I have a standard stock battery in my Fascinate and it will last a couple days if I have the GPS and WiFi turned off. If I use the WiFi, the battery will last 8 hours max; If I use the GPS, I'm lucky to get 4 hours. It doesn't seem to matter which apps are running or if I'm talking a lot. I did get a 1500 mah battery from EBAY and it's great. I use it when I'm away from home and using the GPS mapping and nav services, and it will last a couple days. It came with a new back case for the Fantasy, because it's twice as thick as the standard battery, so I don't use it most days.