10 - 30 minuten
I've had the iPhone 4s since launch day and my batter just started getting bad after my contract ended with AT&T. I didn't see the iPhone 5s as a big enough reason to sign another contract. So, I decided I would make my current phone last longer by replacing the battery. I would probably get a good hour with my phone before I needed to plug it it. It would drop 5-10% charge just from checking mail or sending a text message. I just couldn't live with it anymore.
The repair went well. I was a little worried that I broke something. After you take off the ribbon cable that attaches the battery to the board there was this little black piece that went under the screw that had a ring for where the screw goes in. I was able to put it back and get everything else installed correctly. The hardest part was getting the existing battery out. There was a lot of glue and I had the thought of me breaking my device quite a bit. Thankfully, it went really well and now my phone can go pretty much the whole day without a charge.
Use the right equipment. Get it from ifixit if you can. Take your time and be easy on the screws. The screws will strip if you abuse them. After you have the ribbon cable detached from the battery, just go for it and rip the battery out. It doesn't connect to anything else that you could damage by being rough with it. Do whatever you need to do to get that glue off.