iPhones are typically rated for 10 to 12-hours of battery life. That includes the new iPhone X, iPhone 8, or iPhone 8 Plus, or the still-for-sale iPhone 7 and iPhone 7 Plus, iPhone 6s or iPhone 6s Plus, or iPhone SE. If you've updated to iOS 11.3, or you're upgrading to a new iPhone, you might see a serious drain on your battery life. Here's what to do about it!
Whether you restore from backup or set up as new, your new iPhone or updated version of iOS 11 could expend up a lot of power downloading apps, games, mail, photos, and other content. That's because the Wi-Fi radio stays on for a long time, and Spotlight — the iOS search system — has to index everything. Some apps rebuild their own libraries and databases as well. When radios and processors can't sleep, power consumption goes way up.
If you've just upgraded to a new iPhone 8 or iPhone X, updated to iOS 11, or restored, give things a day or so to finish up and go back to normal. If you're fine after that, great. If not, keep reading!
Test on standby
In addition to the system taking a while to really finish transferring everything over, we also tend to spend a long time playing with new phones and new features. That's especially true with things like Animoji, Portrait Lighting, and Augmented Reality (AR) apps. So the screen stays on, storage gets written to, WI-Fi and maybe cellular radios stay lit up, and power gets consumed.
In other words, if you're battery feels like it's only lasting half as long, the first step to fixing it is figuring out if you're using it twice as much.
So, note down how much battery life you have left. Then put your iPhone down for 20-40 minutes. When you pick it back up, note down how much battery life you have left again. If there isn't a big change while in standby, you're probably okay, and your battery life will return to normal when your usage returns to normal (after the novelty wears off).
If your iPhone continued to drain and drain fast, even when you weren't using it, keep reading!
Rebooting, restarting, or resetting is the oldest cliche in troubleshooting. Because it works. Sometimes a good reset is all that's needed to kick bad bits loose.
iPhone X and iPhone 8 require different button combos than previous iPhones:
Quickly click and release the Volume Up button.
Quickly click and release the Volume Down button.
Press and hold the Side button (sleep/wake, on/off).