I've had my iPhone4 since it's release date and started to noticed that the battery wasn't holding the charge or at times, wasn't charging the phone after being plugged in overnight.
The repair was simple, thanks to the video guide on how to replace it. It only took me a total of 15 mins to switch out and replace. Although, I do recommend that you don't drink 4 shots of espresso in your coffee when replacing it. I struggled as my hands were shaking, trying to get the screw back in place, where the connection is.
HAHA...yes, don't drink too much caffeine. The screws are tiny.