iFixit:  If you’re worried you’re not getting the battery life you should, the battery may just be old. Over time, batteries degrade, leading to lower and lower life after a couple years—meaning you might be able to solve your problem with an inexpensive battery replacement. Apple rates iPhone batteries at 500 charge cycles, or about a year and a half of typical use–more on that in a bit. To check your iPhone’s battery health, you can go into the settings and navigate to Battery > Battery Health. If it’s under 80% or so, it may be time to replace the battery. We wrote a detailed step-by-step guide on how to check your battery health.

While you could take your phone to Apple for a replacement, they’ll charge you at least $50. You can save money by doing it yourself, and it’s much easier than you might think. We photographed straightforward and easy-to-follow guides for every iPhone model. We also sell the parts and tools you’ll need to get the job done for much less than Apple. But you’re nervous. Opening your phone is an endeavor. I feel you! But you’re not in this alone–we’ve got your back. And literally thousands of people have come before you. We get sent success stories every week from community members who’ve replaced their iPhone battery. You got this!…”