Originally Posted by craftycoder
That is sort of exciting news to me. I didn't think I could convince myself to learn embedded programming and GPS design but if the phone can't stay charged with .5A coming with the GPS antenna running then I may have to. The first thing I'll do though is shut off the microwave triangulation stuff and see what the power draw is like. You can do this as well just by putting the phone in Airplane mode. At least where I ride I don't have any cell coverage anyway. My apps solution (if I can find one) will be more convenient than that.
I'm confused. If you're planning to use an external GPS receiver like the one you linked to on SparkFun, then the GPS receiver in the phone should be turned off, so that portion of the phone battery drain would be near zero. Maybe I'm misunderstanding what you're doing with the external hardware?
Another thing that's a bit strange is that the GPS receiver in the phone should not draw a lot of current. For example, the one you linked to from SparkFun only draws 0.043 amps while tracking. The one in the phone should be similar. The one I'm using in my own project draws only 0.033 amps. I'd be more curious about the power draw associated with the phone display. Displays suck power bigtime. Could it be that the big power draw is really the display, since it's ON all the time while you've got the GPS application on the display?