I replaced an iPhone 5s battery and avoided buying a new phone!
The battery would only hold a charge for a few hours. I thought, “Rats! I don’t like replacing a phone when it was otherwise perfectly meeting my needs.” Then I heard about Ifixit and the possibility of fixing it myself.
The guides were so detailed it made the process easy. Equally important was using the tools including the battery replacement kit, the phone opener and the magnetic mat to keep track of tiny parts.
The repair went well but I needed to open the phone more than once to retrace my steps when the repair initially failed. I found I had not completely reseated a battery cable. Once I found it and seated it snuggly to make a connection, it worked perfectly. So pay close attention to your connections. These are tiny devices! I’ve been using the phone about a week now and it is like brand new. Hurray, Thanks Ifixit, john