iOS 18 Actively Recommends Charging Limit Based on iPhone 15 Usage

I charge my phone overnight, to 100%, every day ... don't care about battery health/lifespan. Its a consumable, when it doesn't meet my needs anymore it gets replaced

They’re getting to a point where people can hold onto their iPhones for 10 years. If I’m a shareholder, I’m asking what Tim is doing to replace the lost revenue from iPhone users who aren’t upgrading?

Replacing it with services revenue.

what are we saving by never charging above 80%?

You're reducing the accumulation/creation of dendrites.



Dendrites are crystal-like formations in the cell that grow through the electrolyte, little by little, with each charge and discharge cycle. They cause short-circuit in a cell when they grow all the way through. This is the main way a li-ion cell dies.

Dendrites are formed primarily during deep charging and deep discharging. E.g., when you discharge the battery down to 0%, and when you charge the battery up to 100%. If you stay within the 20%-80% charge range all the time, a modern lithium ion cell can last probably 10x as many cycles compared to a battery that is cycled between 0% and 100%. But staying in that narrow range sacrifices 40% of the battery capacity, so it's pretty undesirable. Indeed, everything about battery design is balancing competing interests and picking 2 of 3 options.

Most battery controllers don't let you go to 0% anyway. When your phone is reporting 0%, it likely really means the battery has 1-3% left but for self-preservation it's not going to let the device turn on in that state. And most folks don't discharge their phone all the way daily anyway - it's a rare occurrence to be plugging in a totally dead phone. But most battery controllers let the battery charge to 100%. So dendrites slowly form.

By limiting the charging to 80%, you're greatly reducing/slowing the formation of dendrites.

But 80% is a bit aggressive in my opinion. Dendrite formation becomes a real problem at the extremes. 90-95% charge limit would be fine I think.

This is looking more and more like something in the hardware of the iPhone 15 models that allows the charging limits as well as this new feature. Maybe something controlling the USB C port or the battery controller itself?

All existing devices since iPhone 6S can do Optimized Battery Charging, which delays charging past 80%. All iPhones can pause charging when high temps are experienced. So we already know existing hardware is capable. This is confirmed by the fact jailbreaking can re-enable this artificially locked feature on iPhone 14 and older. This is a case of pure feature rationing.

For iPhone 12 mini users: “Based on your iPhone habits, a charge limit of 150% is recommended.”

Apple has gone from not allowing this at all, to actively pushing the feature in the span of two years.

I wonder what caused their change of heart?