iPhone Battery — The 40-80% Lie

I’m Rene Ritchie, welcome back to another video where I’m once again busting just the weirdest myths, misconceptions, and straight up misinformation about the iPhone and how it works. This time — Do you need to micro-manage your iPhone charging? Like never let it go below 40% or above 80%? And, spoiler alert, in a word, no. In two words, hell no. No you don’t. Nobody does. Nobody has time for that.

Now, I know, I know… some people will tell you otherwise, even insist otherwise. But that hasn’t been true in ages, like since dinosaur phones roamed the earth ages, and I’m going to explain to you why, and I mean exactly, precisely why. Because that’s how I do.

So, first discharging first. Is…

allowing the battery level to drop down to 10% or less considered a bad practice?


Do these deep discharges exhaust a lithium battery sells faster?

Also nope. Deep discharges exhausting lithium ion batteries just… isn’t a thing.

But if your iPhone shows you 95% battery health, doesn’t that mean 5% of the battery cells have worn out from being charged and discharged over the last year

More nope. First, because there’s only one cell in most phones. Two in a very few. Sometimes because the other components make an L-shape more practical. Sometimes because it’s a foldable and they’re physically separated. Sometimes because the phone maker wants to offer faster charging speeds using two cells in parallel. But you can’t, like, lose 5% of one or two cells.

It’s really just chemistry. Over time, secondary chemical reactions happen that… reduce capacity. There’s build up. There’s gas. You know — science stuff… Bill Nye stuff.

But don’t deep discharges negatively affect the battery. Isn’t that when low power mode comes in at 20% and automatically begin throttling performance and background tasks to prevent the battery from draining even further?

No, no, and… It… doesn’t? At least not for that reason. It tries to prevent the battery from draining not to protect the battery but to protect your ability to keep using your phone for as long as possible. The idea there isn’t to prevent drain below 20% but to give you the absolute most you can get from that 20% until it’s convenient for you to get to a charger. Be that at 19% or 2% or whatever.

So you really don’t have to worry about getting your back on its charger by the time it reaches 30 or 40%?

Not because of the lithium-Ion battery, no. Even Apple’s battery optimization option, which I’ll get to in a thermally hot minute, only talks about managing maximum charge level, not minimum.

But if you personally feel anxiety over having a low battery, or you know you need to go somewhere later and you’ll be using your phone a lot for photos, video, gaming, whatever, and you’ll need a decent charge to do all that, then by all means, charge away. That’s the whole entire point of this video. We humans should never not ever have to worry about when or how much we charge. That’s the iPhones job to manage.

Ok, but what about optimized battery charging for the iPhone where it will wait to charge past 80% until it knows you’re ready to use it based on your charging routine?

Yeah, so, also the whole entire point. The iPhone will manage all this for us and just way, way, way better and beyond what we could ever micro-manage on our own. I mean, back in ye olden days of yore, battery management sucked, and you’d need to reset the system, and do all sorts of jiu-jitsu just to eek out every… energon cube of battery life you could.

But Apple’s been using machine learning and artificial intelligence for years now to do everything from unloading to pre-loading apps into memory, to charging and discharging to prevent it sitting at peak capacity, to more recently offering this Optimized Battery Charging feature where it’ll just idle at 80% until it thinks you’ll want to start using it soon, and then and only then will it push to 100.

Because being at over 80% isn’t bad in and of itself, it’s staying at over 80% for extended periods of time that’s bad. That, and one other major key thing I’ll get to in a literal hot minute.

Which is exactly what the Optimize Battery Charging feature does. So don’t worry or stress or even think about micro-managing 40% or 80% or any of that. Just leave Optimize Battery Charging on and you’re golden.

So it really, really isn’t best to keep your iPhone battery level between 40 and 80%?

Ok. Seriously. Charge your iPhone when you want or need to and take it off the charger when you want or need to and let the charging take care of itself.

What about fast chargers and wireless chargers, don’t they degrade batteries faster?

So… kinda. What really prematurely ages out lithium ion batteries fast is heat. Lithium Ion batteries will die faster in extreme cold, basically because it slows down the chemistry and the power delivery can’t keep up with demand. But when you return to normal operating temperatures, your phone will return to normal operations just fine.

Extreme heat will just break down the chemistry, though, and there’s no returning from that.

And, traditionally, fast chargers and wireless chargers create more heat either all at once or because they’re less efficient, over time. And I say traditionally because companies claim they’re getting better and better at mitigating that heat all the time. But Apple has also prioritized battery health over raw charging speeds for a long time as part of those mitigations.

Honestly, what’s probably most damaging to iPhone batteries these days — all days — is us. We. People. Leaving them out in the sun on hot days, putting them in front of vents or on radiators on cold days. And they’ll gate by cutting brightness, flashing warnings, even shutting down if they get too hot, but they’ll be prematurely aging the whole time that process happens anyway.

So, instead of wasting precious minutes of your life micro-managing your charging, stressing that you start your day with only 80% battery and panicking to plug in before you drop below 40% or, Lords of Kobol forbid, 20%, just don’t leave your iPhone out in the heat or on hot things and you’ll do way, way less damage in the long run and have way, way less stress in the meantime.

And please feel free to share this video with your friends, family, and colleagues, or any of my other explainers like this one on force killing apps. I’ll leave links in the description right below the like button.