On Fri, 31 Jan 2014 06:53:54 +0000, Danny D. wrote:

Does any of this make sense to you?

What's going on when GPS is enabled while the S3 is on the car charger is
just starting to make sense now, with respect to the current draw:
http://forums.androidcentral.com/sam...rger-us-2.html

The S3 uses the defined Micro USB charging standard.
If the charger or cable has the data lines shorted, the S3 thinks it is on an AC charger.
If the data lines are not shorted, the S3 thinks it is plugged into a USB port on a PC.
When the S3 thinks it is plugged into an AC charger, the S3 pulls a maximum current of about 800ma.
If the charger is LESS then 800ma. the phone may fall back to the lower current of a USB port.
When the S3 is plugged into a USB port (where the data lines are not shorted),
then the S3 pulls a miximum current of between 300ma and 400ma.
If the charger DOES have shorted data lines, but it can't handle the 800ma
AC charger setting, the phone falls back to the lower USB port rate of about 300ma.