My phone battery was the electrical equivalent to playing Russian Roulette. If the battery percentage was below 70%, it could shut off at any moment. 60% battery you say? Surprise, it's now 20, and 5, and phone is off. I never knew if googling which fish to pickle, while at the fish counter at the grocery store, was the last thing I'd be able to do before complete and total darkness, or if the phone would last through another thirty pointless text messages and an unnecessary snap (without filters).
The repair was easy until I had to pull the adhesive off. There should be a warning about doing this carefully, and what angles to pull from. Needless to say, both pieces of adhesive tore off. So I cursed the phone and took out my swiss army knife and etched under the battery hoping to pop the thing off. Unrelated, two interesting facts about these li-ion batteries: 1) they bend, like 30 degrees at least 2) there doesn't seem to be liquid inside. Needless to say, I have a bent and torn li-ion battery on my desk. Pretty sure that's not safe.
Jokes aside, it was relatively easy, though I was worried about not getting the battery out. Carefully etched it out, replaced it, clicked the parts back in place, and voila, my phone doesn't die instantly anymore. Feels great.
Be careful with the battery adhesive. That $@$* just wants to tear off. But in the event that it does tear off, you can wedge a very thin sturdy piece of metal under it, and bend the battery out. And if you do that, don't blame me if it explodes or whatever dangerous thing could happen.