Battery would die quickly when unplugged, instantly if the phone locked.
Smooth repair thanks to the handy guides on ifixit. Took close to 45 minutes.
Pay attention when lifting the original battery from it's adhesive. You will need something with a thin edge, like the spudger provided, and must have a lot of patience. Slowly work away at the outer edges of the battery.
The battery is soft and is easy to puncture, trust me. It smells something like modelling glue when punctured and is caustic, again, trust me.