Bettery Health

Same problem here! I’m guessing you updated to iOS 16? My iPhone 13 Pro Max, got it brand new directly from Apple when it first came out, was 100% then 99% battery health. After updating to iOS 16 boom! 98% then a few days later, 97% then today it’s 96%. So basically 1% every week or so.

At this rate I’ll need a new battery every 20 weeks or so!

On average, battery health declines about 1% a month. However, that decline is not always linear. Battery health may stay the same for a couple of months, then drop by a couple of points. Also, battery health is re-calibrated when a system update is done so, if you recently updated to iOS 16, that could have caused the number to be recalculated.

How old is your phone? What is your battery's maximum capacity?

There is nothing magical about only charging your battery once a day. You can charge it as often as you want. See here for more information:

When to charge your iPhone or iPad - Apple Community

That is a little more decline than most people see in that time period, though not completely unheard of. I would suggest that you contact Apple and arrange for them to do a diagnostic. They can do some of them remotely.

Genius Bar Reservation and Apple Support Options - Apple

Same thing happened with my device

putri03 Said:

"Bettery Health: Why can my battery health decrease 2% in one week with normal usage (never use until overheated, screen time around 4-6 hours per day, charge once a day)??"

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About Battery Health:

Unfortunately, there is no way to determine why, nor when, a Battery Health percentage decreased. It may be a bug in a recent update.