Originally published at: Does Limiting an iPhone’s Battery Charging to 80% Increase Lifespan? - TidBITS
Juli Clover of MacRumors used a new feature of the iPhone 15 lineup to restrict her iPhone 15 Pro Max from charging over 80% for an entire year. It was an inconvenience, but it may have slightly improved her battery longevity.
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I set up the 80% limit when I got my 15 Pro in March; now with iOS 18 you can set it higher, so I have it set to 90%. [edit a week later - the battery app then suggested setting it to 85 instead, so I did that]. I did this deliberately - I always keep my phone for 30 months, and if limiting now gives me even a few percent more capacity 24 months from now, when I’ll buy my next phone, then I’ll be happier.
I’ve never run out of battery even with the 80% limit in the 6 months since I got the phone - not even close.
Yes, it’s an experiment. I’ll compare my battery health degradation to my previous phones over the same amount of time to see if it’s really different.
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95% on 323 cycles from September 2023 to September 2024.
I never set a limit but turned on Optimized Charging. Initially, my charging was mainly overnight on a MagSafe stand. The phone would charge fairly rapidly to 80% and then, at about 4 or 5 a.m., charge more slowly to 100%. In recent months, if I didn’t charge during the day, the charge would be below 30% in the evening, so I would put it on a MagSafe charger for 30 minutes to an hour to get through until bedtime.
I always buy AppleCare+ from my mobile devices and laptops, considering it a reasonable tradeoff given what Apple covers, so I can replace the battery when it drops below 80% at no charge within two years (or longer if I use the new ongoing AppleCare+ option).
I don’t know what I’m doing in the last few months, but even with 91% capacity and charging to 100% overnight, I routinely get down < 20% or < 10% in the evening. I do listen to podcasts and play crossword puzzles. Obviously, the solution is to use my iPhone less—if I’m running it down to empty, that means I spent too much time with it that day!
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I read the original article and found it very confusing. Which results are the benchmark? Which are the test? This is like a graph with no labels.
And, what are they comparing 80% charging to? Optimized charging or the old “charge to 100%” option?
And, I don’t think any of the reported results are that impressive. Because, my 3 year old iPhone 12 mini has 92.1% capacity with only 97 charge cycles. Beat that!
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FWIW, my 13 mini (approaching 3 years old) shows a maximum capacity of 80%. This is charging it every night (using the Optimized Charging feature), rarely charging it during the day, and running the battery down to about 30-50% most days.
Since I can’t directly read the cycle count from an iPhone 13 (why, Apple, why?) I used this shortcut to pull the data from the phone’s analytics logs. It reports:
- Original maximum capacity: 2488 mAh
- Nominal (current) capacity: 1908 mAh
- 578 charge cycles
This yields a maximum capacity of 77% (1908 / 2488)
The official maximum capacity for an iPhone 13 mini’s battery (according to iFixit) is 2406 mAh. Which would yield a capacity of 79% (1908 / 2406).
The power management chip built-in to most rechargeable Lithium batteries can report its capacity, in units of mAh (milliamp-hours). The percentage capacity reported should be this capacity divided by the manufacturer’s spec for the capacity of a new battery.
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I meant, if the point of the article is that 80% charging doesn’t increase lifespan, I’m asking compared to what? Are they comparing 80% to optimized? Because Optimized also limits the maximum charge, most of the time.
Charging to full stresses the battery more and causes more capacity loss over time than charging short of full. This setting lets you manage this automatically rather than watching your phone hit a certain percentage and removing it from the charger.
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I see. I assume this means compared to not enabling any charge limit - letting the iOS algorithm do its own thing, either with or without the “Optimized charging” feature being enabled.
Optimized doesn’t actually limit the maximum - it still charges to 100%. What it does differently is that it uses usage history to determine when you’re likely to remove it from the charger (e.g. when waking up in the morning) and uses that time to calibrate its charging schedule:
- Fast charge to 80%
- Pause charging
- Resume at trickle-charge speeds so it reaches 100% about an hour before your “remove from charger” time.
At least that’s what happens on my 13 mini. It may have changed for newer models.
But I personally think these different charging schemes don’t affect all that much. I think batteries take much more damage from deep-draining and overheating. If you can put it on a charger when it gets down to 20% or so, and keep it from getting hot (no car dashboards, don’t use it in bright sunlight, which overdrives the display), that will go a lot further than funky charging algorithms.
That is, the funky algorithms may have benefit, but if you’re running the battery to zero every day playing games, that’s going to kill your battery a lot more than charging it to 100% afterward.
iPhone 12 here. 546 cycles, 88% of original capacity. Woo-hoo!
I have a Shortcut that announces when battery charges to 80%, and I try to remember to disconnect. But I’m hardly religious about it, and often let it get up into the 90s.
I’ve had my iPhone 15 Pro Max set to an 80% charge limit since getting it last year. It shows a cycle count of 169 and maximum capacity of 99%. But I’d charge it to 100% if I was away from power for a while.
I do most of my charging via MagSafe overnight and during the day, although in the car I attach it to the charging port while using CarPlay.
I can’t say I find this an issue - I don’t have a problem getting through a day.
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92% capacity seems good, but 97 charge cycles can’t be right. That would mean you had only used the equivalent of 100% of battery life 97 times over 1100 days. I’m not sure if that would be possible even for an iPhone that was turned on but never used.
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It’s actually typical for me. For example, when I sold my iPhone 8 after around 3 years, the battery was at 97.9% with only 117 cycle counts.
For a Li-ion battery, a cycle count isn’t “charge, then a discharge”. One cycle would be to discharge fully to 0%, then charge fully to 100%. If you discharge to 50% and then charge to 100%, that’s a half cycle.
What I do is unplug the iPhone in the morning when I go to work, then plug it back in when I get home. So the only time it is discharging is during the day, 5 days a week – or when I’m out and about. (And even less now, since I’m working from home half the time.)
When I get home, the iPhone is typically still at an 80% charge. So I’m effectively using around 20% 3 days a week. By my math, that works out to 93 charge cycles. So it is pretty much in line with expectations.
(I don’t watch videos or play games on my iPhone, so I"m not doing stuff that is a real drain on the battery. I’m not on the phone all the time – I use real computers for Safari, mail, messages, and everything else. I’m not constantly tweeting, snapchatting, instagramming, tiktoking, or whatever else the kids do these days. With previous iPhones I was always able to go 2 days before needing a recharge.)
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I was thinking of my MacBook Pro. Optimized charging limits it to less than 80% (i.e. puts charging “on hold”) because it recognizes that it is rarely used on battery.
Just to add another data point. iPhone 15 pro, first use Sep. 2023 with a July build date. 80% charge limit set from day 1. A handful of charges to 100% but very few. Currently 100% capacity with 201 cycles.
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And another: 80% limit on an iPhone 15 Pro, with very occasional charging beyond that. Max capacity reports as 97% with 254 cycles since last September’s first day on sale.
I usually only stick it on charge overnight, on a MagSafe charging puck. But sometimes charger earlier, if I’ve been playing music or doing something else involving heavier use.
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Another variable that (IMHO) seemed to be missing from the article is to what extent the phone is discharged before a recharge action - does a frequent ‘top off’ say from 65-75% vs. recharging when the phone is less than 20% make a difference? I use the 80%-optimum on my 15-Pro, so the article satisfied my curiosity about the potential benefit. thanks.
That’s actually a point that I haven’t seen any even semi-rigorous studies investigate: how do all of these different charging and discharging habits actually affect battery life? It’s easy to make a general recommendation of charge only to 80% and don’t discharge below 20%, but the reality is that everybody’s usage is different in so many ways that it’s really hard to say how much any single part of it is going to affect any particular person’s battery lifespan.
It would be a mammoth undertaking, but I would really love to see a study that tries to take into account a wide variety of variables on charging and usage to come up with something that’s more meaningful than the current one-size-fits-all-but-not-well advice.
In addition to limiting my charging on my 11+ month-old 15 Pro Max to 80%, I also use a Shortcut to automatically put the battery in Low Power Mode whenever the charge drops below 80%. I use MagSafe for charging overnight.
Maximum Capacity: 99%
Cycle Count: 197
Wow! I agree, your numbers sound right. But that’s a highly unusual usage pattern—I’ve never heard of anyone doing that with an iPhone.