The factor that contributes to battery wear is full charge discharge cycles. It’s a fact of the chemistry of the battery. You’ll notice that most devices arrive out of the box charged to about 50%, which is the most chemically stable level for the battery.
Keeping the charge as close as possible to 50% (max 80% and min 20%) will likely make your battery last longer, but by how much is debatable.
If I were a manufacturer I would kill the percentage display, limit the charge to 80% but display it as full and display a 20% charge as empty. But if I did that, I suppose I would reduce profits from battery replacement and device upgrades!
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A post was split to a new topic: MacBook Pro battery setting that limits charge to 80% not working
I presume Apple has collected more than enough telemetry from our devices to publish a comprehensive paper on the subject. It would be a delightful project for a competent statistician.
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If only it would be that simple. Modern Lithium rechargeable batteries are affected by several factors, including:
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Age. Even if it has been sitting disconnected since manufacture, it will lose capacity over time. After 2-3 years, the loss will be significant.
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Charge cycles. As you wrote, this is a big deal. Modern batteries claim to support more cycles than ones designed a decade ago, but all will lose capacity as they experience more drain/charge cycles.
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Temperature. If it gets too hot, lifespan will be reduced. Not just obvious things like leaving a phone on a car’s dashboard in summer, but also the heat of a CPU running at capacity (e.g. a long gaming session) or a display driven to high brightness (e.g. outdoors on a sunny day) will likely have an impact.
Fast charging can also create heat. But generally not enough to cause overheating unless the device is trying to fast-charge a battery that is close to full.
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Deep discharge. If a Lithium battery drains all the way to nothing, it will be impossible to recharge it. Protection circuitry will prevent it from draining that low - the circuitry will power-off your phone when the batter gets low enough for this to be a concern, but if it drains to shutdown and you don’t charge it soon afterward, the natural self-discharge rate may reduce it down to the point that the protection circuitry will prevent all charging - to avoid the risk of fire from trying to charge a battery that can’t be charged.
But even if the level doesn’t drop below the “no charge” threshold, running low on a regular basis can shorten overall capacity.
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Charging to 100% all the time. Many claim that merely allowing it to charge to 100%, even at slow rates that don’t cause overheating, is bad. I’m not convinced about this one. If it has an impact, I think it’s going to be less than the items I mentioned above.
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Storage when fully-charged or drained. The recommendation is that a battery should be at around 80% when disconnected for long-term storage in order to maximize shelf life. Too low may result in self-discharge below the “no-charge” point if it remains in storage for too long. Others here have written about a chemical reason why storage at 100% is bad, but I don’t really understand that part.
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Great post, but I’ll note that Apple recommends long-term storage at about half-charge - as close to 50% as you can.
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I won’t try to argue here, but note that Apple is talking about storing a device. The 80% figure I heard is meant for when a battery is disconnected from any device. For example, when a manufacturer ships batteries to a factory for assembly or if you have an (older) device with removable batteries, and you remove it from the device for storage.
I assume that there is a difference between the two situations.
I’ve now owned the 15 Pro for a full year. 97% maximum capacity, 244 charge cycles. The first five months I did strictly USB-C Power Delivery charging (with two times using a MagSafe battery pack), but in the last seven months I have done exclusively 12 watt USB-A to USB-C charing, as most of my charging is done overnight (and occasionally in the car).
After one year my 13 Pro was still at 100% maximum capacity, but I have no idea what the charge cycles were. (Probably very similar.) At this point I may bump the charge limit to 90% or 95% because limiting to 80% and 85% has not helped with capacity loss after one year. I may wait another six months to decide on that, though.
[edit] Four months later, in addition to changing the charge limit to 95%, I’ve also gone back to almost-always power delivery USB-C fast charging. The only time that I don’t is when I charge in the car, which I rarely do, or when I use a charging battery pack, again, which I rarely do. Using slow-charging with USB-A, to me, did not prevent the battery from losing capacity, and setting the charge limit to 80% (and the 85%) also did not help prevent capacity loss.
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You must’ve never traveled or ever use an eSIM :-)
I’m not sure why you say that? I’ve used an eSIM exclusively since 2022 and this year I’ve traveled four weeks overseas, plus a week visiting family, with two more weeks of travel planned this year. Sometimes I’ve had two eSIMs installed but since my Verizon plan now includes an international data plan I haven’t needed to add a data plan while outside the US this year.
My problem with all this is how hard it is to measure actual benefit. I’ve been charging to 90% pretty much since I got this 15 and now it’s showing 276 cycles and 90% capacity. 90% does not sound outrageously good after two years, nor does it differ substantially from what other people report who have been using other charging levels, including full charging to 100%.
I’m starting to wonder if this is once again one of these issues where you can obsess all day long and everybody has their own 100%-guaranteed-to-work secret sauce but in the end it hardly really matters, either because other uncontrolled factors play just as important a role or because all these various battery coddling strategies just don’t really do a whole lot for the average iPhone battery.
I’m reminded of portable Macs where for years people have peddled all kinds of strategies and there is an entire zoo of apps designed to monitor and improve battery health, but in reality, the best is to just let macOS do its thing and enjoy your Mac rather than obsessing over the nitty gritty of its battery.
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I can be obsessive about battery longevity. I have a number of tricks and guidelines and rituals and incantations and such, and have kept some batteries alive for unreasonable periods of time. For ordinary use cases, though, the incremental gains – especially now that vendors have added more intelligent charging strategies to default firmware – is to just use the darn thing.
The only exception that is at all common is if you want to have a device in long-term storage, particularly if it predates intelligent charge limits. I have a couple of Chargies that I use to keep my ancient, decommissioned phones alive for experiments. Otherwise, I think complex charging rituals are just an unnecessary source of stress.
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I got a 15 Pro on release day in 2023, and used the 80% charging limit from the time I got it until a few months ago, when I bumped it up to 85%. I’m at 609 cycles, with 94% maximum capacity (where it’s been for several months). My charging is a mix of MagSafe (mostly overnight) and slow USB-C charging at desk.
I’m tempted to keep the phone for another year, but my T-mobile plan is structured around 2-year replacements, so keeping the phone after it’s effectively “paid off” later this month won’t actually reduce my bill. The plan below mine would lose some money-saving benefits as well - that is, it would reduce my bill by about $30-35/mo, but it would also lose at least $18/mo in benefits, plus a number of hard-to-price intangibles - so downgrading isn’t that attractive.
So, it looks like I may get a new phone this year, and somebody else will get my “very-gently-used” blue titanium 15 Pro.
Apparently, the benefits of limiting charging to 80% on the iPhone 16 aren’t any more pronounced than on the 15:
I now have two years of data with my iPhone limited to an 80 percent charge, and I don’t think it’s been worth it.
What’s your iPhone battery capacity and cycle count? Let me know in the comments below, and weigh in on whether you think the 80 percent charge limit is a good idea.
If you’re looking for more anecdotes, there are over 600 comments posted to this article 
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A further update: after 18 months of limiting charging, the 15 Pro is at 91% max capacity after 384 charging cycles. The 13 Pro, which did not support charge limit, after 18 months was at 95% maximum capacity.
So, to answer the question, I think that the 80% charge limit does not increase life span.
I’ve now switched the 15 Pro charging to 100% charge limit (which includes optimized charging - it holds the charge at 80% during overnight charging and starts full-charge so that it will be fully charged when your normally wake up.)
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I have problems with concluding anything. The only thing I really believe can make a difference is to have the phone on the charger as much as possible.
Adding Apple’s take on the subject with this screenshot.
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I think it is difficult for anyone except Apple to collect enough data from the field and to contextualize it with how Apple software and hardware interact with each other to optimize charging and battery life. Beyond general battery bahavior, there also is a question of how batteries may behave in different device models and under different use cases. At a minimum, the battery data Apple collects surely dwarfs any data collection by third parties.
Consequently, it is one area of technology that I’ve decided to stop caring about. Sure, if I know I won’t have access to a charger for awhile, I will charge to 100% and enable some settings to lower consumption. Aside from that lone scenario, I now just accept Apple’s recommendations for “optimized charging” for routine use. Apple software clearly is actively managing charging processes, so at least in this area, “fighting the software” is not likely to help.
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Just a comment here: this very week I received the “service recommended” notice for battery replacement on my 5-year old MacBook Air. In stark contrast, I have a 10-year old MacBook Pro whose original battery is still going strong!! 