GPS plus active maps that use data, yeah, that will use a LOT of battery. I have the Navigon app on my iPhone, and it basically costs me almost 1% for each minute I use it. I have a 50 minute drive home from work, and if I start up the app, it will eat about 45% of my battery. Navigation apps chew through batteries like a fat guy in a cake eating contest.
Which makes my handheld GPS units all the more impressive for their battery lives. I've tested both of them with brand-new AA batteries (each unit uses 2 of them) turned on and sitting on a windowsill where they can get satellite reception. My DeLorme Earthmate PN40 runs for about 12 hours, and my Garmin eTrex Legend HCx runs for about 24 hours! The PN40 has faster dual processors and satellite imagery (saved onboard, but still needs to render), so that's why it doesn't last as long as he Legend. Of course, if I had a small single battery like a cell phone, it wouldn't last as long either. Currently, I'm running 2700 mAh rechargables in both of them, so so that's a total of 5400 mAh, WAY more than the 1300 mAh battery in the Inc.
