Four Documents, One Number
One reader reports an iPhone 15 at 81 percent Maximum Capacity after fourteen months and 430 charge cycles, and says the store called it healthy. Another reports 79 percent on an older iPhone at roughly 1,100 cycles, and was quoted a fee. The readings sit two points apart, and both people left thinking the cutoff was invented on the spot.
It was not invented. The figure 80 percent appears in at least four documents bearing on that one line in Settings, and each fastens it to something different. Apple attaches it to a count of charge cycles as a design target. AppleCare+ attaches it to a claim you can file. The European Union attaches it to a bench test a model must pass before sale. Google attaches it to a status word on phones whose own software steers the battery toward it. Your screen does not say which of the four you are reading, and coverage depends entirely on that.
What Apple's 80 Percent Is Attached To
Apple states the design target in one sentence, and the sentence is about cycles, not months. In Apple Support, iPhone battery and performance, the wording is that "Batteries of iPhone 14 models and earlier are designed to retain 80 percent of their original capacity at 500 complete charge cycles under ideal conditions," and that iPhone 15 models are designed to retain that capacity "at 1000 complete charge cycles under ideal conditions." The same page defines the unit: "You complete one charge cycle when you've used an amount that represents 100 percent of your battery's capacity."
The target is a pairing, not a threshold. A phone reading 81 percent at 430 cycles is nowhere near the end of its rating; a phone reading 79 percent at 1,100 cycles has outrun a 500-cycle rating by a wide margin. The identical two-point gap means opposite things once the cycle count sits beside it.
The clause "under ideal conditions" does the same job as the ceiling printed on a charger, the logic we followed in why a 45-watt label is a ceiling rather than a promise. Heat, sustained high charge, and fast charging push a real battery under that curve, and none of that makes the phone faulty.
The Cycle Counter Does Not Stand Still
Further down the same page is a sentence that changes how the two numbers relate: "A complete charge cycle is normalized between 80 percent and 100 percent of original capacity to account for expected diminishing battery capacity over time." The counter is not naively adding up charge against the capacity the cell had on day one. It normalizes across a band, and the band named is 80 to 100 percent of original capacity, exactly the band the design target covers.
So Maximum Capacity and cycle count are not independent measurements you can cross-check. They are two outputs of one estimator that already assumes the battery is losing capacity on schedule. Apple describes the capacity figure in equally modest terms: it "measures the device battery capacity relative to when it was new." Nothing there claims instrument precision, and Apple has shipped an update whose whole purpose was to fix that estimate on specific models.
Which Document Owes You a Battery
On Apple Support, Apple Service and Repair for iPhone Battery, the AppleCare+ term is blunt: "We'll replace the battery for no extra charge if the capacity drops below 80%." On the same page, the Apple Limited Warranty covers the device "against manufacturing issues for one year from the date you bought them," and then the exclusion lands: it "doesn't cover accidental damage or batteries that wear down from normal use."
The 80 percent figure that triggers a free battery lives in the paid plan, and the free one-year warranty carves out the exact thing that brought you under 80 percent. That is not slippery wording but the shape US warranty law gives these two products, and the distinction is written down where nobody looks: eCFR, 16 CFR 700.11, the Federal Trade Commission's interpretation separating a written warranty from a service contract under the Magnuson-Moss Warranty Act.
Paragraph (b) says a written warranty "must be conveyed at the time of sale of the consumer product and the consumer must not give any consideration beyond the purchase price of the consumer product in order to benefit from the agreement." Paragraph (c) then supplies the counter-example in almost the exact shape of an extended plan: "an agreement which calls for some consideration in addition to the purchase price of the consumer product, or which is entered into at some date after the purchase of the consumer product to which it applies, is a service contract." A plan you pay extra for, or add later, is a service contract, and it owes you exactly what it says. That is why the below-80-percent promise reads as generous rather than as an admission of defect.
Under 80 percent with the plan in hand, cite the plan's wording plus the capacity figure. Without the plan, at fourteen months, no clock has run out in your favor, because the warranty never had a wear clock. Which document owns the clock is the whole question, as it was when we traced the ten-business-day count in a billing notice back to the rule that creates it.
Brussels Measures the Same 80 Percent on a Bench
Europe took the number and made it a condition of sale. EUR-Lex, Commission Regulation (EU) 2023/1670 sets ecodesign requirements for smartphones and slate tablets, applying from 20 June 2025. Its Annex II requires that devices "achieve at least 500 cycles at 80 % remaining capacity, to be tested under charging conditions where the charging rate is limited by the battery management system and not by the power delivery capabilities of the power supply."
That trailing clause is the only test condition the requirement itself states: the charging rate is the one the phone's own battery management system allows, not the one the power supply could push. The detailed measurement method sits in an annex not quoted here. The duty falls on the manufacturer, importer or authorised representative for a device model placed on the market, so clearing it is not a reading taken from the unit in your pocket.
The same annex carries the pairing that makes the picture click. Its spare-part rules oblige a maker to make the battery available to professional repairers and end-users alike, and a maker "may provide the battery or batteries ... only to professional repairers" instead only if three conditions hold: "after 500 full charge cycles the battery has, in a fully charged state, a remaining capacity of at least 83 % of the rated capacity"; "the battery endurance in cycles achieves a minimum of 1 000 full charge cycles and after 1 000 full charge cycles the battery has, in a fully charged state, a remaining capacity of at least 80 % of the rated capacity"; and "the device meets IP67 rating." The same 1,000-cycles-to-80-percent shape Apple and recent Pixels publish as a design target is, in European law, the price of keeping the battery behind a repair channel, with an 83 percent checkpoint at 500 cycles no phone screen reports.
One distinction separates the legal number from the visible one: Europe measures against "rated capacity," which the regulation's Article 2 defines as "the amount of electricity declared by the manufacturer that a battery can deliver during a 5-hour period when measured under specified conditions," while Apple measures "relative to when it was new." Two phones can show the same percentage while standing in different places against the rated figure.
The regulation also requires "an optional charging feature selectable by the user which terminates the charging process automatically, when the battery is charged to 80 % of its full capacity," adding that with it on, the maker "may enable the device to periodically fully charge the battery for the purposes of maintaining accurate battery state of charge estimates." So 80 percent also appears as a charge ceiling, and the legal text concedes that the state-of-charge estimate drifts unless the battery occasionally goes to full.
Pixel Steers the Battery Toward the Number
Google publishes ratings in the same form, then does something to the battery Apple does not describe doing. Google Pixel Phone Help, Understand your Pixel battery states that Pixel 3 through Pixel 8 Pro and Pixel Fold "should retain up to 80% capacity for about 800 charge cycles," while Pixel 8a and later "should retain up to 80% capacity for about 1000 charge cycles." Battery health is "an estimate of your device's remaining battery capacity compared to its original capacity," reported as Normal, Reduced, or Unavailable, where Reduced means capacity below 80 percent and Google recommends replacement.
Then the part that reframes the readout. Battery health assistance "adjusts the battery's maximum voltage in stages" starting at 200 cycles and continuing through 1000 cycles, and it also "tunes the phone's charging speed" based on the adjusted capacity. It is available on Pixel 6a and later, though "not available on Pixel Tablet," user-toggleable through the Pixel 9 family, and on by default and not disableable on Pixel 9a and later.
Stage the maximum charge voltage down and the battery accepts less charge by design, from 200 cycles onward. Some of a Pixel's decline is therefore a deliberate software decision aimed at keeping the cell inside its rating, not evidence of early failure. Google does not publish the per-stage voltages, so the contributions cannot be separated from outside. A Pixel percentage is a composite, and only the Reduced label carries a documented recommendation.
Note the availability line that trips up support threads: "Pixel 6a, Pixel 7, Pixel 7 Pro, Pixel 7a, Pixel 8, and Pixel 8 Pro don't indicate battery health status." A phone can run the voltage staging while showing no status at all, the same split between firmware and interface we found in a bulletin carrying two patch levels while the phone shows one.
When the Readout Is the Broken Part
A documented case exists of the percentage itself being wrong, which is the strongest argument against treating it as a measurement. Apple Support, About recalibration of battery health reporting in iOS 14.5 or later describes an update in which "the battery health reporting system will recalibrate maximum battery capacity and peak performance capability" on iPhone 11, iPhone 11 Pro, and iPhone 11 Pro Max. The stated cause is "inaccurate estimates of battery health reporting for some users," with symptoms including "unexpected battery drain behavior or, in a small number of instances, reduced peak performance capability."
Recalibration runs "during regular charge cycles" and "might take a few weeks," and during that window the phone can show "Unable to recommend service at this time." If it succeeds, the number you were worrying about changes with nothing physical having happened to the cell. If the third message appears, "Recalibration of the battery health reporting system was not successful," then "an Apple Authorized Service Provider can replace the battery free of charge to restore full performance and capacity," and Apple adds that the message "does not indicate a safety issue." That is a free battery keyed to a failed estimate rather than to any percentage.
Two other messages matter before arguing about capacity. "Your battery's health is significantly degraded. An Apple Authorized Service Provider can replace the battery to restore full performance and capacity" is the degradation notice. "Unable to verify this iPhone has a genuine Apple battery. Details from this battery may not be accurate" is a different animal, listed for iPhone XS, iPhone XS Max, iPhone XR, and later: the reported figures are not trustworthy. After a third-party repair, that percentage is not evidence of anything.
When This Doesn't Apply
A swollen or deformed battery is not a percentage question. Stop charging and take the device in, whatever the readout says. None of the reasoning above is built for a safety condition.
Performance management is a separate mechanism from capacity. Apple describes iOS dynamically managing performance peaks "to prevent the device from unexpectedly shutting down," and both performance-management messages refer to a battery that could not deliver peak power. A phone can be throttled at a high capacity percentage and untouched at a low one.
The European requirements attach to products placed on the European Union market and apply from 20 June 2025. They are not an entitlement a US buyer can invoke at a counter, and set no threshold your individual phone is measured against. National consumer law can give European buyers remedies unrelated to these cycle figures.
Model coverage is narrower than the discussion suggests: the recalibration behavior was specific to the iPhone 11 family. Pixel battery health status is documented for Pixel 8a and later, not for Pixel Tablet, and the earlier Pixels listed above report none. Refurbished and carrier-branded units can carry a different service contract. Finally, this answers whether a number obliges anyone to replace a battery, not whether you should: a phone at 82 percent that cannot last a workday is a real problem even when no document owes you anything.
Reading Your Own Two Numbers
Write down both figures first, because one alone settles nothing. Put the capacity percentage and the cycle count together against your model's published pairing: 500 cycles for iPhone 14 and earlier, 1,000 for iPhone 15 models, about 800 for Pixel 3 through Pixel 8 Pro and Pixel Fold, about 1,000 for Pixel 8a and later. Ahead of the pairing, you have a battery losing capacity faster than its rating and a conversation worth having. Behind it, the battery is doing what the specification said, and the only open question is who pays.
Then identify which document you are standing on. A paid plan with a below-80-percent term is a contract claim, and the words to quote are the plan's own. A one-year warranty is a defect claim, with wear carved out in writing. A failed recalibration message on an iPhone 11 is its own route to a free battery regardless of percentage. A genuine-battery warning means the figure is disclaimed, so the argument moves to symptoms: shutdowns, hours of use, charging behavior.
The store's answer sounded arbitrary in both cases at the top because 80 percent is doing four jobs at once: the end point of a cycle rating, the entry point of a purchased claim, a bench figure in European law, and a target recent Pixels are managed toward. None of the four is the sentence "your battery is broken." Once you know which one you hold, the number stops being a verdict and goes back to being an estimate with a cycle count standing next to it.
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