The battery is attached to the back plate of the iPhone using adhesives you know? Glue. Soldering isn't even an option considering the back plate of a 3GS is plastic. For future reference, removing a screen (both digitizer and LCD.) while on will have no effect. You just can't use the iPhone (duh). Though, you can flick the switch on top of the volume buttons that make the iPhone go *vroom vroom* on and it will work.