I bought an iPhone 4 refurbished and had no problems with it for the first 6 months..... Then my phone would randomly turn off with 67% charge still in it. No apps were active, location services were off and WiFi was not on and yet the problem only worsened. If I wanted to use Safari to do a search or use my GPS, my phone literally had to be charging the whole time (or the dreaded white vertical lines of death would circle on my screen). Being a refurbished phone (and being out of warranty), AT&T told me it sounded like a bad battery and I could contact Apple to get one. Well, $79.99 before shipping didn't sound too good to me, so I found iFixit.com and bought the battery and appropriate tools for less than half the cost of just the battery if purchased from Apple.
The repair was super easy!! I watched MJ's YouTube video and found it extremely helpful. I tried skipping cleaning the metal contacts and had problems with my phone coming on and turning off over and over. LISTEN to the directions and clean all the contacts before closing up your phone. Once I went back and did that my phone has worked perfectly!!
I like how MJ tells you to turn the power off and to activate the vibrate button before removing the back panel. I'm not sure what this does, but I didn't see it in the photo directions. Thank you iFixit for your simple-to-follow directions and fair pricing!! I will definitely be a repeat customer and share my new-found awesomeness with my friends!!