I have an iPhone 5 that is about 18 months old, so I am not yet eligible for an upgrade. This is a bit of a problem, since my phone's battery has lost the ability to hold a full day's charge. I did this to myself. I tried the Moves app. It is a step counter and gps application. It can tell the difference between walking, running, and cycling. It runs in the background and on an iPhone 5 it drains the battery. After six months I could see that the battery was being affected.
I deleted the app, but it appears that the damage has been done. It became hard to make it through the day on a single charge. There was a recent trip, where I had a boarding pass on my phone, but I had to get a printed boarding pass isnce I was not sure the phone would last until I boarded.
I bought a new battery and the tools needed to install it from Ifixit.com. The video and written directions were pretty clear. You have to remove the screen with a suction cup and be careful not to pull the screen completely off until some delicate ribbon cables are detached. The screws are very small, but the provided screw driver worked well. The hardest thing was putting the screws back in. They are very small, and if they are not placed perfectly they can pop out of the holes when pressure is applied. After many attempts I got all of the screws in and reattached the screen.
I turned the phone on and nothing happened. I feared that I had done something wrong, but I continued to try it and eventually the phone showed the dead battery screen. Apparently the battery was not charged. I had not expected that. After a full charging, it worked great. I have comfortably making it through a whole since I changed the battery.