heddy

I had to make an account to point out that the author is horribly incorrect here. It's a known fact that charging lithium-ion batteries to 80 or 90 percent is massively beneficial for the battery (Source: Battery University, Apple, every electric car manufacturer, every battery engineer). The highest non-damaging voltage for lithium-ion is around 3.96 volts, but charging to 100% results in 4.4 volts for the typical Apple battery, which damages the battery health fast and drives people to replace phones fast, which is very wasteful. Lower max charge level = lower max voltage = longer lifespan, and better performance during the lifespan. Higher voltages are exponentially more damaging, so even a small reduction in max charge level can have massive benefits.

If you truly need every single percent, then sure, don't use this setting, because this setting isn't for you. But for many people, this setting is amazing. We can use this setting for most days, thus preserving the battery health, then we can turn off this setting and charge to 100% for when we truly need the full capability, like a vacation or trip where we won't have access to charging. And that way, 100% will actually be 100% because the battery won't be as damaged as it would be if we had charged it to 100% every single day.

If preserving battery health, less need for battery replacements, and the battery working amazingly on the few days the full battery is actually needed doesn't sound great to you... then this is not for you! But don't spread uninformed messages like "oh this is useless... oh this is confusing... oh this only adds a few weeks of lifespan." It has a clear and easy to understand purpose. The lower your max charge level, the exponentially longer the battery lifespan. Even capping the charge at 90% for your non-busy days and un-capping back to 100% on busy days will have a great impact on battery health. If you charge to 100% every day, you are not actually getting 100% capacity because your battery will be so damaged it will start losing capacity in a matter of weeks of use. Meanwhile, people who use the cap will stay at 100% battery health for quite a while, and when their battery health starts to drop, it will drop very slowly!

In addition to what engineers say, I know from personal experience that a lower charge cap adds years of useful life. Years, not weeks. My 3-year-old iPhone is at 96% battery health, whereas it would surely be at 70% health or worse if I had charged it to 100% every single day. I used an automated notification, to alert me of charge level 80% or 90% being reached so I could pull the plug when I wanted. Apple adding a setting is a huge improvement, because I will no longer need the alert or manually stopping the charge. There's a reason Apple adds this setting... it's because their engineers know it works. I'm sure Apple would love for people to keep charging to 100% every single day to increase sales of replacement batteries, so I applaud Apple for adding this setting.

A different setting - the "optimization" setting that reduces the time the battery spends at 100% by charging right before you wake up - is good for batteries because it reduces time spent at the highly damaging 4.4 volts. Of course, not spending any time at that voltage is even better, so I truly appreciate Apple for adding the option to cap the charge level.

Fact: the lithium-ion industry standard max voltage is 4.2 volts, and the nominal voltage is 3.7 volts. And yet Apple and the entire smartphone industry pushed the max voltage to 4.4 volts and pushed the nominal voltage to 3.8 volts. Apple's engineers say they used better materials to support the increased voltage, but materials can only do so much... Apple's (and all smartphone makers, to be fair) use of higher-than-industry-standard voltages are one reason why their batteries only perform well for 1 to 2 years, when previously lithium-ion batteries would perform well for 3 to 7 years.