On 02/01/2014 06:17 AM, Capt Rick wrote:
On Sat, 1 Feb 2014 07:08:11 +0000 (UTC), Danny D'Amico
wrote in part:


I plan on sacrificing a USB cable to that I can hook an
ammeter in series to test the actual current flowing.

No need to sacrifice a USB cable. Measure the current going into the
cigarette lighter adapter. Measure without the Galaxy plugged in for
any idle current. Plug in the Galaxy. Subtract idle current then
multiply by 2.52 for a rough figure - 12.6V / 5V = 2.52. For more
accuracy measure the actual 12V Voltage and the actual 5V Voltage of
the USB output.

The current will be less on the 12V end because it is a step down
circuit. Just for example, if 1A on the 12V side, 12.6V X 1A = 12.6
Watts / 5V X 2.52A = 12.6 Watts.

Rick

Don't know about modern vehicles, but I believe that with older ones if
the vehicle is running, the alternator puts the voltage at more like
13.6V, especially if it's still charging the battery after starting the
engine. Could be higher with a high-output alternator. They cut back
once the battery is charged, but there is that period of time where it's
higher.

TJ