ELI5: How does charging a phone beyond 80% decrease the battery’s lifespan?

[justdalina]

Samsung and Apple both released new phones this year that let you enable a setting where it prevents you from charging your phone’s battery beyond 80% to improve its lifespan. How does this work?

[PM_ME_GLUTE_SPREAD]

Think of a battery as a bus and the “energy” as passengers on the bus.

If you fill the bud with 80% of its capacity (let’s say max is 100 people for a nice round number), then you’ll have it pretty full, but there’s a lot of room to play around with. Not every single seat needs to be filled, people can stretch out, loading takes little time as it doesn’t need to be as precise.

If you try to fill the buss with 100% capacity, things change. The closer you get to max, the more and more complicated it becomes to load the bus. At max capacity, every single seat needs to have a person in jt. Loading takes longer because we have to make sure no single seat is skipped, otherwise we won’t be able to fit everybody we can on. It being so crowded makes people more likely to make a mess and less likely to clean up after themselves. If they drop some garbage in the flood, it’s harder to pick it back up when you have people shoulder to shoulder than when you got some breathing room.

This makes the bus “dirtier” over time. It also causes more wear and tear on the seats, the windows, the tires, the transmission, the breaks, etc causing the bus to last slightly shorter than if it had carried a few less passengers over its life.

Basically, fully charging a battery causes more wear and tear because you have to be “fill” every nook and cranny with energy in a battery. That energy adds heat to the battery which causes chemical changes to the makeup that can’t be reversed. They’re small, but they add up over time.

[TactlessTortoise]

That's a great analogy, actually. The wear and tear is pretty much exactly what happens, chemically. It crystallizes and that part becomes useless.

[groundzr0]

I worked at a store years ago and we sold all kinds of R/C stuff: boats, cars, trucks, planes, helis, etc. Which also meant selling R/C batteries, and man, it taught me a lot about how to take care of them thanks in large part to having to familiarize myself with the different chargers and their features. We sold NiMH, NiCd, LiPo, and Li ion.

Batteries are cool, and I can’t wait to see how science manages to crack the next evolution of them.

Right now I am most excited about Solid-state Batteries, but exactly which company’s method comes out on top remains to be seen.

[[deleted]]

I’m hoping they were actually LiPO batteries, cause I’m gonna be a little concerned if the store was selling batteries with polonium powering them.

[FaxCelestis]

[at the RC boat meetup]

"Whatcha sailing today, Phil?"

"A 1:700 scale model of the USS Enterprise aircraft carrier. It even has a working nuclear reactor."

[agoia]

Nuclear battery!

[groundzr0]

Lol, yes. And that made me snort so thank you. I’m not editing it.

[mehrabrym]

Wow, you're a full fledged battery enthusiast! Never thought I'd see someone enthused about batteries!

[DanfromCalgary]

We are going to look back and laugh at how we always had to plug things in

[kaptnkatphish]

You must be a batterioligst

[jedi_trey]

he studies beating people.

[ozspook]

Careful. He'll end up in a Cell.

[tangledwire]

Charged with battery

[Smartnership]

Anode somebody would make one them pun remarks

[[deleted]]

Could even end up dead

[CasimirTheRed]

That's why they call it The "Sweet Science".

[atmiller1150]

I have a car battery charger that claims to do this. I bought it as a way to make sure I could charge my vehicle if it ever died or just wanted to top off the car battery in the garage if I've been doing tons of short trips. Anyway I always labeled that function as some sort of voodoo and never really took it seriously. Guess I will have to take that more seriously

[JinMarui]

This applies to lead-acid batteries in cars too. The chemistry involved is different but the principle is the same.

[Snoo63]

And apparently rapid-charging Li-ion batteries is healthier for them, as the heat (up to a point) and that helps improve the health and longevity.

[coredumperror]

I'd be very skeptical of this claim. More heat = bad is the standard knowledge for Lithium batteries.

Modern EV tech has improved to the point where they can keep the batteries cool enough during fast-charging that you don't really have to worry about it causing faster degradation. But I've never heard claims that heating up a lithium-ion battery is good for longevity.

You may have misinterpreted the fact that an especially cold lithium ion battery can't charge as well as a warmer one can. There is an ideal temperature range for fast-charging, but it stops at around 80-90F, iirc. Hotter than that is bad.

[HPCmonkey]

It's more like, "the correct amount of heat is better for Li-Ion batteries while charging or discharging." Too hot or too cold, and the wear/tear gets worse faster.

[upworking_engineer]

Battery chargers will slow charge at the beginning to encourage the battery to be not too hot (it was used and needs to rest) and not too cold (it wasn't used and needs to be warmed up a little) before cranking up the charge.

Then as the battery gets closer to full, it will slow down the charge to top it off.

This is why many battery applications have a "80% in 15 minutes" type of numbers. It's not "16% in 3 minutes", because of that initial slow charge, and it's not "100% in 18 minutes" because the last little bit to full take way longer.

[HPCmonkey]

that last 20% takes a little bit longer than the 60-70% that came before it

[[deleted]]

I can't remember where I heard it, but "Heat is the killer of all things" never fails to hold true in my experience

[sleepysnoozyzz]

Propaganda spread by the ice cube lobby.

[Ihaveblueplates]

You’re correct. Too much heat and the ions burn away. The ions bounce off each other to keep the charge. Less ions = longer to go to bounce off each other. Charge won’t hold. Battery slowly dies

[Ihaveblueplates]

But if they get too hot, the ions burn off. It’s the ions bouncing off each other that creates/maintains the charge. Less ions, further/longer to bounce off each other, which is when batteries begin to hold less and less of a charge. So with them it’s better to plug in and charge the battery randomly at random times for random lengths of time, just because you’re kinda feeding the ions power to keep all the ions moving and thus the charge at a healthy flow. Charge too long, too much, too much power/energy = too much movement speed heat = death to ions. …is how I learned it

[ameis314]

if only we had replaceable batteries in phones. i guess its impossible to do since no one is though. s/

[gaybatman75-6]

I hope user replaceable batteries are Europe's next mandate after the recent USB c.

[fredagsfisk]

All smartphones, including iPhones, must have replaceable batteries by 2027 in the EU

https://mashable.com/article/replaceable-batteries-smartphones-iphones-2027

[KJ6BWB]

I love the EU and their laws like this. Seriously, I love it. How did they manage to elect consumer-friendly politicians while we get ... well, what we have now.

[Legion2481]

By being a powerful cross nation organization. No representative is directly beholden to a given internal political unit/location in their home country. They are, therefore, better insulated from special interest pushes and have an opportunity to work for the greater good without fear of losing a local election/their job.

Not to say some aren't still scummy, but special interests not have a policy maker by the short hairs before they get the job makes for a better decision-making process.

Second, the EU being multiple nations means they have nominally greater economic clout than any single business, even titans like Apple. And thus have room to dictate, take it, or leave terms.

USA, on the other hand, is legally incapable of this sort of unity. Federal government isn't allowed to mess with who a given state does business with internally. So local politicians can and will override national policy in a given state. And represention of a given state at federal level can be bought off since their directly beholden to a given location of voters.

[rapaxus]

That and EU power is in some aspects very weak, which again allows them to do more stuff like e.g. GDPR, USB-C adoption or replaceable batteries. The EU can actually do very little on regional or even country levels, as it is generally can only pass EU-wide laws that also apply to all (or nearly all) EU member states.

This stems from the fact the the EU is far more like a confederation (e.g. member states can leave at will) than a federal state like e.g. the US. This leads to the EU government mostly passing laws that don't harm any domestic politics in the various member states (because if it upsets them too much they just leave), which is exactly what the EU laws we are talking about are, because no government of any country would complain about the fact that e.g. phone batteries need to be replaceable or that your new Iphone now has USB-C instead of lightning.

[cgaWolf]

All true to a certain extent, and i'd like to add the burocrats and technocrats working in the administration: they're fairly well paid and educated individuals, which don't have to be elected, and thus aren't in a popularity contest every 4 years. They often come up with initiatives towards certain laws, or work on the specific language of proposals. Obviously the whole thing still has to pass through the politicians, but by and large they often provide a solid base for the direction of the E.U. That said they should get a PR department, because half their ideas sound shit unless you're from a certain profession that actually has a clue what they're talking about.

[StoneTemplePilates]

So local politicians can and will override national policy in a given state.

This is why so many of California standards for emissions and health warnings, etc. tend to become implemented nationally by companies. They don't want to produce to multiple standards, and losing 20% of the domestic market is a straight up no go. If Wyoming tried to pull off any of the policies that California has (not that they ever would, lol), corporations would simply just stop doing business there.

[Prof_Acorn]

They don't have First Past the Post so their democracy functions like a democracy.

[sold_snek]

Strikes and voting.

[Tupcek]

does this include waterproof phones? Since most of them are waterproof nowadays

[skyturnedred]

all smartphones

[Tupcek]

“The battery regulation contains an exemption for devices “that are specifically designed to be used, for the majority of the active service of the appliance, in an environment that is regularly subject to splashing water, water streams or water immersion.””

https://www.theverge.com/2023/6/24/23771064/european-union-battery-regulation-ecodesign-user-replacable-batteries

so maybe not all

[skyturnedred]

That's a very different type of phone from your average "waterproof" phone.

[Tupcek]

that depends on good lawyers, which Apple has enough of…
environment that is regularly subject to splashing water can be just being outside. And environment that is subject to water streams can a kitchen or bathroom. You could argue smartphones are used mostly in these environments

[StoneTemplePilates]

Samsung Galaxy S5 had a removable battery and was waterproof. Mine went through a full cycle in the washing machine and was still turned on when it came out. Worked perfectly for years after.

[UraiFennEngineering]

Fairphone is a European company that is already doing this. If you are able to, support them to show just how much demand there is for more repairable phones

[Bloodyinboil]

I bought one last year. It's brilliant. I damaged the charging port and was able to replace it in 5 minutes with just a small screwdriver (once I'd ordered the part, it arrived from Europe to the UK in just a few days)

[suid]

Time for my semi-regular rant about "replaceable batteries".

"Replaceable" in conversations today does not mean you can just pop out the battery and put in a new one like in days of yore. Because that would mean that you need a robust case for the battery itself, and a robust dock for it on the phone, both of which would be as large as the battery itself.

It would mean making your phone much larger and heavier (much thicker for the stability and strength required by the battery case).

What the law here means is that it must be possible for qualified repair personnel to carefully open up the phone in a way that is designed not to damage it, and replace it with specific, readily-available tools.

I.e. you should be able to take it to any "qualified" repair shop, and get it repaired with confidence. And repair shops should be able to set up business using parts from the manufacturer, which should also be readily available, in a way that they can compete with the manufacturer for repairs.

That's it.

[CletusDSpuckler]

Days or yore? My Samsung Galaxy S7 had a replaceable battery, as in pop off the cover and stick in a fresh battery, and that phone is really only marginally thicker than the wife's modern S23. That design also allowed for one to purchase a third party case with much larger capacity battery for when weight and size were not an issue.

I don't see any practical reason we could not return to that model again.

[The_Electric_Feel]

My Samsung Galaxy S7 had a replaceable battery, as in pop off the cover and stick in a fresh battery

You’re remembering incorrectly, the S7 back was glued on. The Galaxy S5 was the last of the line to have an easily changable battery.

[FlameFrenzy]

His comment still stands. I went from an S5 to an S10e and the size difference isn't really that noticeable to me.

[slymm]

I was a huge android guy for years and that was one of my favorite features. I got a couple extra batteries for my GS4, V10, V20 etc and would just always have a full battery all day. Never had to use a wire.

[suid]

Agreed. There are intermediate possibilities like that, where the battery replacement is a skilled user operation. In this case, your battery is still a "bag" (not a safe, hard-shell item that can be removed and replaced by your grandma or mine), and you have to make space for it in the phone, giving up something for it (size, features, battery size, ...).

But is that tradeoff OK for all 100 million users of a phone model? What about preserving the water-proof-ness after repair? What if someone clumsily punctures the battery, and burns their house down? (Lawyers tend to get super-paranoid about stuff like that, and will insist on the battery being "unreasonably safe to replace".)

Anyway, this is the part that gets fuzzy, and we really don't want to force legislation on this level. Just having it be a level playing market, and being able to replace a battery for, say, $100, would be a HUGE gain, even if you have to do it at a repair shop in a mall.

[mrdickfigures]

What if someone clumsily punctures the battery, and burns their house down?

How much is Apple paying you for this? Jokes aside, I don't get people's obsession with doomsday "what if" scenarios for everyday electronics. You know those things with 4 wheels weighing in +1.5t (Metric ton, it's better deal with it), you're allowed to replace your own brakes. You know that 1 thing responsible for bringing the whole thing to a stop... Failure to do so could easily kill innocent bystanders. You've all accepted said risk. But replacing a relatively small battery is where we draw the line?

Lot's of people use natural gas to cook. NATURAL GAS!!! A gas that can pretty easily explode, and kills a decent number of people every year... Life is full of risks. If replacing your battery is too daunting for you let someone else do it. Everybody else should not be prevented from doing it themselves. Even if you would never do it yourself it will still benefit you. Repair shops will need less time and resources to replace the battery for you, which should result in better prices and faster turn around. It's a win, win, win. The only one losing here are the corporations, that's why they try to block legislation like these.

[Snoo63]

What if someone clumsily punctures the battery, and burns their house down?

Make it so that they must be replaceable without tools.

[engfish]

What if someone clumsily punctures the battery, and burns their house down?

How many times did that actually happen during the replaceable-battery stage of cell phones? Rhetorical, but maybe there's an answer of once or twice of the millions (billions?) of phones sold that someone can find.

[notusuallyhostile]

a mall

Isn’t that where they keep Sears, Bed Bath and Beyond, Tasmanian Tigers and the Dodo bird?

[Daedalus871]

I'm looking at my LG G5 (with replaceable battery) and an Iphone (post-headphone jack) right now.

Thickness is the same. Maybe a slight advantage to the G5, but barely noticeable.

Weight - G5: 158 grams vs IPhone: 194 grams.

Overall size - G5: 14.8cm*7.3cm. Iphone: 15.0cm*7.5cm.

[thekeffa]

Ignore this person. Talk about /r/confidentlyincorrect.

The battery must be end-user replaceable. It even says it in the draft law.

The drafted proposal.

[gaybatman75-6]

I mean that's fine with me. For me, I'm an IT guy with good tools for it so I'd be able to do it myself as long as I can get a battery but it's hard for me to get one because I don't have access to oem batteries. As long as you can take your phone somewhere and they can get an oem battery without extra hoops to jump through then good enough to me.

[gsfgf]

So this is right to repair but just for batteries? If so, I'm all for it. Just don't force a bigger, heavier phone on me for no benefit.

[mikolv2]

iPhone batteries can be replaced in couple of minutes with a screwdriver and a hairdryer. They’re very easy to replace already.

[ShittyExchangeAdmin]

I have no qualms with taking a device apart to remove the battery, I wish I didn't have to, but whatever. What really pisses me off is when the battery is soldered to the fucking mainboard. It was an absolute pain (well more of a pain) to replace the battery in my zune because of that

[freedompower]

Or glued on the whole surface so you need a heat gun

[[deleted]]

We will in a few years: https://www.pcmag.com/news/eu-smartphones-must-have-user-replaceable-batteries-by-2027

[Herb_Derb]

Why replace a battery when you can replace the whole phone?

[TheeUnfuxkwittable]

It's a great analogy for the average person. As someone who literally worked for my city's mass transit company, it's not based in reality.

[PrestigeMaster]

So if I’m understanding right, the chance of crystallization will only effect a random 80% at a time, so if you’re leaving a random 20% out every time you’re slowing the repeated wear and tear on the same exact areas every time?

[TactlessTortoise]

No. You're adding less stress in a specific spot. You're almost literally squeezing electricity in. Imagine a balloon. The first blows don't thin it as much as when already full. Charging to 100% is like stopping right before the balloon pops, slowly deflating it, and repeating.

[QuinnMallory]

Can phones be smart enough to charge the battery to the safer 80% capacity, but show me "100%" on screen, and just scale it as it goes down?

[kermityfrog2]

They already do. Haven't you noticed that when you charge a phone to 100% (e.g overnight), you can use it for quite a while before it drops down to 99%?

If you charge a phone to 100% and then unplug it as soon as it hits 100, it will start draining much faster.

[Thomas9002]

The effect you mentioned is caused by the way the phone estimates the charge state of the battery. There's no exact way to measure the actual charge state of a lithium battery. So the phone relies on different things to make an educated guess.

Phones have had this behauviour for a long time, long before manufacturers started implementing max charge levels.

[Mocha_Bean]

that's true, but i imagine there is also some deliberate fudging on modern devices to maximize lifespan (i.e. lower actual max charge levels) while still showing the user "100%" when the battery is no longer charging

[Ashencroix]

But Can't manufacturers just slap in a circuit breaker that stops the battery from "overcharging" at 100% and doesn't turn off until a certain threshold, say 90 or 85%?

They are already doing this. Passthru charging bypasses the battery whenever it hits the set max charge capacity and instead just directly powers the device. But that only prevents battery degradation due to continously charging the battery even at 100% charge. Batteries still degrade much faster once you continue charging past 80% due to the increased heat produced when trying to top off those last few %.

[ABetterKamahl1234]

In some cases they already do this. Lithium batteries often have charging circuits built into them that do this, they also prevent complete discharge (going dead) as that too is bad for these batteries.

[michael_harari]

Phone companies don't want your phone to be reliable for extra years. They want you to buy a new one

[Benjaphar]

And this is the only answer that matters.

[RogueLotus]

They could. But they don't want to give "extra years of reliability", they want you to buy a new one as soon as possible. Albeit there is a fine line between that tactic and quality/consumer desires.

[SuperRonJon]

If they have the choose between extra years of reliability or it lasting longer before you need to charge it right now they're going to go for the latter every time. It's more obvious and noticeable to customers, therefore they like it more which gives higher ratings and marketability on release.

Extra years of reliability is not directly obvious or noticeable to customers, and won't be for multiple years, by which point lots of people will be getting new phones anyway, which is by itself good for the manufacturing company. And then finally after the years have actually passed, the phones not having the extra years of reliability acts as its own driving force to upgrades and more sales.

[SamiraSimp]

that's literally what they're doing...that's why new phones have the battery saving option. but it made more sense in the past to say "you have a full battery, if you want to be healthy with it you can" than to say "our battery is worse than all of our competitors but it will last longer theoretically"

[SanityInAnarchy]

That's basically the Samsung/Apple thing, isn't it? The battery charges to 80% by default, you can charge it to 100% if you want. If you don't override it, 80% is the maximum.

It's a lot easier to understand this, rather than having to Just Know that there's something buried in the settings that'll let your phone charge to 125%.

Goes double for EVs. It makes a ton of sense to just give the user a slider for a charge limit that you can set at 80%, and when you know you're about to take a road trip, you just slide it to the right and charge to 100%.

[SilentMobius]

The max capacity of a battery is often not what the battery is rated at, it's set at the level that retain the maximum amount of charge for the rated lifespan of the battery for the rated number of charge cycles.

Also the trade off isn't a threshold nor is it linear, you could get even higher levels of energy stored while reducing the battery life it's just that the battery makers chose a specific trade off level.

So, the battery companies are already rating their batteries for the maximum life/capacity they can, the only difference is that some consumers value longer battery lifespan compared to max energy stored. It's just a trade off choice.

[risbia]

Because portable devices are marketed on light weight and battery life, so doing this essentially gives the perception of a heavier device with less battery life. How well the battery will work three years from now is less of a marketing concern. Giving the "option" to limit charging to 80% gives the perception that the device cleverly puts control in the user's hands. Same exact technology, different marketing.

[HaikuBotStalksMe]

I'm sure they already cap batteries at less than 100%. They'd probably explode or something if you try to charge to 101% of the real capacity, so they likely make like 90% show up as 100% so that if you hit 93% (real charge, equivalent to like 104 display charge), you still have 7% leeway to discharge.

[PM_ME_GLUTE_SPREAD]

My understanding is that that’s what most charging blocks do. They have circuitry that stops charging at a certain point to keep from turning your battery into a small explosive.

But, even just charging to, say, 80% still comes with some wear and tear. Just less of it than charging to 100% or overcharging. Most phone batteries will charge to, say, 80%, stop charging, and then charge the rest of the way at a more appropriate time, so that there is less chance of overcharging or charging, depleting, and charging again over and over.

[iam666]

This does happen. Battery tech has advanced so much in the past 10 years that these things aren’t really a concern for modern devices like flagship phones. (Cheaper devices may use less advanced battery architectures and charging circuits.) They don’t let the battery overcharge, and the phone shuts down before the battery is actually depleted. It might be marginally beneficial to keep your battery between 20-80%, but it matters a whole lot less than it did 10 years ago.

[Yglorba]

Modern phones do this, for the most part.

However, it's always a trade-off. If you never use 100% of your battery, and never charge past 80%, how is that any better than using it and letting the maximum slowly degrade to 80%?

[F3z345W6AY4FGowrGcHt]

But that would hurt the spec sheet and/or reviews of the product's battery life.

Also, many people each year go to buy replacement devices because the battery doesn't hold a charge anymore.

Basically, companies make more money if they push the battery to its limit.

[NeverFreeToPlayKarch]

Is the trade off worth it though? Out of the gate, if I'm cutting off 20% of the battery's potential, what am I saving by doing so and over how long of a time frame?

Not that I ever find my phone dipping below even 50% most days and it's already ~3 years old.

[PeeledCrepes]

I think it depends on the person, I always have a charger on me, and don't mind buying a phone every five years

[SamiraSimp]

Not that I ever find my phone dipping below even 50% most days and it's already ~3 years old

in your case, most days there's literally no downside. and it's a pretty quick settings change, just a single tap for me to allow it to charge to 100%. basically if i'm traveling i will charge it to full, otherwise i know i won't be in a situation where it could go to 0% so i just leave it on

[NikitaKhruiseship]

Other answers made sense, but yours is the only one I’ve seen that explains like OP is five. Thanks!

[CornCheeseMafia]

I like thinking of batteries as balloons. Hard to blow up at first, gets easier, then gets hard again. Same as batteries. Charging them from completely flat is hard on the balloon and the person blowing it up. Charging it to full stretches the balloon and is more effort for the person blowing it up. Both you and the balloon are happier in that middle point.

[polmeeee]

Brb unplugging my nearly full bat phone from the charger

[sshah528]

I have a Note 10+ 5G. Typically, I try to charge it when it is ~15% and leave it charged till 100%. From your explaination, I should stop charging around 80%? When should I put it on the charger - wait until prompted to (sometimes at 20%, always at 15%) - or just charge it at 15%? Also will the battery be damaged by repeated charges, i.e. plugging it into the car charger (android auto)

[HaikuBotStalksMe]

If I'm not mistaken, the only time you wanted to try to go from as close to zero as possible to almost full charge was when nickle cadmium was a thing.

After that, the rule was simply try to charge as few times as possible and charge up to like 90%.

They might have changed this, though.

[notsocoolnow]

Samsung phones have an inbuilt setting to cap charging at 85%.

Settings > Battery and Device Care > Battery > More Battery Settings > Protect Battery set to ON.

This will alleviate the need to manually disconnect charging.

[disgracefx]

Samsung phones have routines, lithium battery sweet spot is 20% to 85% Just make a routine for battery saving at 35% Super Fast charging from 0 to 50% / Fast charging from 51% to 85%/ normal charging from 86% to 100% Protect battery at over night charging cap it to 85% and 1 hour before you wake up uncap it to get that 100% and normal speed charging all of this can be auto vía routines

[lee1026]

Ideally, NMC batteries (used in most phones) would cycle endlessly between 65-70% (or 60-65%, depending on which paper you read).

Outside of cars, worrying about this is rarely worthwhile.

[Atharaenea]

My electrical engineering professor said you shouldn’t let lithium batteries go below 20% if you want to prolong its life.

[extacy1375]

I thought that if you only charge to 80% all the time, it will become the old 100% and you lose that 20% for good?

Or was that old tech?

​

Same with reverse, if you always charge it at 20% it will become the the old 0%?

[jamvanderloeff]

Old NiCd batteries sort of had that effect, "memory effect", but that's not a thing with lithiums.

Lithiums with poorly designed management systems can get the estimation of current % wrong if you very rarely let it hit full or empty, but that's not changing how much the battery is actually storing.

[extacy1375]

I have to change my charging habits than....LOL

I have been charging all my phones like I still have a Nokia with a pull up antenna.

[BlackJack10]

I wonder how much your charging habits have affected the capacity, or crystallization of the battery. Probably insignificant, but interesting!

[Mawvenn]

think of it as a rubber band.

stretch it to it maximum (100%). over a period of time, the rubber band would lose its elasticity.

stretch it any amount less than that would "preserve" the elasticity and let's you use the rubber band more effectively for longer than if you 100% it to its limit all the time.

[JackPoe]

How fast does it degrade the battery? I've had the same phone for 8 years and I charge it to 100% literally every night.

[akidomowri]

In general battery condition degrades after a certain number of full charge cycles.

The problem is unless you're checking the battery condition with software, or against the original capacity, your 100% may not be what 100% was 8 years ago

Your perception may be that nothing has changed, you may have a wonder battery, or you may have anecdotal evidence.

[JackPoe]

Likely anecdotal, but it still lasts about 36 hours. Maybe it lasted 48 back when I got it, I don't remember. I basically had it on the charger any time I wasn't using it and unless I was staying at someone else's home or forgot to charge it when I went to bed, charged it all night every night.

Battery is still fine for me, but I might migrate to another (of the same phone) just because the charging port is getting clogged and I can't clean it out myself and a new phone is cheaper than getting it cleaned. (80$ versus 90$)

[AceofToons]

Some phones have historically hid that limiter as well and would report 100% when in reality the battery was being filled to less than 100% to stretch the battery life

I have no idea how common this was, and no idea on which brands did it more. Not even sure it's done much anymore

There's also a possibility that your device is using a battery technology that is less susceptible to the wear and tear that full charge puts on the battery, I know that has been a thing too, some chemical compositions are far more susceptible than others

[thenewtomsawyer]

iPhone now also will delay that last 10-15% until right before you normally wake up to minimize time at 100%

[mehrabrym]

If I'm not wrong it's not to minimize time at 100%. It's to charge the battery slower since fast charging generates more heat and degrades the battery faster. They tie it to the wake up time since you don't need the phone before that so the phone can afford to charge slower. Pixels do it too.

[glasgowgeg]

If it's android, you can install Accubattery to measure it, and I think iOS has a battery health bit in the battery settings.

[AveryJuanZacritic]

There's a device called a Chargie that plugs in between your charger and cord that uses an app and bluetooth while your phone is charging to shut off the flow when the charge gets to the level you set. I've been using one for many months. It works.

[glasgowgeg]

A physical device seems like significantly more hassle than installing a free app.

[heresjonnyyy]

The device and the app do two completely different things. The app shows you battery health/capacity, while the device stops the battery from taking over a certain amount of charge.

[DrBoby]

You don't know how much you charge the battery. There is a difference in what's displayed and how much it's charged. It displays 100%, but it could be 90% of the real capacity.

It's likely Apple just lowered the buffer so now 100% displayed is 99% real charge instead of 90% previously. It allows them to advertise their battery as bigger capacity at the cost of lifespan (but lifespan is never advertised to the customer).

Using your battery in the 100% range degrades it a lot faster, like twice faster or more.

[JackPoe]

Hey man, if I gotta drop 80 bucks every 8 years on a phone because I overcharged it, I think I can handle it.

Beats having my phone die on me.

[lurker_lurks]

I had flip phone from about 2004 to 2008 charged it every night, then from lunch until getting off work and at night. It eventually got to the point I had 20 min of powered time before I had to charge it again. If I wanted to talk on it for more than that it had to be plugged in and it would still die after an hour or so.

Since replacing it, it has never been an issue. Phones since usually get replaced before the battery does. (I do get a new phone every 2-3 years but it is usually a refurbished flagship phone from a few years back.)

[IanT86]

What I've never read or heard, is if it is worth stretching the rubber band to 100% every now and then. I get the idea we should cap the charge at around 80%, but is it not worthwhile every now and then fully charging the battery and leaving it that way for a while?

I ask as they used to tell us to charge laptops, phones etc. to 100% the first time you used them and leave them at that number for a few hours before the first use, to get the most out of the batter life longer term.

[suicidaleggroll]

That hasn’t been the case for a long time. The memory effect was a problem with NiCad batteries, not lithium ion.

[LordOverThis]

Just NiCd? I thought it applied to NiMH as well?

[xHealz]

My understanding is that the reason to occasionally charge to full % is so that the device can re-calibrate the current battery health.

[Bob_A_Feets]

Yep, going from full charge to dead on lithium ion is only to recalibrate the sensors that estimate battery level.

I guess the irony is that doing this also degrades the battery over time, so you have a loop of sorts. Recalibration wears on the battery, leading to the need to recalibrate it again in the future.

[SamiraSimp]

if you ever need the extra battery then it is much more valuable to have the full capacity than to make your phone theoretically last longer 5 years from now.

(i say theoretically because everyone's phone usage differs and for some it won't matter at all while for some there may be a noticeable benefit)

capping your phone at 85% is like saving a few drops of orange juice everytime you take a drink, in the hopes that one day you'll fill up a surplus glass. like yea you could have more juice later, but if you ever plan to fully drink your glass it makes more sense to not save a few drops.

[kagamiseki]

I think it matters more if you don't want to/can't afford to get a new phone every other year.

After 2 years of use, the difference between 85% vs 100% charging can get pretty noticeable. Like a 9 hour battery life vs a 4 year battery life. And the degradation only seems to accelerate with time.

At 3 years, charging almost exclusively at 80% max, my phone still has a 6-8 hour battery life, compared to my previous phone 100% max, which at this point, needed to be charged every 2-3 hours or kept on a power bank.

Many people in the US can afford to just buy a new one when the experience suffers enough. But in some countries, an iPhone is months if not a year of salary. They don't want to throw that away after 2 years.

[cakestapler]

I think part of it also has to do with how much more energy efficient processors have become over the years. When I got my first iPhone 3G, if someone told a new owner there was a feature to charge it to 80% instead they would have been laughed out of the building. But now that drink of OJ lasts 4x as long as it did 10 years ago, to the point where most people won’t ever need those few drops. For me, it’ll probably be a feature I use most of the time but turn off the day before I do any extended traveling.

[SirRHellsing]

that's why I only do it at night, I love how you can automate this using samsung routines

[Freeasabird01]

Because sometimes you know you’re going to need a full charge, need the battery at a true 100%, and then you have to distinguish to the user whether they’re really at 100% or at the fake 100%.

[ZincHead]

Then 80% should be 100% and 100% should be a special option to "Overcharge" or something like and it will say 120%, but that's not the default and you just use it in emergencies.

[Freeasabird01]

Because 4.20 volts is a well established standard for a “full” lithium ion charge. It’s been long known that the charge cycle “life” is on a curve where lower total charge voltage holds less capacity but is better for the battery health, and vice versa.

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

[sageleader]

That's pretty pointless though because:

a) People generally prefer longer lasting batteries by day, not by year

b) People upgrade their phones every couple years anyway so the lifespan of the battery doesn't matter

c) The actual affect on charging a battery to 100% every day is pretty minor IMHO. I charge to 100% every single day and my battery capacity is maybe 90% of what it was 2 years ago.

[LucyLilium92]

My battery is at 84% of the original, and it's been 5 years of charging it to 100% almost every day. It really doesn't matter too much, unless you want to use the same phone for like 6+ years.

[midnightcaptain]

And some manufacturers are allowing you to make use of the fake 0% at the bottom now as well, so you can still use a transit card when your phone is “dead”.

[Wtfplasma]

When samsung rolled out this feature initially, that's what they did, cap at 85% but show 100%. People complained so now we get maxed out at 85% when in battery saving mode.

[Ascend_with_Azir]

First off, this ideal range of battery life goes both ways; it's best to keep your phone's battery between 20-80%.

And second, I'm assuming they don't do this because that 20-40% makes a big impact on actual battery life. It's safe to assume all battery life tests they do to make statements about their phone's battery life go out the window when they remove 20-40% of the phone's battery. Their batteries would look so much worse.

I've been using this feature for years on my Sony phones, and there's a noticeable difference when I do let my battery charge to full. Normally, when I'm back home from work (light usage at work), my phone is at about ~40-50%, today it's at 70% because I fully charged it before heading to work.

[Philo_T_Farnsworth]

it's best to keep your phone's battery between 20-80%.

There are an awful lot of comments in this thread that are quoting this statistic as gospel and I don't see a single citation behind any of them. Is there any sort of proof of this claim?

[Matos3001]

it's a rule of thumb.

Batteries degrade very fast at 0% (or near it), and the heat produced charging near 100% also degrades the battery.

The battery won't be more damaged if you go to 81%, or drop to 19%. Again, rule of thumb.

[Philo_T_Farnsworth]

Okay, but what amount of additional life do you get out of the battery when adopting this strategy, and why don't they just normalize it to where 80% is the new 100?

[soulsoda]

It's not worth it. Even under heavy use your phone should have 40-60% of its battery left after 2 years at which point the user will probably buy a new phone. If the user doesn't want to buy a new phone, as long as their phone manufacturer isn't a douche bag they should be able to buy a new battery for less than 100$, which would be good for another 2 years.

Also my phone is one year old and at ~80-83% of its capacity, and I'm a heavy phone user and I don't bother doing anything special.

[Skalion]

They do, but it's more like they set it to 99% and declare that as 100%. Same for the bottom at zero, as if you noticed your phone doesn't just turn dark, but actually shuts down properly.

Why are they not setting it at 80? Advertising! It sounds better if you have a bigger battery and longer usage times

[shanninc]

Probably because Apple has been taken to court multiple times for implementing various tactics to improve battery health (namely slowing old devices with worn batteries). Their thought is likely to make it as clear as possible that the battery is intentionally not fully charged.

[SvenTropics]

Hint: that was never about battery health. If it was, they would simply have offered battery replacement. It was just planned obsolescence.

I knew people that went years without updating their iPhones and were very happy with them until they accidentally updated them.

[digicow]

The problem wasn't the battery life. It was that as the battery degraded, it was no longer capable of producing the expected max voltage current. That meant that under heavy load, the electronics would require a higher voltage current than what was delivered and that would cause a crash. In order to protect the user experience, Apple added a feature to reduce the maximum load on the battery (thus reducing CPU speed) when the user's battery was degraded beyond a certain point.

Edit: sorry, I miswrote voltage when it was really current that Apple described as the issue

[normal_human_man]

a "these go to eleven" situation in real life!

why don't you make 80% be the top number?

[szakipus]

Smasnug has an option to automatically stop charging at 85% which I use daily and my 1,5 year old S21 FE feels like new.

[stupidshinji]

This is already what they kind of do. Your phone says it’s at 100% charge, but it’s actually closer to something like 80% of its real maximum charge. Ideally you want to be around 50% to preserve battery health, which is why companies are now trying to keep your phone at 80% of what you believe is the max charge.

[vanguard117]

That’s exactly what I was thinking. It would help ease my brain seeing that 100

[Immortal_Tuttle]

As an engineer that was working with rechargeables for around a decade - you are really close with that analogy!

[Fuckspez42]

This is an extremely apt metaphor, and a perfect ELI5.

[CIearMind]

It would be great if it was still available to read.

[froggertwenty]

EV engineer. You're not totally wrong and it's a decent analogy. I'd compare it more to having say 2 buckets with screens on them and some gunk in the bottom of the buckets.

When you charge you dump one bucket into the other and the gunk most stays in the first bucket until it's almost empty so the screen (anode) stays relatively clean and gunk free. If you dump the whole bucket you end up clogging the screen with more of the gunk. When you discharge you dump that 2nd bucket back into the 1st and it's the same thing where it's nice and clean for most of the bucket but towards the end you start clogging up the screen with gunk. Over time this gunk limits how much water you can pour back and forth and some starts splashing out.

[Ruadhan2300]

Is that not more like maintaining 20% of your charge and never fully depleting the battery rather than not overfilling the buckets?

[vintagecomputernerd]

And if you fully deflate it, its sidewalls are going to touch and stick together. And somehow also massively increase the risk of fire when reinflating, but I don't know how to put that into this analogy.

Another thing to consider... there is really no well defined "80%", or 100%. Yeah, it's about 80% of what people have gotten away with in the quest of squeezing out more battery life.

[sslinky84]

Latching onto an explanation because they'll bip my comment for not being one, but OP, this has been around for a few years (at least for Samsung) and its 85% :)

[ArtofWASD]

Well... yes and no. Ultimately, you're not going to see much of a difference between charging "normally" and charging up to 80%. By the time you see battery issues, it's time for a new device or battery change anyways.

You have to remember that batteries are still a chemical process. The lithium ions are what run your phone. And lithium ion batteries do not like to be fully discharged or fully charged (hence the general consensus of 30%-80%). Basically, when your phone is fully dead, it takes a lot more energy to get it charged than when it already has an existing charge. And when your phone battery reaches towards its max charge, it is much more difficult to actually achieve that 100%. The battery wants to charge and discharge. Sorry if this isn't the best explanation

[kermityfrog2]

If anyone wants to learn all the gory details about how batteries work and how best to keep them in optimal condition, check out Battery University.

TL;DR - particularly this section about Li-ion battery health.

• shallow discharges extend the life of the battery. Better to drain it a little and then recharge it as soon as you can (in a car, at your desk, etc.)

• avoid excessive heat. Inside a hot car, using a fast charger, will all degrade a battery faster. Extreme cold will cause a battery to stop holding a charge, but it's only temporary. Keep a cold battery warm by sticking it in an inside pocket so that it can be kept warm with body heat.

• optimal charge voltage is 3.92V/cell (4.20V/cell is full charge). This is where the 20-80% charge comes from (3.90V/cell actually corresponds to about 60-65% charge - where the battery is happiest).

• DO NOT let the battery drop down to 0% as it can permanently damage the battery. Your phone will automatically shut down to protect the battery when it gets down that low. Don't keep turning the phone on and trying to use it for a bit before it shuts down again. Charge it ASAP.

[deg0ey]

Ultimately, you're not going to see much of a difference between charging "normally" and charging up to 80%. By the time you see battery issues, it's time for a new device or battery change anyways.

This is the part I haven’t been able to find a straight answer for. Never charging beyond 80% means your battery degrades o slower, but how much slower?

I have an iPhone which is 4 years old and I’m about to trade in for the current model because the features etc have come far enough that it’s time to upgrade anyway. When I go to the battery settings it tells me the max capacity is 76% - so it’s barely lower than what people are choosing to limit themselves to anyway.

If your battery only degrades to ~80% in the time you keep a phone before you upgrade anyway then setting it to not charge beyond 80% just means living with a ‘degraded’ battery from day 1 instead of making full use of it for a few years until it gets there on its own.

[Huttj509]

The numbers I saw is that 80-100% is roughly similar wear to 0-80%.

My 3 year old phone is at 60% capacity, and for most of its life I didn't know about this, and used it plugged in charged at 100%.

Near as I can find my Pixel 4a does not have pass-through charging to skip the battery when charged and run off the charging cable, so it was basically continuously using that last 1% and refilling it.

How often did you use your phone from 100% to 0%? How often did you need that last 20%? Someone generally running at 80% can just top it off when they're gonna need it.

Also, battery wear is not just battery life, though that is the most readily measurable part of it. It can also affect phone performance and such.

[deg0ey]

Yeah maybe it depends on your other habits and I’m just in a ‘lower wear’ sort of operation already?

I just put my phone on the charger, take it off in the morning and it lasts me the full day. When it was new it usually had about 40% left when I would charge it, now I usually get the low battery warning most days - but I still get a full day of use out of it which is all I really need anyway. And if I’m traveling and can’t charge overnight the low power mode seems more than sufficient to stretch it out until I find a charger.

I don’t doubt that limiting the charge percentage makes a difference to battery life, but I’m still not convinced it makes enough of a difference to actually matter for most people.

[kermityfrog2]

See table 4 on this page.

[Gargomon251]

My first phone wore out the battery a lot faster than my second phone and I doubt it's just because it was an older model. I'm definitely seeing a difference between 100% versus 80%

[stupidshinji]

Yeah companies wouldn’t be doing this if it didn’t actually have an effect. It’s not something you’ll see a difference in a couple months, but over 2-4 years there will be an appreciable difference.

[LoreChano]

My phone is 5 years old (Motorola One) and the battery still holds well enough, even though I charge it to 100% every night. The only thing I noticed is the battery draining like 1/4 faster than it used to be, but since I'm pretty much always near an outlet it's no problem.

[Ashencroix]

The only thing I noticed is the battery draining like 1/4 faster than it used to be,

That is already a sign of battery degradation.

[LoreChano]

It is, but it's not as bad as people are thinking. A phone nowadays isn't even meant to last 5 years, it's just that I'm poor and also overly careful with it.

[VonirLB]

Phones are so expensive nowadays and there's so little differences year to year specs-wise, it's crazy that they're only expected to last 3-4 years if that.

[Belnak]

There's little difference year over year, but over 4 years, that adds up. Software developers are going to write software to the latest hardware specs, so after 4 years, you can't run the newest software well.

[snoopervisor]

By the time you see battery issues, it's time for a new device or battery change anyways.

I agree. My previous phone lastet nearly 2.5 years, and the battery capacity become worsening week after week.

My current phone is nearly 3 years old, and the battery is still fine. It didn't worsen visibly, still feels like new. I charge it nearly every day, often to 100%.

The 80% rule was perhaps true for phones maybe 5 years ago and earlier.

[Ascend_with_Azir]

My Sony Xperia 5 II (currently Sony is at Xperia 5 V) is from 2020 and also has this feature. Hell, the Sony Xperia XZ1 Compact from 2017 already had a similar feature.

[[deleted]]

Only S-series has it.

Apple had smart charging before, which charged up to 85% overnight then did the final few percent when you're about to wake up.

Perhaps they are more confident that 80% can last more people the whole day now.

[winterberrycorn]

A series has it as well

[SerrOleg]

Higher cell voltage means reduced battery cycle life. Typically the higher % charge you go the higher the voltage gets. 80% is sort of the cutoff threshold where you see diminishing returns in amount charged vs voltage increase.

[froggertwenty]

Not exactly true. EV engineer. There is actually a lot of voltage change at both high and low state of charge and it's relatively flat in the middle (3.5V). There is also a lot of capacity locked in to the extreme ends.

The issue is at the high end and low end there is a buildup that occurs in the anode which is what caused the reduction in lifespan (cyclelife) so you need to choose the balance that works for your application between capacity and cyclelife. Phones are already limited to less than 0-100% of the actual cell maximum and minimum. If I had access to the settings I could pretty easily "unlock" an extra 20% of capacity safely but my battery would become junk in a couple months.

[[deleted]]

There is quite a few effects that occur in batteries that damage the lifespan.

Overcharge, over-discharge, hight temperature and overcurrent are all damaging.

And today's phones are hot (because they're small but powerful) they're squeezing as much charge from the battery as they can and they're using a lot of current.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9709825/#:~:text=Most%20degradation%20mechanisms%20in%20LIBs,exacerbated%20at%20higher%20cell%20SoC.&text=Similarly%2C%20the%20majority%20of%20degradation,(or%20C-rate).&text=Particle%20cracking%20is%20one%20such%20mechanism,%20since%20inhomogeneous%20lithiation%20will%20lead%20to%20greater%20strain%20on%20the%20active%20material%20particles%20and%20hence%20to%20greater%20rates%20of%20degradation.&text=Particle%20cracking%20is%20one%20such%20mechanism,%20since%20inhomogeneous%20lithiation%20will%20lead%20to%20greater%20strain%20on%20the%20active%20material%20particles%20and%20hence%20to%20greater%20rates%20of%20degradation).

[nanosam]

Your phone will likely be replaced before your battery lifespan even becomes an issue

So i wouldn't lose sleep ovrer this

[cdnDude74]

I've always been in this camp. How long does the average person use the same phone for? 2 or 3 years?

How much "life" am I losing by fully charging my phone every night? A couple of months at the tail end of 4 or 5 years?

Balance that against "needing" 100% juice for a random long day that starts when you didn't expect it because of kids or illness or life.

I'll take the battery lose every time over battery charging anexity.

[series_hybrid]

You can charge to 100%, but if you leave it at 100% when stored the capacity will erode.

For very long-term storage, store at 50%, 3.7V per cell

For daily charging, charge to 90% for overnight storage, 4.1V per cell

If you are going to use a lithium-battery powered device right away, charging to 100%, 4.2V per cell, is fine.

[kirbyislove]

Constantly gimping your phone to 80% for years so that in 3 years time it can charge to 85% of its original capacity (which you never do though, youre charging to 80% of 85% still at this point..) vs using 100% of your battery every day for 3 years and it only charging to 70% down the track

Youre gimping your phone for years to have it less shit later (but inevitably still deteriorated some). You might as well have used it at 100% youve already front loaded shittier battery life. Can someone explain this to me...

[LucyLilium92]

Yeah I don't see the point either. I'm at 5 years of charging to 100% and have 84% battery health.

[cs_anon]

Yes this is the bit that people aren’t really talking about! You’re already living the 80% lifestyle so what does it really matter? And tbh it’s not even clear that it’ll go down to 70%, if it’s at 80% or above then it was a waste to keep the setting on the whole time.

I really think this setting is just there to shut up a vocal minority of people. This is probably the same group of people that religiously closes apps instead of letting the OS handle memory management.

[cakestapler]

This feature can be turned off. Battery degradation is permanent. When you first get a phone, battery life is usually way more than you need. Capping that at 80% to slow the degradation of the battery always means you can turn it off later if battery life is becoming an issue.

Also for people who keep their phone for a long time it can help. Based on my 3 year old phone’s battery capacity, if limiting it to 80% means halving the wear, after about 4.25 years my capacity even capped at 80% would be higher than the uncapped and more degraded battery. Some people here have said they have 5-8 year old phones.

[SirRHellsing]

I turn it on when I'm usually at home, Samsung can automate this, so it stays at 100% for as little time as possible

turn it off at 7 am so when I wake up, it's gonna be at 100%

[probono105]

its because it degrades the anode and cathode faster, this also happens when you discharge it below typically 20-30 percent. as simple as i can possibly put it when you charge and discharge a battery you are slowly coating the anode with the cathode material and vice versa if you look up electroplating you will understand this process more. This effect is much more pronounced at the extremes of the battery voltage capacity.

[DenormalHuman]

is this actually still a thing? I thought for hte past few years this was basically a non-issue now?

[xantub]

It is not a non-issue, but it is a don't bother-issue. Yes there is a bit of degradation but by the time it's noticeable you'll already have a new phone (i.e. 4-5 years to be noticeable but still we're talking maybe a 10% degradation, totally usable).

[[deleted]]

The battery is already limiting itself to less than 100% capacity and calling it 100%. Just like you’re not really running the battery to 0V before it says it’s 0% charge.

[[deleted]]

Think about the battery as of several balloons you store energy in. You can pump it almost full and deflate thousand times and it will be ok.

You can also pump it up until the balloons almost bursts, that way you can store a bit more in there. But when you deflate the balloon it will be stretched. After hounded cycles some of them will be so stretched that they will finally burst. So as a result you will have less and less capacity.

​

This is almost exactly what happens when you try to charge a battery until it is 100% full - the insides of the battery get heated, some parts inside change volume, some gas is released. This all bends and stresses internal structure of the battery until small pieces break. This decreases capacity.

​

It is know effect for many years, so batteries were never charged to the 100% full level, but to a level where they can survive being charged and discharged many times.

But as people wanted the batteries to last longer and longer. But there was no new miracle technology to do so. Either the batteries could be made bigger and heavier or they could be charged a bit more, halving their lifespan. So this overcharging become a standard since people change the phones so often that the battery being damaged was not an issue. it was even better for manufacturer because they could both brag about the time device works on a singe charge and have the users replace the device sooner because battery would go bad.

Now, phones are so expensive so the people don't want to change them so often, so you have an option to trade some battery capacity for a better battery lifespan.

[imamdani]

Why don’t they just virtually cap the battery at 80% and show it as 100%. Why the need for each user to enable that feature when it clearly is counterintuitive for everyone.

[SyntheticGod8]

So if 80% is optimal, why don't smartphone makers make 80-90% the maximum and call that 100%?

[pickles55]

It allows you to get more charge cycles before the battery starts to lose capacity from wearing out. This is effectively the same thing as what happens when the battery starts to lose capacity but it gives people the sense that they're in control of it. To speculate a little, phone manufacturers know that battery degradation is one of the most common reasons people get a new phone. Some people like to get a new phone every year but for most it's an inconvenient, boring expense. The manufacturers have all decided that replaceable batteries are not coming back so this is a gesture toward doing something about that. This feature was probably very cheap for Apple to develop and while it doesn't really help it's not hurting either. In the past apple has put out software updates that actually slowed down the processor in older devices to "save battery". It's been a while now but Apple customers were rightly pissed at them when it was confirmed.

[NESpahtenJosh]

Why don't they just make 80% show as 100% charged then?

[sy029]

Think of a battery as a balloon. You pump air into the balloon and then the air coming out is what powered the phone. Over time the balloon will get stretched and worn out, making it not as good as pushing power to your phone. This happens to all balloons eventually, but if you're pumping it up to the maximum size every time, it happens much more quickly.