10 - 30 minuten
After over two years of battery use and charging, the original battery had used up its charge cycles and couldn't last half a day, let alone one. And I wasn't interested in getting a new phone so a new battery for about $30 seemed like the best deal to me.
Well due to my background as a professional model maker, I knew that I'd take my time with it regardless how easy it would be. I even took my time removing the back cover as it was still pretty tight on after the initial 2mm slide, just in case I snapped the glass panel. Removing the old battery and attaching the new one wasn't that difficult, I was only really careful when dealing with the loose part under one of the screws for the battery connector. Took me half an hour from start to finish, and the phone worked first time.
I took my time removing the old battery due to the adhesive being quite stubborn, I discovered the best way was to lever the plastic tool along the phones edge in multiple places using small amounts of pressure each time until the battery got loose enough. Also, when turning back on the phone, I noticed the phone couldn't find signal, but after a re-boot, the signal came back and the phone has been working like normal ever since.