In-Depth iPhone Battery Experiment Pits Slow Charging Against Fast Charging

[Reeneman]

„without overthinking“

Regarding charging it would be so so nice if more people would follow this. But tech forums and Reddit probably would loose around 30% of its traffic in that case.

 

[Reeneman]

I sell my phone every 2-4 years and offsetting by charging to 80% make the device more financially lucrative for trade-in/resale value without having to take a financial hit.

Been charging my iPhone 16 Pro to 80% since Day 01 with the few instance to charge to 100% due to battery calibration and 14 months later it’s at 100% with low recharge cycles. Using the device without restrictions.

This test jus proves that charging to 80% is offsetting the remaining capacity; big revelation 😒

This capacity value is also not a scientific and precise measurement by iOS, als also stated in the video. Nevertheless, still being at 100% after one year is based on a lucky pick with your phone. Your battery most likely came with a capacity way above 100% out of the box. That mostly explains why you are still at 100% capacity. Sure a good behaviour with charging could also help but it won’t avoid battery degration.

 

[Velin]

I sell my phone every 2-4 years and offsetting by charging to 80% make the device more financially lucrative for trade-in/resale value without having to take a financial hit.

You are earning nothing by doing this. Absolutely nothing.

Financially lucrative? C’mon man. Ain’t no one paying more for a 2021 iPhone because battery health says “95%” versus “92%.” You are simply wasting time.

As for trade in, Apple pays you literally nothing for increased battery capacity. Apple’s trade-in metric is strictly model, year, no catastrophic defects = predetermined price. Apple lists these criteria and values, go look for yourself. And this is the same for any third-party reseller. Nearly all don’t even ask about remaining battery percentage. No one cares. And no one is paying for a slightly higher percentage. No. One. Is. Paying. Period, end of story.

We knew this “80%” charge limitation basically did nothing. This is the second comprehensive report confirming it. We also knew the purported ludicrous justifications would follow in this thread, just as it has in other threads. The “financial” justifications for 80% are pure fiction. Pure fiction.

Anyone using this toggle = total waste of time. 99.9999% of people don’t care. Including Apple, which you can confirm yourself.

 

[code-m]

This capacity value is also not a scientific and precise measurement by iOS, als also stated in the video. Nevertheless, still being at 100% after one year is based on a lucky pick with your phone. Your battery most likely came with a capacity way above 100% out of the box. That mostly explains why you are still at 100% capacity. Sure a good behaviour with charging could also help but it won’t avoid battery degration.

Never said it won’t degrade but it is extending its shelf life for when it comes time to sell. If around the 2 year mark it’s around 96% that is still above average and at three years if at 92% I will be golden.

 

[code-m]

You are earning nothing by doing this. Absolutely nothing.

Financially lucrative? C’mon man. Ain’t no one paying more for a 2021 iPhone because battery health says “95%” versus “92%.” You are simply wasting time.

As for trade in, Apple pays you literally nothing for increased battery capacity. Apple’s trade-in metric is strictly model, year, no catastrophic defects = predetermined price. Apple lists these criteria and values, go look for yourself. And this is the same for any third-party reseller. Nearly all don’t even ask about remaining battery percentage. No one cares. And no one is paying for a slightly higher percentage. No. One. Is. Paying. Period, end of story.

We knew this “80%” charge limitation basically did nothing. This is the second comprehensive report confirming it. We also knew the purported ludicrous justifications would follow in this thread, just as it has in other threads. The “financial” justifications for 80% are pure fiction. Pure fiction.

Anyone using this toggle = total waste of time. 99.9999% of people don’t care. Including Apple, which you can confirm yourself.

Some vendors do care for battery life and cycles for devices and laptops. The closer it is to 80% you loose out between $5-20. Again it’s peanut money to some but some vendors and customers do care the majority don’t and no I would never trade-in anything to Apple when there are better options out there.

 

[code-m]

This capacity value is also not a scientific and precise measurement by iOS, als also stated in the video. Nevertheless, still being at 100% after one year is based on a lucky pick with your phone. Your battery most likely came with a capacity way above 100% out of the box. That mostly explains why you are still at 100% capacity. Sure a good behaviour with charging could also help but it won’t avoid battery degration.

Maybe I got lucky this time but k recall that my iPhone 12 Pro was around 92-94% after a year.

 

[DougiePhresh]

It has to with the documented behaviors of li-ion batteries. It may not make much of a difference with an $89 iPhone battery, but on a $15,000 ev battery it can make a difference.

Okay, yea - I should have specified. I was talking about phones. I can absolutely appreciate that behavior on an EV.

 

[DougiePhresh]

I sell my phone every 2-4 years and offsetting by charging to 80% make the device more financially lucrative for trade-in/resale value without having to take a financial hit.

Been charging my iPhone 16 Pro to 80% since Day 01 with the few instance to charge to 100% due to battery calibration and 14 months later it’s at 100% with low recharge cycles. Using the device without restrictions.

This test jus proves that charging to 80% is offsetting the remaining capacity; big revelation 😒

There is no way all the effort you go though to make sure you are only charging to 80% is worth the extra 20 bucks you get every four years on resale … unless there is a setting that will automatically stop charging at 80%, you need to stop wasting your time haha

 

[Madonepro]

Now to discover, if this applies to Apple Watch, and whether capacity of battery impacts lifespan.

 

[steve62388]

For sure.

If you limit yourself to 80% then after 4 or 5 years you can avoid a battery that only... has 80% of it's capacity left?

What exactly have you accomplished?

Let's imagine a phone owned for 6 years. One person limits it to 80% and has 80% capacity for 6 years. The other person doesn't limit it at all and ends up with 80% capacity and maybe a smidge under for a year or two?

...I really don't get it. Like genuinely. How is the first scenario not the obviously, clearly, no brainer, no question worse scenario? How is a capacity life of 100, 96, 92, 88, 82, 80 better than a capacity lifetime by year of 80, 80, 80, 80, 80, 80?

Because that's not what the test showed.

It showed that fast charging the phone over 500 cycles (approximately 1.5 years) between 5% and 100% degraded it on average by 12.3% compared to 8.3% when between 30% and 80%.

So your numbers should look something like 100, 91.6, 83.9, 76.8, 70.2, 64.2 and 100, 94.4, 89.0, 83.9, 79.1, 74.6.

Apple will be recommending you replace your battery about half way through year three of the first phone but not until the end of year four of the second. So it does come into play if you keep your phone for a long time.

Caveat: I have no idea exactly how the health will degrade over that length of time, but without testing neither does anyone else. I have just assumed the same rate (which is better than a total guess).

I keep my phones pretty much until they either die or become unusable because the battery is cooked, and before then I'll even resort to carrying a small power bank with me. If I can eke out another year from my phone then that lets me postpone a big purchase or get the newer model a year later. I don't 'sail' my battery on my iPhone, I don't have the 80% charge limit on it anyway because it's a 14 Pro. But I do use AlDente on my MacBook, which does the same thing, because I'm almost always next to a power socket.

 

[Analog Kid]

Okay, but exactly what does that have to do with preserving battery health? You are welcome to your opinion clearly. So maybe it was just that?

My cycle counts tend to be quite high every year, and I tend to do a ton of batch photo edits, and timeline critical 4K video editing on device for my clients. My clients also pay for fast turnaround, so I keep my devices fresh for the speed bumps that make a difference in my workflow. My use case, not yours.

Not that I need further validation for my business expenses, but I also enjoy new devices and often hand them down to family or sell to friends.

Either way, taking care of a device and battery keeps items from the landfill and reduces the need to manufacture new devices or battery cells.

For work (day job), I deal with 1 - 2 megawat blocks of UPS systems with various types of lithium batteries from Samsung, Toshiba and new Zinc technology from others. I am taking as much suggestions from these entities as I do from phone manufacturers on how to maintain battery health and warranty.

I’ll keep doing what I can to keep my cells in good shape.

And what you're doing has little to no impact on your phone battery life. There's no difference in result between your careful approach and my careless approach. That's my point.

The iPhone isn't a megawatt UPS and it doesn't use zinc batteries-- applying what you're told about those systems to you phone makes as much sense as saying you work at a nuclear power plant so know a thing or two about fire crackers.

 

[SebCohen]

Also…People….a new battery for your iPhone Pro ISNT THAT MUCH MONEY. Just, you know, saying.

 

[bigglow]

Now to discover, if this applies to Apple Watch, and whether capacity of battery impacts lifespan.

When I upgraded from a Series 4 to a 10 I still used the previous USB-A cable until I sold my Series 4 and started using the USB-C cable.

As I plan to use it until 2030 I would prefer to use the USB-A cable.

 

[NativeMac]

I like tests like these. It’s puts the rubber to the road so to speak. It is just like what they found doing the 80% battery test. It is slightly better overall, but such a small real world gain.

 

[Adam-Jobs]

This comes up a lot and every test is more or less the same.

Marginal benefits if you make some pretty significant compromises every day for forever.

If you only charge to 80%, your capacity will hold slightly longer. Capacity that... you're not using.

If you fast charge every day for years all the way to 100%; you'll still have 80% capacity at the end of several years. Capacity that you would've been artificially limiting yourself to the entire time.

Feels very "cover the couch in plastic" to me. Sure I guess it improves it somewhat; but is it worth not getting to actually use the "thing"?

And ultimately, battery replacements from Apple are both reasonably priced and available for a very long time, with third party options virtually indefinitely.

I keep my phones for a really long time so, in theory, I'm the one this information most benefits. The only thing I actually do is make sure to use a slow charger on my nightstand. When I plug it in at night, it's going to be plugged in for the next several hours so there's no benefit to fast charging. Beyond that, it gets hit with a fast charger if I ever need to charge in the middle of the day. Always to 100%. And after 3-4 years the battery capacity starts to get noticeably poorer. A hundred bucks (give or take) at the Apple Store (free with AppleCare+) and I walk away with a brand new battery. And most people will have replaced their phone long before then.

What would you consider a slow charger?

 

[coolfactor]

It just doesn’t make sense to limit yourself to stay within a range now to possibly save a few percentage points later.

Battery charge in involves electrical "pressure". Try filling a tank with high-pressure liquid to 100% 500 times a year and see how long the gaskets hold versus going to just 80%. That extra 20% will add a lot of extra stress causing things to wear out sooner.

 

[HazeAndHahmahneez]

You are earning nothing by doing this. Absolutely nothing.

Financially lucrative? C’mon man. Ain’t no one paying more for a 2021 iPhone because battery health says “95%” versus “92%.” You are simply wasting time.

As for trade in, Apple pays you literally nothing for increased battery capacity. Apple’s trade-in metric is strictly model, year, no catastrophic defects = predetermined price. Apple lists these criteria and values, go look for yourself. And this is the same for any third-party reseller. Nearly all don’t even ask about remaining battery percentage. No one cares. And no one is paying for a slightly higher percentage. No. One. Is. Paying. Period, end of story.

We knew this “80%” charge limitation basically did nothing. This is the second comprehensive report confirming it. We also knew the purported ludicrous justifications would follow in this thread, just as it has in other threads. The “financial” justifications for 80% are pure fiction. Pure fiction.

Anyone using this toggle = total waste of time. 99.9999% of people don’t care. Including Apple, which you can confirm yourself.

I’ll hafta respectfully disagree w you here. I think batt. % def. Matters on the used market..swappa first comes to mind and next eBay..

 

[AlanBeyond]

So, is that kid in Junior High, or...?

Not sure if you're really asking because the initial caps, but he's 25 and we were schoolmates back in high school in Shanxi Province, China. Then he went to Beijing University of Posts and Telecommunications and major in, well, telecommunications, so he's a professional in phones lol

 

[frownface]

My tried and true method would be to absolutely flog the phone to get it below 80% so it gets replaced under warranty (2 years down here)

Once the battery's been replaced; baby it so it lasts the next 5 years 😆

I remember my old iphone5 dropping to 78% by about the 22 month mark. Incidentally i didn't even know because back then ios didn't report battery health. But i brought my phone in for a different reason and while there they did some diagnostics and said my batt was at 78% so replaced it free of charge. Win.

 

[ignatius345]

the best way to charge an iPhone is "however you like," without overthinking it and trading mental energy for a tiny bit of battery life.

Exactly. Same for Macs. Use it as you see fit, charge it when you need to. No need to turn battery management into some kind of weird hobby. It's a consumable part.

 

[ignatius345]

Wish I could limit my macbook to 80% as it's docked 24/7. I don't limit my devices that are mobile for the already discussed reasons.

It should happen automatically AFAIK. My grandmother has a MacBook Air that never gets unplugged, and every time I remote in to help her with something it is charged to 80% with a message in the battery menu that says that it's limited because it's "rarely used on battery".

 

[Poisednoise]

More than minimally, I would say. The 5-100% iPhone lost 12% capacity, while the 30-80% iPhone lost only 8% capacity. This means the 5-100% iPhone lost battery capacity 50% faster.

Yes, but I feel there’s a major flaw in their testing. They did 500 charge-discharges of ALL the phones, rather than calculating how many cycles would have been required to ensure a similar level of chemical change. So, the slow and fast charging test was done 500 times from 5% to 100%. That’s effectively (500 x 0.95=475) complete charge cycles. The ones going from 30-80 only had (500 x 0.5=250) complete charge cycles. On that basis it would appear that had they actually done the correct number of cycles on the 30-80 phone it would have lost (475/250 x 8=15.2%), which is significantly worse.

 

[klasma]

Yes, but I feel there’s a major flaw in their testing. They did 500 charge-discharges of ALL the phones, rather than calculating how many cycles would have been required to ensure a similar level of chemical change. So, the slow and fast charging test was done 500 times from 5% to 100%. That’s effectively (500 x 0.95=475) complete charge cycles. The ones going from 30-80 only had (500 x 0.5=250) complete charge cycles. On that basis it would appear that had they actually done the correct number of cycles on the 30-80 phone it would have lost (475/250 x 8=15.2%), which is significantly worse.

They state that they counted one charge-discharge of the 5-100% group as 0.95 cycles, and one charge-discharge of the 30-80% group as 0.5 cycles. That means that to reach the 500 cycles, they performed 526 charges-discharges for the 5-100% group and 1000 charges-discharges for the 30-80% group. This should also correspond to roughly the same total discharge time.

What would be interesting is if the lower end (5 vs. 30%) or the higher end (80 vs. 100%) matters more. It's certainly not clear that they would contribute equally to the degradation.

 

[840quadra]

And what you're doing has little to no impact on your phone battery life. There's no difference in result between your careful approach and my careless approach. That's my point.

The iPhone isn't a megawatt UPS and it doesn't use zinc batteries-- applying what you're told about those systems to you phone makes as much sense as saying you work at a nuclear power plant so know a thing or two about fire crackers.

Your focus on my mention of zinc batteries, ignoring all else is telling. It is one of the 3 technologies actually. Samsung is lithium ion, Toshiba SCiB batteries use Lithium Titanium Oxide formula, and the last I mention is zinc.

Unfortunately it seems that you do not realize that many of these technologies combine hundreds (and thousands) of small cells into singular banks of batteries, and that they effectively act the same at scale as do smaller portable devices. Scale has many positives and negatives (no pun intended), and lessons learned in all have helped improve the technology.

Sorry but my work experience, training, and review of many articles have shaped the viewpoint on charging and cell stress. We agree to disagree.