On Sat, 01 Feb 2014 05:17:38 -0600, Capt Rick wrote:

No need to sacrifice a USB cable.
Measure the current going into the
cigarette lighter adapter.

Now why hadn't I thought of that!

I can just hook an ammeter across the fuse
for the cigarette lighter socket, which
will give me the current being consumed
with, and without the phone being charged!