I saw that this option exists. Is it advised to charge not to 100% if it is not necessary to get through the day?
It’s an option. I’ve been trying to rarely charge my iPhone 11 to 100% and never discharge it fully since new. And Battery Health still shows it at 93% capacity.
But while I question Apple’s Battery Health feature, see Oct 2023 post below, my iPhone still easily gets me through the day and normally goes 24+ hours on standby. So I have my M2 iPad Air set to charge to 80%.
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For what it’s worth, I have “Optimized battery charging” turned on which is basically “smart” charge to 100% and in one year my battery health is at 98%
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I do and my battery on my 15 pro is still 100%.
I’ve found I really don’t need it to 100% a majority of the time and when I do I have an anker magsafe charger handy.
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I’m also charging to 80% on my 15 Pro Max with the same results, and typically have plenty of capacity for day to day use.
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I don’t agree with Gruber’s conclusion, 4% saving in a year is a lot.
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I agree that 4% is a lot, but I am not so sure that you absolutely have to enable the 80% option to prevent battery degradation. I think it depends on how you are charging your phone: how often, when and under what circumstances (temperature, duration).
I posted about the battery of my iPhone 15 Pro Max 5 days ago:
Apple apparently is doing a very good job preserving your battery with the standard setting for optimized battery charging, if the iPhone is able to reliably predict when and how you are charging and picking up the phone. My way of charging three hours on a Belkin Wireless charger from 3:30 to 6:30 am (the charger is receiving power only during that period from a smart plug) has the result that the iPhone starts charging at 3:30 and until it reaches a healthy charge level of 80%. And finally it pushes the battery to 100% not much before 6:30 am. My result: each day an iPhone fully charged at 100% with a battery capacity of 100% after one year. I am impressed.
I have no CarPlay, so my iPhone is not charging in the car and I do not charge it apart from this nightly session. My phone is sitting on a stand in the office by day - with no wireless or wired charging connection.
The 80% setting may be a good idea, especially if the iPhone is connected to a charger very often (wired CarPlay connection, stand with a built-in charger and so on). But if not… I don’t know. It is nice to have the actual capacity available if you need it. Unexpected things can happen. A few years ago, I had a little accident and had to go to the hospital. I was so glad that my iPhone was fully charged back then: when I woke up from the surgery at about 3 am, my iPhone still had about 30% charge and it was only in the morning when I was able to get it charged again (when I was able to get hold of a charger again).
EDIT:
I think, this user has a point (Macrumors forum):
The more damaging part is keeping the device at 100% for longer periods of time. Charging it once and then using it is less harmful than keeping it at 100% overnight. (…) But aside from 100% charging, draining it to 0-20% also does harm.
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Someone reporting their Coconut Battery stats can be misleading, as their exact pattern usage in terms of apps, charging time predictability, may not be same as ours. Or simply the battery was a lemon.
The scenario was certainly the case with older batteries in the days of Macbook Core Duos but I’d say that battery technology has changed quite a lot in the last decade. I simply just trust what Apple does with their energy management. My iPhone 8+ was asking for a replacement battery after 6 years or so but it still was useable so I think it’s fair to say that Apple knows their stuff. I see that iOS 18 allows to adjust the maximum battery charging level, so if the option is there I would use it, no questions asked.
I was more referring to the general stuff mentioned in that post (as quoted). Batteries do not like to be kept drained (running the iPhone down to 10% daily may not be ideal, either) or at high levels for a long time. My iPhone 15 Pro Max still has a max capacity of 100% after one year. With just the normal settings (optimized charging, no fixed level of 80%, daily charging for three hours, at always the exact same times - Apple is able to do its job preserving my battery’s health under those circumstances, without the 80% limit). And I get to use the full battery’s capacity if needed.
I think, Gruber has a point when he is saying: “(…) there’s no practical point to limiting your iPhone’s charging capacity. All you’re doing is preventing yourself from ever enjoying a 100-percent-capacity battery. Let the device manage its own battery. Apple has put a lot of engineering into making that really smart.” This is exactly what I have experienced and that is the point I was trying to make.
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I still need to gather some experiences with the battery life of my new phone (e. g. not plugging it in as soon as I see a charger and not panicking if I see it’s not in the yellow save mode 
). But it looks as if 80% is a bit too little for me. I work in an area with bad mobile network and this always drains the battery a lot. I feel better with more capacity when leaving in the morning. But I got kind of nervous with my old phone, I probably shouldn’t worry too much when only on 40% in the afternoon.
Anyway, I also come to think that Apples auto-mode should probably give the best results.
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This is the crux of Lithium Ion batteries. Too much time at either end of the scale is what leads to degradation, I’m guessing that Apple understands the quality of the batteries they provide and believe 80% to be a good cut off point unless you need more usage between charges.
96% health v 88% health in a year is a 66% delta (4% battery health loss Vs 12% battery health loss) , it’s massive. For someone keeping their phone for 3 years + it makes such a significant difference.
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Also noting that the cost of a battery problem due to charging issues isn’t “replace a $1000 phone.” It’s “spend $100 on an out-of-warranty replacement battery.” And if you pay for monthly AppleCare, as long as you’re paying, the replacement battery is covered.
Obviously you don’t want to do that any more than you have to, but I think it puts the whole situation in some perspective. 
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After some years (5?) battery replacements may not be available either from Apple or official services, and 3d party aftermarket replacements will have worse performance. But by that time I’d say the device is more or less amortised and you can use the cheaper batteries to extend the life of the device until the new shiny iPhones are released.
I agree. Gruber gets a new iPhone every year, so he could care less. And by the end of that one year even he is only enjoying an 89-percent-capacity battery.
there’s no practical point to limiting your iPhone’s charging capacity… Let the device manage its own battery. Apple has put a lot of engineering into making that really smart.
If there was no practical point in it and “optimized battery charging” was adequate, I doubt Apple would have added the 80% limit as an option.
All you’re doing is preventing yourself from ever enjoying a 100-percent-capacity battery.
No, I can turn off the 80% limit any time I expect to need full capacity. (And it automatically charges to 100% occasionally to maintain calibration.) But most of the time 80% gets me through the day.
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It somewhat depends on how you use the phone.
If you tend to use it until the battery is red and then charge it so you can use it more, you’re going to benefit the most from 80% limit because you’ll be prevented from taking it from 100% to near zero hundreds of times. It’s a bit of behavior modification to protect your battery (and make you take more breaks.)
If your usage is steadier, it probably fits in an 80% band and so it doesn’t matter much if you go from 100 to 20 or 80 to 0. Probably not a lot of gaming or other battery-burning activities.
(Then there are people who truly need that full battery range most days, due to their job or whatever. It’s worth it for them to wear out their batteries faster in exchange for that utility.)
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I’m glad that works for you, but very few people are ever going to use a hack like that to work around the fact that Optimized Battery Charging is worthless if you don’t always go to bed and get up at the same time.
I find the 80% limit much more convenient. I throw it on a charger and connect it to CarPlay whenever I want, and the battery capacity of my 15 Pro Max is still at 100%.
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Isn’t that nice? There are so many ways to achieve what we like to have! 
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Or they can get one of those batteries that snap onto the back of an iPhone and charge it via MagSafe. That’s what I’d do.
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That’s an interesting point. I know people who regularly leave their devices plugged in for hours after they’re fully charged and frequently run them down to single digits or even zero. I so habitually avoid running down that low that I rarely think about it.
My 5 year old 11 pro has 85% capacity with “optimized battery charging” enabled, but I don’t recall if that option has been available the entire time I’ve had the phone. At any rate, I’ve always put my phone on the charger in the evening & taken it off in the morning and have been lucky to never experience any battery drain issues.