The iOS option to charge battery to "80% Limit" shouldn't just be for iPhone 15 | Hacker News Reader

The iOS option to charge battery to "80% Limit" shouldn't just be for iPhone 15

keydiscussions.com

113 pointsspenvo165 comments

I have an iPhone 13 mini as my "work phone "and it's indisputably a fantastic, efficient, small phone. However, I am kind of OCD about keeping it between 40-80% charged, which is a lot of manual toil.

Conversely, I also have an Android Galaxy S22+ for my personal phone. The "Battery Protect" feature limits charging to 85%. Life is easy with this device and it causes me a lot less anxiety.

Really now, why can't Apple enable this for older phones? I don't believe there's any good reason to force batteries to excessively damage themselves. I had a previous iPhone 13 mini I was less careful with on the over-charging front, and the battery performance was markedly worse. Hence the OCD. I acknowledge my neuroticism, but try to curb it within the realm of evidence.

For a while I had my phone charger plugged into a smart power outlet and a shortcut to turn that smart power outlet off when the phone's battery hit 80%. It would then turn the power outlet back on at 2pm the next day for it to be ready.

Are we not spose to fully charge our 13 minis? I ask cuz i used to run to like ~5% and then charge but not unplug till it was back at 100% this worked well of my last SE even tho people said i was "doing it wrong". Why cant the phone itself know the best defaults, or is it planned obsolescence? Serious question.

It is not planned obsolescence, just that in the case of a phone, having it at 100% when you are out and about might be worth a shorter life for the battery.

I am mostly speaking from experience with EV batteries. The most wear happens in the top and bottom of the battery state. The battery will last the longest if it sits around 50%.

This is true of Li-ion batteries in general.

I also use the shortcuts app, but since I dont have a smart outlet it just send me a notification (on my apple watch) when battery charge is above 80%. I also have another shortcut to notify when battery is bellow 20%.

Many people charge overnight while sleeping, so that would be really inconvenient.

Fellow OCD-ish charge watcher here. Has worked great for my aging iPhone.

What grinds my gears though is the AirPods. I have AirPods Pro that I want to last a long time, but out of the case the earbuds are always 'on' and drain battery relatively quickly (much faster than a phone left idle); put them in their case and they're almost always* charged to 100%. I want to be able to leave them out, off, and disconnected. I almost never need 100% battery in my day-to-day use and there's no replacing the batteries in them once they're worn out.

An 80% max charge limit would be great.

*They do offer 80% overnight charge protection, but that's irrelevant as I don't keep them plugged in overnight

I just use my phone. The battery can be replaced.

Sure, as long as you don't mind messing up / sacrificing the IP69 waterproof seal integrity.

Ask me how I know *cries softly*.

I actually don't terribly mind that, mainly because in almost 15 years of owning a smartphone I've never dropped one in the water. I feel pretty comfortable not having waterproofing as a result.

Well, I really like a nice bath at the end of the day. Different strokes and all that, more power to you bigstrat.

I guess I'm genuinely surprised someone would even want to bring their phone into the bath. I do enjoy a bath rather than a shower on occasion, but I'm just enjoying the soak all by itself. But hey, like you said, different strokes for different folks. I certainly understand why the waterproofing is a concern for you if you're regularly using your phone over water.

Why does it mess up the seal?

Are you saying Apple doesn’t re-seal it properly?

Battery charging is often controlled in "hardware" and OS don't have full control(else a software crash could easily cause fire). Some hardware implementations can be instructed to stop charging immediately or stop this time at specific voltage, but implementation varies and the feature is often ignored.

We know the older hardware has that, because the software already controls it on a schedule.

> I am kind of OCD about keeping it between 40-80% charged

Why?

Having the majority of your usage / charge cycles being based on a 50 to 80% total charged will increase the total cycles (and the battery’s total life).

I realize this is true, and sometimes I will charge sooner or stop charging earlier to keep my phone in this range. But most of the time, I just use my phone. After all, what's the point of optimizing the total battery life if you aren't ever going to actually use the battery to its capacity?

If you don't ever use the full capacity of the battery, why wouldn't you want to optimize it?

Because it's one more thing to think about?

85% for daily, 100% for long trip

Artificially limiting yourself to 40% of your battery’s capacity to extend its life seems like an enormous waste of effort

My last phone spent like 8-10 hours a day on and off a wireless charger and had 88% battery health when I sold it over two years after I bought it

I can't imagine caring about my phone's battery health enough to pay attention to not let it charge to 100 overnight.

It's something that should be automated. And even then, I'm not sure I would use it, I usually need 100% of my battery to go through the day.

Apple's "battery health" measure is not the percentage of original capacity remaining. My old iPhone X claims 81% battery health, but the actual capacity is more like 60-70% of original.

I'm pretty sure 88% health means like 80% original capacity since iPhones actually shut off at 20% real capacity to protect the cell.

Assuming that’s correct, by me not janitoring my battery for over 2 years I still have double the capacity of the guy who I originally replied to

I really do not understand how that’s worth “a lot of manual toil”

A 10-80% load cycle will be almost as good as 50-80%, and much more practical.

> "I am kind of OCD about keeping it between 40-80% charged, which is a lot of manual toil."

You shouldn't worry too much about going below 40%. Regularly draining it to zero might shorten battery life, but going down to 10-20% won't.

> " I don't believe there's any good reason to force batteries to excessively damage themselves."

From Apple's perspective there is. Selling replacement batteries is very profitable.

10-20% will definitely reduce cycle life. you would almost double your cycle count by keeping your battery above 40% vs 20%

This has far less effect than limiting charging to 80%. If only because you usually spend a short time down at 10% before noticing it's low and finding a charger. Where as phones regularly spend long hours charged to 100% because we tend to put them on chargers and then leave them overnight.

Cycle count is virtually meaningless. I have a MacBook Pro with almost 1000 charge cycles and it’s got ~93% battery health after 8 years.

Lithium batteries are happiest around 40% state of charge. The closer you can keep them to that magic number the longer they’ll last. But leave them fully charged, or even worse, fully dead and that’s the quickest way to kill them with “normal” use.

That's very impressive! My Macs are usually down in the 80-85% range after 500 cycles. Do you use any tools to limit charge state other than "optimized battery charging"?

My Pixel 6 doesn't seem to have this option.. I never looked into third-party apps for it though.

I highly recommend AccuBattery for Android. I have been using it for a few years now and I saw a noticeable difference on my Pixel 3a XL compared to use on previous smart phones. I now have a Pixel 6 and its nearly 2-years old and the battery lasts well beyond 30-hrs with combined use.

https://play.google.com/store/apps/details?id=com.digibites....

My previous phone was an iPhone XS and its battery was also completely fine for 2 years. Year 5, I definitely noticed a drop in battery life. If you're planning on keeping your phone for 5+ years, definitely do the 80% thing. If you're on a 2 year upgrade cycle, it probably doesn't matter.

> This app may collect these data types Location, Personal info and 3 others

I don't think there's a way to manually limit it to 80% within Pixel's settings. If you turn on Adaptive Charging, it'll charge it to 80% overnight and bump it to 100% just before you unplug your phone in the morning.

https://support.google.com/pixelphone/answer/7106961

> The difference is that Optimized Charging kicks in only when your iPhone is normally idle, typically overnight. The new 80% charging feature (that’s limited to iPhone 15 models) doesn’t try to be as smart, and simply works all day long.

That’s not how the Optimized Battery feature works, according to the help text displayed right next to the feature in the Battery Health settings.

I question the whole premise of this article.

Edit: Ah, I can see how you thought my wording was confusing. The feature "kicking in" is that it is not charging (when it typically would be charging). But it could sound like I meant that it's charging when idle. Rephrased to be clearer, thanks. --------

Author here, I think my Optimized Charging description is a fine description of how it works in practice. To borrow from another publication: "Optimized battery charging is a feature on iOS 13 or newer that limits overnight charging to protect your phone's battery in the long term." [0] With it, iOS learns your habits and will try to keep your phone charged under 80% until soon before it thinks you will take the phone off the charger, when it tops it off to 100%. "The algorithm aims to ensure that your iPhone is still fully charged when unplugged." [1] I have also used the feature personally since it came out, and this is how it works. What do you take issue with specifically?

[0] - https://www.pocket-lint.com/what-is-optimised-battery-chargi... [1] - https://support.apple.com/en-us/HT210512

Author again, “I question the whole premise of the article”

What? You got tripped up on my wording, sorry. But the article's premise is valid, and it's not cool that the top comment on this submission for its first three hours on HN has totally lacked curiosity and come to a sensationalist conclusion. Do you have any actual problems with the article? Could you list them? (You responded to others but not my previous comment)

Do you have any evidence to back up your claim that there is no hardware or inaccessible firmware difference between the iPhone 15 and 14 which might suggest a different charging strategy and/or limit their ability to roll this out to earlier versions? Or are you just spitballing here?

Hey! (thanks for expounding on your concerns).

The claim from the article is that a fixed 'charge to 80% feature' is "likely possible on earlier models". I asked Apple to comment and am curious what they say. We do have evidence for the article's claim: iPhones dating back to at least the iPhone 8 support a feature that limits charging to 80% for multiple hours per day already. It just only occurs during hours Apple chooses via its learning algorithm. I never claim that the hardware is/is-not different; you simply have to look at what is already supported to understand what the devices are capable of.

> That’s not how the Optimized Battery feature works

Please say what the difference is, then?

It slows down and times its charging to reach the 100% right before you get up in the morning, rather than immediately after you plug it in (which would make it 100% all night long).

So in other words, the limiting only works overnight.

So, again, what is the difference from what you quoted? Is it the implication that it might work at other times of day when the phone is "normally idle"? I don't even know if that implication is true or not, since it depends on exactly how the phone calculates your schedule. But if that's your complaint, it seems pretty small to me, not enough to throw the rest of the article into question.

Is there something else I'm missing?

Optimized Battery will charge your phone to 100%.

Right, once overnight is ending. It only optimizes overnight, with the battery limited the vast majority but not right at the end.

I don't see the conflict.

It doesn’t work if I plug my phone in at 9am in the morning. It will charge my phone to 100% immediately in that case. Even if I leave it connected to power all day. Breaking my battery.

Optimized charging is based on learning and thus unpredictable and hard to influence. It only works if you have rigid habits.

The article says it only works in that situation, not that being in that situation is a guarantee of it working. I think the phrasing is fine. Do you disagree?

Like, if I say my car only starts when it has gas, I'm not promising it always starts as long as it has gas.

It's far from a comprehensive list of things that break the feature, but it gets the point across that the existing feature does a fraction of the job at best.

No, it works any time of the day. It just depends on your charging habits. And it also depends on your location, if you’re away from your primary location, it still charges to 100% when plugged in during your normal charging times.

The article says it only "kicks in" at certain times.

If your argument is that it "works" all the time even when it's not affecting charging, therefore the article is wrong, you are splitting hairs in the worst possible way. And if you're not arguing the article is wrong you might need to reread the comment thread.

It’s close enough for the purpose of the article.

I can't imagine caring about this honestly. The way i feel it is like constantly caring if your white shoes are dirty, i only trust my shoes to help me walk.

Technology should be as transparent as possible in my opinion and not bring us back to thinking about said technology, just what we can do with it.

It's tiresome enough to worry about having a charged phone, i couldnt bring myself to look at battery percentage or even phone charger options just because i am calculating how long will my phone last in the long run.

This is just an optional feature, nobody is forcing you to turn it on, or to care about it. Personally I rarely need a 100% charge: my iPhone 13 easily gets through a typical day with 40% remaining. But I do get annoyed when a phone is 2 or 3 years old and the battery is already worn out. Genuine iPhone batteries are expensive, and limiting charging to 80% will significantly extend their life.

Worn out batteries don't just have limited capacity, they charge slower and create more heat while charging due to internal resistance. I'd much rather charge to 80% for my typical day, but have the option to 100% charge on those rare occasions when I know I might need it (long day travelling, etc).

While not ideal, maybe we could have more trickle chargers? My worry is that the battery actually gets used often but for short periods and that could effect long-term wear.

Personally, I have a Shortcut to put my phone into "low power mode" once it hits 90% (why not?).

Maybe a Shortcut could do the same and turn off power once it hits 80% on your overnight charging dock and then use a small amount of power while the screen is off.

> Personally, I have a Shortcut to put my phone into "low power mode" once it hits 90% (why not?).

Isn't low power mode for when your phone has very little battery left? I don't understand why one would put a phone in low power mode when it's charging and hits 90%.

That's the original intent, but there's nothing stopping you from enabling it whenever to try to get the absolute max possible out of your battery. Low power mode does sacrifice quite a bit of functionality by default though.

Personally, my 15 pro can do >72 hours on a single charge WITHOUT doing stuff like this, even starting at 80% (note: mostly standby, no always on display, with ~3h screen on time total). The 80% limit is definitely something I'll be using virtually all the time.

Oh sure, I put my phone in LPM sometimes when I know it's going to be a very long day. But why would someone put it in LPM when it hits 90%? Is that referring to when it charges up to 90%, or when it's in use, unplugged, and is "down to 90%"?

The latter.

For me, I find the performance/lost functionality fine: https://support.apple.com/en-ca/HT205234

On the other hand, I’ve pretty much stopped using LPM after getting a 14 Pro and getting used to the higher refresh rate of the ProMotion display; I find the slower refresh rate really jarring (I also have a non-Pro 14 which I don’t like using for the same reason).

If iPhones have replaceable batteries (the kind you can slot in and out) then you’d be right.

Replacing an iPhone battery at an Apple Store costs about 1/3 the price of the phone by the time you need it replaced, so ideally one would want the battery to last as long as the lifetime of the phone. One way to delay liion battery ageing is to shallow charge.

Case in point I’ve a 6 year old dell laptop that is set to shallow charge to 75% in BIOS and the battery still holds 3 hours of charge (from 75% to forced standby)to this day. Most laptop battery stop holding a charge 2 to 3 years in.

>Most laptop battery stop holding a charge 2 to 3 years in.

Counterpoint. I have a lenovo thinkpad t480s that I bought second hand and is now 4+ years old. The battery lasts at least 6 hours. I haven't discharged it fully in a while to be more precise. Ubu 22.04 running in power save mode as selected from the default gnome menu.

Dell? Yeah, terrible company making terrible laptops for sure. Used to think differently before owning one.

IME, an iPhone battery lasts minimum 3 years. (I've actually never needed a new battery the ones I've owned). $99 over 3 years is $0.10 a day. I'd easily pay that for an extra 20% battery capacity and it's definitely not worth fussing over.

1/3 the price of the phone?

An iPhone battery replacement is $49-99 at an Apple Store.

The rest of that was,

> about 1/3 the price of the phone by the time you need it replaced

So that sounds plausible if iPhones can be purchased for $150-300 at the age you'd replace the battery. (Though that does strike me as a little low, still? Depending on how long the battery lasts...)

How is that logical? Why would you buy a phone for $150-300 that’s the same as the one you have, likely with ann old battery for that price, instead of replacing the battery for <$100.

We have phones plugged in 24/7 for work. The phones where I can limit the battery charging have never had expanded batteries. The ones that cant expand regularly (sometimes as little as 6 months).

Personally i hate the optimized battery charging ios does. It’s awful. I’d rather being able to keep my phone plugged in basically 24/7 and always have it ready to go, but not have to worry about expediting its death.

It is possible to use something like Chargie to limit battery charge if you want to keep your phone plugged in.

Related: for MacOS, AlDente allows you to set a battery charge limit.

https://apphousekitchen.com/

I've been using it successfully for around a year. It works pretty well sans a couple quirks due to hardware limitations e.g. if you plug in with the screen closed (sleep mode) it will charge fully to 100%.

AlDente is fantastic, does it exactly what it claims to with no fuss. Happy to pay the 20 bucks or so for a lifetime license.

For my main computer (M1 Macbook Pro) that spends roughly 80% of the time on its charger, I have it set to 65% which gives me plenty of margin at home, plus it allows you to top-up to 100% on the pro version with one click.

For my 2015 Macbook Pro with heavily degraded battery that spends 100% of the time on its charger and on, I set it to 50% to (hopefully) lengthen the life of the battery before it swells since removing the battery safely is a bit sketchy on even that era of Macbook.

This makes sense. There are 3 “ways” a battery charges.

1. OS’s battery driver does the charging. This is possible when the computer is on and the driver has control. 2. Firmware driven charging. Typically used in sleep mode 3. Analog Trickle charge - no intelligence, no code is executing. Charge slowly from a dead battery so as to not damage any components.

#1 is the only case where an app. Can control any aspect of charging.

That's true. I evaluated it, but it wasn't of use to me as I keep my Macbook plugged in with the lid closed.

I eventually tried this instead (for Intel Macs) :

https://github.com/DevNulPavel/osx_battery_charge_limit

I use it to keep my battery level indicator pegged at 70%. Often doesn't persist after a system update, but it's just a quick terminal command to reapply the setting.

I use my Macbook in clamshell mode, and I use sleep mode when I'm not using it - receiving power from a Thunderbolt dock. It's handy to pick up exactly where I left off on resume. Plus, I use two LG screens where one of the two doesn't switch on after a cold boot, and it's annoying to unplug and replug to activate it. Sleep mode gets around that.

Wondering if third-party software like this, when not baked into the OS, will have other longterm side effects. Since it can't really put a hard-stop on charging, can it?

Al Dente just sets the charge target via SMC and lower level software handles power draw negotiation. It’s the same thing the OS uses to set the target to 100% or 80%.

Same. I have mine set to sit at ~50% while plugged in & still have 100% of my battery health.

It’s an M1 Pro MacBook that I’ve had since launch.

I've also been using it on a 14" M1 MacBook since launch (Oct 2021). I'm currently at 86% battery health.

I keep it at ~80% limit normally with occasional charges to 100% for long trips, etc. I do spend a lot of time on battery though so it's charging and draining a lot, but rarely goes above 80% charge.

Thanks for posting your results, I'm curious just how much the charge limit helps battery longevity.

I wish I had discovered it earlier... I'm at 90% battery health on the same model which I use plugged in the vast majority of the time.

This happens under Asahi Fedora KDE too.. I think it's the battery controller that works outside of the OS?

AlDente has a new competitor with less paywalling: BatFi. I find it nicer to use.

https://micropixels.software/batfi

In the meanwhile, there's https://chargie.org/

I have an 11 pro as my main workhorse. Multiple years old, constantly running the battery to 2 % then charging to 100 and it still lasts all day for me. I feel like the concern I see going on in this thread might be a bit misguided.

If we are sharing anecdotes, my wife and I got iphone xrs same Xmas. She regularly fully discharged hers, whereas I charged mine throughout the day. My phone very very rarely goes below 40 or even 50 percent. After couple of years, her battery life was awful and mine was fine.

Basically, I find individual stories vary, but statistics may show overall trends

My 11 pro was the same way. And then I got a 14 pro.. it has noticeably worse battery life, I suspect in part due to 5G which I have since disabled. I tend to keep it on the charging stand on my desk for video calls as it now has magsafe (or whatever it's called). It's constantly charging to 100% and I'd love to have a way to stop it from charging without having to remove it from the stand like a cave person.

Thanks Tesla for bringing about lithium battery health awareness to the masses. Without it I would be charging to 100 every night. And blowing out my battery way too soon.

Arguably, it’s a misfeature of Teslas. My BMW i3 has a hard charging cap of 90%. (The UI scales the charge percentage and displays 100% between 90 and 100%)

It’ll regen charge up to “really” 100%, but that would require something like a 5,000-10,000 ft continuous elevation drop, where you just ride the regeneration brake the whole way down.

Nissan took a different approach. The batteries on the old Leafs died really prematurely because they didn’t have decent battery management.

They fixed it on later models.

Anyway, this stuff is mostly a solved problem these days. It would be nice if device manufacturers were compelled to provide an 8 year, 80% capacity parts and labor warranty on all non-replaceable batteries (like the car manufacturers do in the US).

It's very different when you are dealing with a $1000 object versus a $40000 object, where the replacement of the battery could cost $300 and $20000 respectively.

Are we talking about phones and cars here? What phone costs $300 for a new battery? I assumed Apple would be on the high end, and they charge a fraction of this ($100ish, IIRC).

That was only an example. My argument is only strengthened when you use the actual cost of battery replacement.

Gotcha — just making sure I wasn't missing the comparison.

These kinds of features being so limited annoys me.

Like GoPro can only auto clear a video from your sd card that has been uploaded on the newest model. There is no way that is limited to those devices. But, it probably isn't profitable to even crack open the code for the older models so they don't even consider it. It makes it worse because I'm even paying a subscription for storage.

It's much worse in this particular case. They purposefully had to lock the feature behind a device flag to prevent older phones (that still support the newest OS) from using it. I'd expect that they could easily enable the feature for all phones that also support Optimize Battery Charging.

I am a user of Samsung Galaxy and Apple MacBook Pro M1 Max. Both models offer Battery Limit/Battery Protect features to protect the lithium-ion battery. I first realized that other iPhones, except for the iPhone 15, don't have such a feature. Maybe it's a good idea to include it?

Apple doesn't really care about their iPhone customers. They prefer milking them for more money by forcing them to buy a new model instead of adding a feature that would actually help the environment which they often lie they care about.

For rooted Android phones, there's ACC:

https://f-droid.org/en/packages/mattecarra.accapp/

That is AccA though, the unofficial frontend.

You still need the actual acc app: https://github.com/VR-25/acc/

It's also a setting supported natively on Samsung devices.

I suspect it's mostly because of the exploding Note fiasco. But it's a great option to have.

I have this feature enabled at all times, but my iPhone 15 Pro (with always-on display) usually can't make it through the day. Still wondering if limiting always to 80% will actually increase longevity of the battery

Go into the shortcuts app and create a shortcuts that turn off wifi when you leave areas where you use it and turn it back on when you return -- this will prevent the wifi radio from searching for APs constantly. Go into settings and check all your apps for background refresh -- there are probably a bunch that don't need to be constantly for new content when you aren't using them. Switch to Brave Browser instead of Safari -- the built in ad blocking will save CPU cycles on websites. With all of these set you can probably get another ~1hr or maybe ~2 if you have some egregious apps refreshing and a whole lot of APs you can't log into that keep coming in and out of range.

Deep cycles are also bad for batteries.

Honestly, I’d suggest trying to use your phone less. A new 15 pro has a pretty ridiculous screen on time even at just 80%.

If GP is like me where I always run an app tracking my location (with my consent) in the background, even using the phone for 1 hour per day would drain the battery from 100% to 30%.

i barely get through the day with a fully charged phone, and i don't get enough runtime if my laptop is not fully charged.

so i'd like to know more about the science behind this. how much does the battery life actually improve by doing this. is the trade off worth the inconvenience of a shorter runtime before i need to recharge?

It's for people who only use like 40-50% each day. Going from 50% to 100% puts more strain on the battery than going from 30% to 80%, so limiting the total charge allows the maximum capacity to last longer (in terms of years) than otherwise.

And if you do ever need all 100%, just turn off the limit the day before.

For me it's a no-brainer: 85% on my current (brand-new) Android phone lasts around 50-55 hours.

I wish they made the batteries slightly larger, then made 100% on the battery meter secretly be 80% of the increased capacity so I could have my cake and eat it.

They almost certainly aren’t driving them to 100% physically possible, just like they aren’t draining them to absolute zero.

The cutoff points are going to be picked to balance lifespan and capacity.

I'm pretty sure Samsung does a fake-out like this to display your 80% charge as 100. (Samsung.tablet at least)

The phones display 100% at like 98-99%.

The Android API allows you do get the voltage and current of the battery (with negative current for discharging and positive for charging), so there are apps out there that tell you the real state of the battery when it's in that range. The phones will tell the user fully charged before it's actually completely charged, but it's not much. It's mainly so if you leave it plugged in, it can cycle a bit up and down while still displaying 100% instead of continually trickle-charging.

My guess is tablets would be similar, but I've never had one.

It's best for users that UI never displays true SoC(state of charge). They will not understand that the cameras and NFC payments don't work under true 10%, your degraded battery cannot safely reach nominal 100% voltage, etc.

Those are not pleasant facts that users need always be made aware of. 98% understood by BMS rounded up to 100%, actual 12% displayed as 1%, etc., should be tolerated.

Samsung phones stop at 85% and show 85% (if you enable the option "only charge up to 85% in the settings).

I would be unhappy if my phone has 20% battery left but I can't make a call or check map/WhatsApp.

I kinda meant on the top end (So it never charges so high that the battery experiences increased wear).

But... this happens at the bottom end too, your battery already still has some charge left at 0%, the BMS protects it from being fully discharged. I'm just wishing there was a bit more so I don't have to make decisions about wearing out the battery faster.

Then I could enable OVERCHARGE and get 120% charge for travelling or when I know it's going to be a long day, at the cost of battery life.

iOS already does something like this. After the phone turns off from low battery, it’ll still allow you to use Apple wallet for a few hours.

It's a bit similar, but it sounds like that's less than 1% of the battery.

I already expect my phone to die fast when it gets under 5%.

Going from 85%-25% instead of 100%-25% can increase the capacity by ~25%: https://batteryuniversity.com/img/content/capacity-retention... [0]

https://batteryuniversity.com/article/bu-808-how-to-prolong-...

That's degradation rate in capacity, not overall capacity. But trading off 40% of the energy for a 25% lifetime increase is not a great trade for everyone.

You would then consume almost 2x of those cycles just recharging to make up for the lost capacity.

> Going from 85%-25% instead of 100%-25% can increase the capacity by ~25%

Capacity or longevity?

Both, as a battery ages from use its capacity diminishes which is why it runs out faster.

Limiting charging to 80% means getting rid of constant voltage charging mode altogether. Generally speaking and in illustrative numbers, Li-ion batteries are charged in following manners:

  - Below 10%, battery is charged in pre-charge mode through a 10-foot pole. 
  
  - Above 10%, battery is charged in constant current mode, as in:  
     `charger.current_max(battery.CAPACITY * battery.CHARGE_C_RATE)`  
     `charger.voltage(battery.voltage + 0.0001)`  
 
  - Above 80%, battery is charged in constant voltage mode, as in:  
     `charger.current_max(battery.TERMINATION_CURRENT)`  
     `charger.voltage(battery.VOLTAGE_MAX)`  

  - `charger.charge_complete` shall return `True` if `battery.voltage == battery.VOLTAGE_MAX and charger.current == battery.TERMINATION_CURRENT`.   

  - * `battery.CHARGE_C_RATE` is generally set within 0.2 to 4; 1.0 matches mAh rating of the battery, a mostly-safe default. 0.2 is 5 hours to full charge, and 4 is "fast charge to 80% in 15 minutes".    
  - * all above is usually implemented in charge controller chip firmware, often in actual ROM; the bare minimum often done in real products is to hardwire indicate `charger.current_max` to the chip in circuits. That suffices unless intricate charging really is one of your differentiation. 
  - * `battery.state_of_charge` is more or less `find_acidity_or_pH(battery.voltage, battery.formulae)`, by the way. Capacity-Voltage curve is titration chart turned sideways.

It is often vaguely told that this constant voltage variable current mode used in 80 - 100% range is harmful to batteries, so not doing it should improve longevity. As to why then implement CV modes at all, and why not offer an option to easily disable it, I don't know. Everyone does it this way. I wish I knew if altering `battery.VOLTAGE_MAX` would work or if `charger.allow_cv_charging` can be set to `False`, but those are often hardcoded `4.2` and `True` in ROM.

It is not fundamentally possibly to simultaneously set voltage and current of the charger as they are inversely related to each other and vary as a function of charge state. As the battery gets more full, the current is forced to decrease as the battery resistance increases (or equivalently the voltage is forced to decrease, or some combination of the two). So those given parameters seem to be more estimates of the capabilities of the charger at various estimated points in the graph rather than actual operational values. Unless I am misunderstanding you?

That is principally correct, and, in fact, a fixed voltage power supply with a resistor in series just works for charging NiMH/NiCd, yes.

In Li-ion however, I think it's something like, max voltage ramp is limited even within current limit, then afterwards current is limited even below cutoff voltage, or whatever to similar effects. It's definitely more complicated than just constant max voltage fed through a 330R.

How is that possible? Even charging my phone to 80%, I can still use it for at least a day.

Although my laptop does get a lot more use.

it depends on how you use your phone. when i am outside all day running errands, checking messages, calls, web searches... by the time i get home my phone is usually on the last % before shutting off.

i tend to buy cheaper older models of phones though, that may not have the strongest battery to begin with.

I buy cheap android phones with large batteries, it's pretty much my only criteria nowadays because everything else is good enough for me.

The only time I get close to running out of battery is when I'm watching YouTube videos on a long bus/train/plane ride.

Full brightness screen is your biggest killer

Glancing at some comments here mentioning the overnight charging feature working for them, am I in the minority by charging randomly whenever it needs it? My charger isn't even in the bedroom. Curious how my random on/off habits compare to overnighters in long term battery health.

I try to take it off around 80% so I was interested in this feature and confused when the update didn't include it. I don't like that it's in my "pros" column for upgrading when it could be available to everyone, would rather not reward them for that.

The world of lithium-ion battery chemistry is quite complicated, but in my experience, the top contributors to battery wear-out are, in decreasing order of severity:

- Charge cycles (including partial cycles, e.g. 100% -> 50% is half a charge cycle)

- Depth of discharge (deeper discharge cycles are worse)

- Extended periods in hot conditions (over 40 degrees Celsius)

- Extended periods of being held at 100% state of charge

In essence, your charging behavior dings the first two items: higher number of charge cycles, and deep discharge cycles. If your goal was battery longevity, keeping the phone plugged in as much of the time as possible would be the best strategy. Bonus points if your phone supports a "stop at 80%" mode, but still the winner even without this feature.

I think another huge killer of lithium batteries is charging them when below freezing. I bet most phones probably wouldn’t allow it though - or at least would limit it.

I left out things that a typical battery management system will prevent, like over/under charging, or operating outside safe temperature limits. But yes, charging a typical cell below 0 degrees Celsius will immediately and permanently damage it. Here's a ref with some details on why:

https://www.bonnenbatteries.com/lithium-battery-low-temperat...

Li-ion chemistries that are tolerant of charging at low temperatures are a subject of active research.

I would like to see this feature in Macs, too. In my experience, the current "optimised battery charging" option doesn't work well unless you have a very regular charging routine.

Could the decision to support the 80% charging limit for only iPhone 15 be related to changes in battery chemistry? Does the iPhone 15 use a different battery chemistry? I ask because I have noticed my iPhone 15 charges to 80% way faster than my other phones and devices

Unlikely. Virtually all lithium batteries display similar characteristics with respect to charging.

Charging faster is something that can be variable between chemistries, but typically batteries are fine with charging quite quickly in the first 80% regardless, and can be made to tolerate fast charging (though usually you sacrifice a little bit of lifespan or total capacity to increase that tolerance)

I'm pissed that stock Android doesn't have this unless you charge for 4 continuous days

The Chevy Volt has the perfect handling of this: A new car never charges past 90% or drains below 10% battery. It simply reports 100% when the actual battery isn't quite full and vice versa, extending the battery life significantly.

As the battery life degrades over time, it will try to keep the same useful range, and shrink those boundaries until you are using the full battery life each charge.

Perhaps this works less will for phones, but I'm not so sure. Personally I never have issues with battery on new phones. It's only as the battery life shrinks that you really need the full range.

I've never understood why these companies don't just add a redline: make the battery chargeable to 110%.

By default have it stop charging at the recommended 100%, but let the user decide if they need that to go beyond that and are willing to damage their battery health to do so.

> let the user decide

Most users don't know enough about battery chemistry.

WAY too many people don't even understand how USB charging work, their brains are still stuck in the barrel jack charging ages where the charger pushed power and the device just took it (or blew up).

I recently had a battery fail pretty spectacularly in a Huawei 5G router, which had spent most of its short (3 years) life sitting charged to 100%. Admittedly the replacement battery was cheap, but the failed battery was a messy hassle to change since it had swollen up so much it almost blew the housing of the router apart. And potentially dangerous if it had split open or caught on fire.

If Huawei had a "limit charge" feature in this device, it would probably have avoided all that hassle!

I just do this with a Shortcut in the Apple Shortcuts app and a smart plug.

Create an automation when the battery hits 80%, switch off the smart plug.

On an iPad, is it better to keep it plugged in at all time so it switches to AC power and doesn't touch the battery, though battery stays at 100%, or do some trickery with an automated socket to cut charging once it hits 80%, then re-enable power once it's at ~25?

I wonder what's worse for the battery, constantly getting the battery down to 5% and charging it back it to 80%, or letting it go up to 100% and never letting it drop under say 20%.

This reminds me of when water bottle companies reduced plastic by 30%.

Of course unlike Nestle and Coca Cola, Apple is too hip to be known for its environmental impact…

I found this strange as well and have been wondering if there is a hardware constraint that no one is aware, yet.

Why not make 80% the new 100%?

Because there is a trade off here between ease-of-use day-to-day and long term longevity.

Battery is at least 20% too small then. The trade off with making it bigger is not for the user it's between engineering and marketing, which is dumb.

There should be an option to use the charger directly without involving the battery.

On my 13 mini, I just set a shortcut to turn on power save mode when power save mode is turned off.

I also set a geofence around the cell dead spot at my house to enable airplane mode.

The latter spams notifications due to an (anti-stalking?) “feature” of shortcuts that doesn’t let you disable geofence notifications.

That bug can then be fixed by exploiting another bug by enabling screen time, the creating a custom app shortcut that produces a notification. Run the custom app a bunch and screen time will decide it is spam, and force-enable the “disable notifications” toggle for the shortcuts app. (Apparently this doesn’t work on some of the newer/higher end iPhones. My guess is they copy pasted the policy logic for each model, and forgot to backport a bugfix).

The above greatly increased battery life and did so transparently.

Now, all I need to do is buy a smart plug and have it toggle the power on a low-speed charger when the iPhone battery is above 80% or below 60%.

After that, I’ll do the same for my watch and iPad.

Couldn’t be simpler.

> I also set a geofence around the cell dead spot at my house to enable airplane mode.

How?

That's the point. Apple wants other models' batteries to degrade fast so that the users can upgrade to 15

As mentioned in the article, this has been an automated feature since iOS 8: https://support.apple.com/en-us/HT210512

Looking at my battery history, the automated version has my phone sit at 80% all night, and leaves it at 100% for only a couple hours in the morning. I suspect this will be a fairly negligible impact on battery longevity for me, and most users, without the severe inconvenience of a 20% reduction in battery life.

It would be nice to know how the longevity math works out.

Unfortunately, it's not possible to reliably automate this. A phone has no way to tell how it will be used after getting charged. It can try to detect some usage patterns, but it'll just be guessing, so even in the best case scenario it must remain conservative.

This is one of my pet peeves - obvious and easy to implement features that are just not there. I literally only switched to iPhones because the blindingly obvious Emergency Bypass feature [1] wasn't available on Android.

Phones already perk up when connected to a power source. Why not display an optional dialog with a choice of either the desired max battery level and/or some user-friendly modes like "battery health" vs "battery charge"?! Easy to implement, zero downsides, massive upsides, nobody's doing it.

[1]: https://support.apple.com/en-gb/guide/iphone/iph21d43af5b/io....

Another example that this feature doesn't work is charging at car. In other words, it may work only while sleeping at night. It's far better than nothing, but I wish the 80% limit feature is available for my 13 mini.

But apparently they don't care about future sales from iPhone 15s wearing out?

Do you have anything other than context clues to go by when making this assertion?

These discussions are always baseless.

Could Apple have enabled this feature for all phones? Maybe

Would it have provided any use to older phones? Maybe

How much lifespan does it actually add? No one knows

Did they do this as planned obsolescence? Maybe.

There we go, the whole discussion finished.

My X (bought new phone in December when it was released) was at 85+% on the battery.

I replace it with a 15 because it was dropping off the OS bandwagon, needed more storage, battery life, lightning port getting fiddly.

The OS support was the stake in the heart. If not for that I would have looked into getting the phone serviced with a new battery and port, and cleaned up some storage.

I’m still getting OS updates on my X

iOS 17 does not run on the X.

That sucks. The keyboard improvements in iOS 17 make it finally usable.

Perhaps they didn't implement this in their BCM, maybe they were so caught up in the cleverness of "optimized" charging they thought it would solve the problem once and for all.

Unlikely? Yes, however it's not impossible.... and not the only alternate explanation :-)

Something seems off: my 13pro stops charging at 80% on purpose though i am not sure if that is a result of some combination of settings.

If its plugged in long enough, iPads and Macs will let it drop to 80% ... but you can't set that limit initially.

My iPhone 12 Mini sadly has never charged to 80% with that setting enabled... I suspect my usage patterns are too irregular as it is my secondary device and mostly lives on its charger.

Reply on news.ycombinator.com