I Have the Samsung Galaxy S II, and use the built in GPS with an external GPS (via Bluetooth) that brings the heart rate signal to the Run.GPS Software, and after nearly 1 hour excersise, the battery drains only aprox 10% (depending how much battery you have when you beguin the excersise). I normally try to start with 100% battery.
Of course if you start with 50-60% battery, it will drain much more fast.
So in resume I have the GPS, BT active when excerisizin, and not much battery drains.
I haven't done any proper comparisons but using BT with an external GPS + Zephyr BT HRM drains the battery much slower than using the on board GS2 GPS. The external GPS is also much more accurate and holds the signal better under trees or around tall buildings.
Just an update. It appears that not being able to use an external GPS receiver is an Android restriction but after installing BlueGPS (free) you can use an external GPS receiver.
19.07.2011 12:21:45 UTCgeändert am 19.07.2011 12:22:32 UTC
Just using the trial version at the moment but it seems to work well. Tried to use an external GPS unit (Holux GPSlim 236) via bluetooth to save the phone's battery but couldn't get the Run.GPS app to see the gps signal even though it was paired ok. Had to resort to using the phones GPS which worked fine. I will investigate further about using the external GPS unit.