Why Your Phone Still Hits 100% With the 80% Limit On
Apple and Google both let phones hit 100% even with the charge limit on. Here is exactly why, how often it happens, and whether it undoes the benefit.
You turned on the 80% charge limit to protect your battery, then woke up to find your phone sitting at 100% anyway. That is not a bug. Both Apple and Google build in periodic full charges on purpose, and they do not hide it, they just do not explain it loudly.
What Apple actually says
Apple's own support page states it plainly: "If you have Charge Limit set to less than 100 percent, your iPhone will occasionally charge to 100 percent to maintain accurate battery state-of-charge estimates." That is the entire disclosure. Apple does not say how often "occasionally" is, what triggers it, or how long the phone stays at 100% before the limit resumes. If your capped iPhone hits 100% every few weeks with no pattern you can predict, that vagueness is why.
What Google actually says, and it is far more specific
Google's Pixel support page does not hide behind a vague word. It states a real number: "To keep its battery capacity readings accurate, your Pixel needs to fully charge at every 10th cycle." This applies even with the Limit to 80% option turned on, and Google adds a second instruction most people never see: leave the phone plugged in for at least 30 minutes after it reaches 100% so the recalibration actually completes. Skip that step often enough and the phone's own read of its battery health can drift from reality.
Does this undo the point of the 80% limit?
No, and the reason is simple arithmetic, not marketing. The 80% limit works by cutting the amount of time a battery cell spends at a high state of charge, since that is what accelerates chemical wear. One full charge out of every ten cycles, or an unquantified "occasional" one on iPhone, is a small fraction of total charging time. The other nine charges still stop at 80%, and that is where nearly all the benefit comes from. A recalibration charge is not the setting failing, it is the setting's own management system checking its work.
Apple vs Google, side by side
| iPhone (Charge Limit) | Pixel (Limit to 80%) | |
|---|---|---|
| Full-charge frequency | "Occasionally," unquantified | Every 10th charge cycle, stated exactly |
| Stated reason | Maintain accurate battery state-of-charge estimates | Keep battery capacity readings accurate |
| What you're told to do | Nothing, it happens automatically | Leave it plugged in 30+ minutes after it hits 100% |
| Where it's documented | support.apple.com/en-us/108055 | support.google.com/pixelphone/answer/6090612 |
What to actually do about it
Nothing. If you see your capped phone at 100% and did not touch the setting, that is the recalibration working as designed, not a reason to distrust the feature or turn it off. The 80% limit is still worth using if your phone spends hours plugged in at a time. If a full charge to 100% shows up right before a day you actually need the extra range, that is a coincidence worth enjoying, not evidence the setting turned itself off. It also has nothing to do with how fast you're using up your total cycle count, a recalibration charge counts the same as any other full cycle, it is not an extra hidden cost.
FAQ
Why does my phone charge to 100% even with the 80% limit on?
Both Apple and Google design this in on purpose. Apple's iPhones do it "occasionally" with no fixed schedule stated; Google's Pixels do it on a stated schedule, every 10th charge cycle, specifically to keep the phone's battery health readings accurate.
Does the periodic full charge damage the battery or cancel the benefit of the limit?
No. It is a small fraction of total charging cycles. The limit's benefit comes from the other charges stopping at 80% instead of 100%, and that benefit holds regardless of one recalibration charge in ten.
Do I need to do anything when my phone hits 100% unexpectedly?
On Pixel, leave it plugged in for at least 30 minutes after it reaches 100% so the recalibration completes properly. On iPhone, Apple gives no extra instruction, the process is automatic.
Is Samsung the same as Pixel or iPhone here?
Samsung's own documentation on this specific recalibration behavior is not public in the same way Apple's and Google's are, so it should not be assumed to match either one without a direct Samsung source. Samsung does publish cycle count and health percentage through its own Battery information screen, just not the recalibration mechanic itself.
A phone's charge habits only matter for the battery already inside it. If you are charging on a rented powerbank instead, on the go, at an event or a station, none of this applies the same way since the battery doing the work isn't yours to manage long-term.
