Originally Posted by ww73
I think the big battery drain is actually the screen, more than the GPS (when in active mapping mode). Same thing happens when my kids play Angry Birds. In 2 hours my phone could be down to 20% battery.
Again, this is in my own experience, but I can have my phone in my dash cradle, plugged in and charging, playing MP3s through my car stereos aux input (not usb) and leave the screen on for 8+ hours and when I disconnect the phone, the battery is fully charged. If I do the exact same thing, but have google maps onscreen as well, the phone will die after a few hours and I have to let it charge back up for a bit before turning it back on. I'm sure it's not all just the GPS that's doing it, but having the screen and backlight on with the charger plugged in leaves the battery topped up, as soon as google maps (I'm hesitant to say "gps" only) is running, my phone starts draining faster than it can charge, assuming that it does continue to charge after starting google maps.
This is all just based on my own non-scientific observations. You statement of the phone draining quickly when the screen is on full time is absolutely true, but not my experience when it's plugged in and charging.