDC = 7.5Watts)
3. Dedicated charging port (1.5A at 5VDC = 7.5Watts)

The article did say "A regular USB 1.0 or 2.0 socket has four pins",
so, I wonder if they counted the ground shield because the sockets
on mine only have 4 gold strips on the white protruding tab, so,
I'm not sure which USB spec my sockets are.

While this is interesting, after reading that article, I didn't see
anything in there that explained the problem nor how to troubleshoot
it.