My iPhone's battery maximum capacity is at 78%

PS: Glad to have re-found this thread; have spent near an hour to research add'l details.

Then found item had been relocated and re-titled. I'd reported an earlier duplicate w/ SN.

And with 'live thread' gone, I've saved the text to re-post; but see you've offered reply now.

• Here's what was saved in my browser; may as well dump that here, to not let it go to waste:

"For some better idea(s) on Battery Health and perhaps service replacement,

see articles such as these:

• iPhone Battery and Performance - Apple Support

https://support.apple.com/en-us/HT208387

• Batteries - Maximizing Performance (iOS/Device Tips) - Apple

https://www.apple.com/batteries/maximizing-performance/#iosdevicestips

• iPhone - Official Apple Support

https://support.apple.com/iphone

• Repair Options - Apple Support

If product is under an Apple warranty, or not; contact an authorized

service AASP or an official Apple store/or service. You may be able

to arrange contact-less 'send-in' service; this could vary by location.

• Apple Repair and Repair Status Check - Official Apple Support

https://support.apple.com/repair

• Genius Bar Reservation and Apple Support Options - Apple

https://www.apple.com/retail/geniusbar/

If you have access to Wi-Fi network, that will use less battery power

than using Cellular network. This may conserve battery power longer.

Use 'dim' settings on display, this could help lower power usage.

Enable 'low-power mode' for longer runtimes on low power mode.

(Certain features will not work in low-power mode.)

When charging iPhone from portable computer, be certain computer

is plugged into the grid; otherwise it too may have battery issues.

• Apple - Find Locations stores/authorized resellers + repair service/support.

https://locate.apple.com/

The newer iOS has "Battery Health" display in settings; this also

shows a history of charging & usage, in second screen view.

My iPhone is small display early SE model; & not on latest iOS.

Would suspect your post could be relocated &/or edited.

Identifiers [serial numbers] should not be posted in ASC."

Good luck & happy trails!

🌞🌿⛵️🎣🌻🐢⛄️🌤🌎

Search online to locate and call contact your nearest, “local” Apple Store location to try/attempt to make an appointment to get your Apple Watch battery replaced.

OR, failing that,

Contact Apple support via the contact support link located at the upper right hand corner of every Webpage of these Apple support communities OR by installing and using the Apple Support app found in the iOS App Store.

Tap the iOS App Store link below.

https://apps.apple.com/us/app/apple-support/id1130498044

Best of Luck to You!