The results are in from a three-year real-world test of the iPhone’s 80% charging limit, which Apple fully introduced in iOS 18. The numbers clearly show that it works. But the tester who conducted the experiment was still left with a fundamental question: “Is it worth giving up 20% of your battery?”
Key takeaways
After charging to just 80% for a year, the iPhone 17 Pro Max had 97% maximum battery capacity after 277 charge cycles.
An older model used the same way dropped to 93% in its second year and 88% in its third.
The tester reported that “the practical benefit is small,” and a 2024 data analysis likewise concluded that the difference was “statistically significant, but not large.”
Results of a three-year iPhone charging-limit experiment
**Juli Clover**, managing editor at Apple-focused publication MacRumors, shared the figures on Tuesday after testing three generations of Pro Max models in everyday use since 2023, with the 80% charge limit option enabled throughout.
The newest device, the iPhone 17 Pro Max, was set to charge only to 80% throughout the past 12 months. As a result, its battery maximum capacity stood at 97% after a total of 277 charge cycles. It also had fewer charging cycles than the previous model, which recorded 299 in its first year. Clover called it “the best result so far.”
Two older devices used for testing show the longer-term trend. The iPhone 16 Pro Max, kept at the same 80% limit, recorded a maximum battery capacity of 93% after 24 months of use and 343 cycles, down one percentage point from a year earlier. The iPhone 15 Pro Max, after 36 months and 369 cycles, remained at around 88%.
Both devices had recorded 94% after one year of use. Clover said that “the 17 Pro Max’s larger battery and faster charging definitely made it easier to stick to the 80% limit,” but added that she still had to carry a power bank on most outings. She tried to use wired USB-C charging more often than wireless charging, but thought the model’s newly introduced vapor chamber cooling system may have had a greater impact on battery management.
Related article: North Korea’s Lazarus moved $1 billion through Chinese laundering network, JackXBT claims
Juli Clover’s conclusion
The numbers look like “a decent report card,” but the person who ran the test had mixed feelings about the results.
Clover repeatedly questioned whether it was “really a sensible choice to give up one-fifth of the battery you can use every day” just to preserve a few percentage points of maximum capacity. She estimated that a device charged to 100% without an 80% limit would “ultimately show a similar level of battery health.” This year’s test did not include an “unlimited” device for direct comparison.
Clover named **Optimized Battery Charging** as the feature that requires the least user intervention, and said that the 90% and 95% charge-limit options available to users could be practical alternatives. She has already enabled the charge limit on her latest iPhone 18 Pro Max and plans to check its battery condition again in September 2027.
Battery health: what the data shows
External analyses reach the same conclusion: “There is an effect, but it isn’t large.” A German Apple-focused publication analyzed battery-health data from 102 iPhone 15 users in 2024 and found a statistically significant, but not substantial in absolute terms, difference between the group that charged only to 80% and the group that charged to 100%.
Clover’s previous experiments have sometimes pointed in different directions. In a 2024 test, the iPhone 15 Pro Max with an 80% charge limit recorded a maximum battery capacity of 94%, outperforming the devices of two colleagues who had no limit (87% and 90%, respectively). But in 2025, a colleague’s “unlimited” iPhone 16 Pro Max showed battery health two percentage points higher than her limited device.
Apple has stated in its official support documentation that the iPhone 15 series batteries are “designed to retain 80% of their original capacity after 1,000 complete charge cycles under ideal conditions.” That is double the 500-cycle target for previous generations.
Next article: AMD says chip supply will expand significantly in 2027 amid surging AI demand