MacBook's 80% Battery Charge Limit not working as expected

What you’re seeing is actually expected behavior — not a bug.

On macOS 26  Tahoe, the battery charge limit (80%) only actively works when the system is powered on and macOS can manage charging. 

When your MacBook is shut down completely, the operating system isn’t running.

So , the charging is handled at a lower firmware level that does not enforce the 80% limit strict

https://discussions.apple.com/thread/256270027?answerId=261887138022&sortBy=oldest_first#261887138022

Even with the Charging Limit configured to 80%, the laptop will occasionally charge the battery 100% in order to maintain battery health & behavior (so it keeps it calibrated for when the battery gets near 0% so it can hibernate instead of powering off).

The Optimized Charging and the Charging Limit feature only work while the laptop is booted into macOS. When the laptop is powered off these options will be ignored.

Apple says the battery charge may vary by up to 5% above & below.

See the following Apple article regarding how Charging Limit feature works:

About Optimized Battery Charging and Charge Limit on Mac - Apple Support

pippadeflauf wrote:

On April 16 the battery dropped to 7%, and continued charging to 100%.

Today, April 24, my laptop went from about 48% battery to 100%, and right now the Settings pane still says "Charging: 100%" "Charging to 80% limit"

I'm filing a bug report but wanted to add to the discussion here for those who are experiencing this as well.

Apple provides fairly minimal documentation about its battery health management, which seems adequate for most but maybe not all users.

First, iPhone battery management is different from battery management for Macs. Same for Apple watches. Because watches and phones are designed for most of their use to be off the charger.

Second, one needs to read that minimal documentation carefully but Apple does say that it may charge devices to 100% based on use patterns. I have spoken to Apple Store "Genius Bar" people about this, so can't prove it to you in writing, but they told me that if someone repeatedly uses a Mac laptop in a way that takes its charge to very low levels, the battery management will charge to 100% more frequently because it has "learned" that this user needs as full a charge as possible. You took yours to 7%. For such a user, charging only to 80% might not be adequate and charging to 100% might make more sense.

I see this on my phone and watch sometimes, after several days of running the battery down to 20% or 10% it decides to charge past 80% to 100% for a few days. I haven't seen it on my laptop as much because my laptop is connected to the charger most of the time, so the laptop seems to stay at 80% almost all the time. But sometimes it will stay at a different value, like 72%. Earlier this week I accidentally allowed it to go down to almost 0% and for several days now it has been charging to 100%, but now has returned to the 80% value.

If you repeatedly use your laptop off the charger and it goes down to 7%, I expect, based on what the Apple employee told me, that this will be detected by the battery management system and charging more often to 100% may result.

On the other hand, if your laptop drops to 7% while connected to the charger, then either the charger is defective, or the battery is defective, or something else is wrong. But that sounds more like hardware anomaly, not a Mac OS bug.

I doubt there is a MacOS bug at play here as I have used multiple MacBook Pros ranging from 2019 to 2024 models and they all seem to basically behave the same with the battery health management. The 2019 model is an Intel one and it does not present the user with an option to specify the charge limit but otherwise it behaves much like the others. If there were a bug in the MacOS, I expect there would be widespread reports of problems.

I think you may be over focusing on the battery and if you enjoy that, do continue, but all batteries basically get used up eventually and the way Apple manages the charge levels should extend the life of the battery significantly. There are papers published on lithium battery lifetimes and while the "optimal" steady state charge level might be closer to 60%-70% than 80%, I think 80% represents a compromise between longer battery lifetime versus usability (going out with a laptop at 60% is not very practical if it will be off the charger for a long time). And I think looking for the charge level to always just lock at precisely 80% is ignoring the other facets that Apple's battery health management takes into account.

Feel free to report a bug but Apple engineering knows how the batteries are managed and won't consider what you describe above as a bug.

Abdelrhman_Atef wrote:

Thanks for the detailed breakdown!

That’s a really interesting point about the 7% drop—I didn't think the system would 'learn' from that and try to compensate by charging more. Makes sense now why it’s ignoring the limit.

I can't prove that's what happened but Apple's own documentation says that their battery management may charge past the user-specified limit if usage patterns indicate that this is called for, or for calibration purposes.

I guess I was diving too deep into the numbers because I’m a CS student and I like knowing how things work under the hood.

That's reasonable, and I have worked in spacecraft software for several decades and the battery management is of great interest to me too because when we fly spacecraft across the solar system (two have actually left the solar system, Voyager I and Voyager II), the longevity of the spacecraft and the mission is basically dependent on finding ways to sustain the rechargeable batteries longer. And some of those spacecraft batteries can last for 20 years or more, and how to do that is of intense study by some of us in that business. The Mars Reconnaissance Orbiter, presently in orbit around Mars and making science measurements as well as relaying data from the Mars surface rovers back to Earth, was launched in 2005 and is still operating at Mars, with very careful handling of its batteries, which are space qualified special devices. That said, our laptops are different, those are mass produced and their batteries are by design built to last something like 5 to 7 years or 1000 cycles, whichever comes first. Analogous perhaps to automobile tires, which are guaranteed to wear out. Even if just left on the shelf unused, these laptop batteries will wear out over time. The best a user can do is take reasonable steps to sustain the battery, such as utilize Apple's battery health management and not run the battery down or up in charge unnecessarily a lot. I suspect if you made a full time job out of trying to optimize battery usage, you might improve very slightly over Apple's built in system, but maybe not, and if so, not by much.

I do share your interest in the software Apple uses for this, but I think you will find pursuit of this a bit frustrating because Apple provides only minimal documentation ... after all, this is probably something of a trade secret of sorts. So we can speculate together but we will probably really never know for sure.

Here are some resources you may find interesting:

https://www.rdbatteries.com/blog/post/how-to-charge-lithium-batteries.html?srsltid=AfmBOoovvha5e3fusDq_bsK1JEgiOlX0E5AWUgpsoBdDnBm_6Zcz1gd3 "The optimal charge range for most lithium battery applications falls between 20% and 80% state of charge ... maintaining charge levels within this range significantly reduces the stress placed on the battery's electrode materials and electrolyte, resulting in slower degradation rates and extended cycle life ... Most lithium batteries should not be discharged below 10-15% state of charge, as deeper discharges can cause irreversible capacity loss and potentially damage the battery's internal structure."

https://www.litime.com/blogs/tips-and-tricks/the-20-80-rule-for-batteries?srsltid=AfmBOopeyWTuTTJJSh5qOsjzmyDqacHMbgGScbMMMLAg-nQdFAJX1qCU "The 20-80 rule means keeping your battery’s state of charge (SOC) between 20% and 80% instead of fully charging to 100% or draining to 0%. By avoiding extreme voltages, you reduce chemical stress inside the cells and significantly extend battery life."

https://www.large-battery.com/blog/tolerance-to-full-charge-lithium-battery/ "Don’t charge lithium batteries to 100% all the time. Keeping the charge between 20% and 80% makes them last longer. Use a Battery Management System (BMS) to check charge levels. It stops overcharging and spreads power evenly in the battery."

There are also scores of scholarly refereed journal papers on this topic. You can search for them online, many are available for free.

Abdelrhman_Atef wrote:

Battery Charge Limit (80%) not working on MacBook

Hi,

I’m using the 80% Charge Limit feature on my MacBook, and I have "Optimized Battery Charging" turned off.

(macOS Tahoe)

turn on Optimized Battery Charging

You do not have to micro-manage battery charging, let the built in software work for you.

The rule of thumb—if you are near the mains leave it plugged in, if you need the portability then run on the battery only—this is how you help optimize your battery charging and extend the working life of your battery by reducing the cycle count.

I've been experiencing issues with this as well. I have a couple of replies for this thread and my own account of what appears to be a bug.

What you’re seeing is actually expected behavior — not a bug.

On macOS 26  Tahoe, the battery charge limit (80%) only actively works when the system is powered on and macOS can manage charging. 

When your MacBook is shut down completely, the operating system isn’t running.

So , the charging is handled at a lower firmware level that does not enforce the 80% limit strict

https://discussions.apple.com/thread/256270027?answerId=261887138022&sortBy=oldest_first#261887138022

At what point did the post state that their MacBook was shut down? They do state, "The problem is that the system often ignores the limit." I doubt they are really going to actively shut it down, especially frequently, as the sleep states of Apple silicon are excellent. I did see that in the thread you linked to here, that poster did say their Mac was "shutdown" -- am I missing something?

Also, can I please get some sort of reference for your statement about expected behavior? Your link is in reference to your own comment... I am not disagreeing, but I would be interested in specifics. I haven't been able to find pertinent information in developer documentation either (or NDA documentation which I will not discuss here).

My own experience with this issue:

I have also been having issues with my MBA (A3240, Tahoe 26.4) ignoring the charging limit, regardless of system power state (fully on or asleep). I have also had it continue charging and holding charge while displaying that it is limiting the charge to 80% (whereas per the Charge Limit section in this support article it should wait for a 5% drop).

It functioned as expected a few times but now I have noticed it not working pretty consistently.

I just verified some examples from my screenshots which I can attach if requested (I'd need to blur out some tax info first).

On April 16 the battery dropped to 7%, and continued charging to 100%. I was using the laptop the entire time. I did some research and read some other discussions of this and the support article. Meanwhile it continued to tick up until it hit 100%. The menu bar battery tab and the battery panel in Settings both said "Charging to 80% limit." The panel in Settings said "Charging: 99%" simultaneously.

I chalked this up to doing a full cycle to keep calibration especially after going under 10%.

But I have had it happen again and again.

I have seen it stated elsewhere in this forum that the charge limit doesn't occur when the laptop goes into sleep mode, but I take issue with this. First off, this is not stated anywhere in Apple support documents or official product pages (e.g. the footnotes for 26.4's release promotion). Second, I observed it functioning while asleep multiple times, as I am a nerd and found interest in it (and took note that the charge indicator remained orange despite it being a software-controlled indicator). Third, that just does not make sense. The feature would have parity with other devices -- my iPhone 17, for example, hits and holds at 90% no matter what.

Today, April 24, my laptop went from about 48% battery to 100%, and right now the Settings pane still says "Charging: 100%" "Charging to 80% limit"

I'm filing a bug report but wanted to add to the discussion here for those who are experiencing this as well.

So there is no problem until you expose it. For me, I have no issues when my MacBook is turned on. Its charges to 85% all of the time and never not. I never let my battery get below 50% either. So my entire range on both my phones, devices and laptops (anything with a battery is 50%-85%). Perfection !

Here is the issue. Power down your MacBook when it is somewhere below 85%... now plug in the charger. It will now ignore the battery charging limit and charge your battery to 100% (therefore shortening its life). So that's why I came here and found this thread. Apparently different people here are concerned about slightly different issues. But mine is universal simple. Battery charging limit should be a limit no matter what. So apparently they got its function in the wrong place of the firmware and it can't do it when powered down. Which is a huge oversight IMO.

(among many other things off subject I could point out but won't.. don't even get me started on the address book - lol)

Roulette Records wrote:

Here is the issue. Power down your MacBook when it is somewhere below 85%... now plug in the charger. It will now ignore the battery charging limit and charge your battery to 100% (therefore shortening its life). So that's why I came here and found this thread. Apparently different people here are concerned about slightly different issues. But mine is universal simple. Battery charging limit should be a limit no matter what. So apparently they got its function in the wrong place of the firmware and it can't do it when powered down. Which is a huge oversight IMO.

You can provide Apple with product feedback here:

Product Feedback - Apple

I've set mine to 80% and out of the like 4 times i have charged my mac since i've put this limit in place it has charged to 100% 3 times.... So this doesn't seem to be just an occasional thing. I suspect it's a bug. Edit: the macbook is turned on or sleeping while charging so it being turned off is not my issue

The problem is Apple has implemented the Optimized Charging and Charging Limits differently than most third party apps implement such features. And people see "Charging Limit" and think it will remain at that charge level permanently which is not the case. And like Optimized Charging, the Charging Limit feature may take time to learn how you use the laptop & battery before settling into a more regular charging limit.

People worry way too much about their batteries. It is best to for the user to just ignore the battery & just let macOS handle the battery especially with Optimized Charging. Only start reviewing the battery health & condition when the battery no longer provides the runtime you expect, otherwise ignore the battery & just use the laptop.

And @steve626 has written a nice explanation as well. Plus Apple is very secretive & tends to write very poor & confusing documentation. It is unfortunate that Apple isn't a bit more forthcoming on details.

Roulette Records wrote:

Here is the issue. Power down your MacBook when it is somewhere below 85%... now plug in the charger. It will now ignore the battery charging limit and charge your battery to 100% (therefore shortening its life). ... So apparently they got its function in the wrong place of the firmware and it can't do it when powered down. Which is a huge oversight IMO.

Not necessarily.

Simply charging to 100% now and then is not really a problem. Keeping it at 100% for very extended periods may shorten the battery life. I think you are over thinking this.

And if Apple complexified the firmware so it is managing battery level even when shut down, that will use more energy and run the battery down faster when turned off and not connected to power. Which would generate more complaints in Apple Discussions ...

Follow on from yet another 80% charging level not being respected

https://discussions.apple.com/thread/256285693?sortBy=oldest_first

Turn off battery optimization and it will no longer do that.

Its AI just calculating what it thinks is best to do.

The closest I can get.

Optimized Battery Charging is designed to reduce the wear on your battery and improve its lifespan by reducing the time that your Mac spends fully charged.

It uses on-device machine learning to learn your daily charging routine so that it can delay charging past 80% in certain situations, such as when it predicts that your Mac will be connected to power for an extended period of time. Optimized Battery Charging aims to ensure that your Mac is fully charged by the time it expects you to need a full charge. To limit what your Mac considers a full charge, you can also set a Charge Limit.

Using the " on-device machine learning " which by its' nature, is Built Into the Operating System.

It would seem reasonable to believe

Unless the computer is in the ON Position and the Operating System is in fact loaded

The " on-device machine learning " process would not function

Thusly, we arrive at the conclusion previously mentioned

To further Test this conclusion

I have Tested this on 1 M5 Laptop, 1 M4 Laptop and 1 M2 Laptop, each running Tahoe 26.4.1