A new analysis of Apple iPhone data shows that iPhones perform worse with newer iOS updates if users do not replace the battery. Although the reason for this is not clear, the head researcher behind the analysis believes it may be a behavior employed by Apple to preserve aging batteries.

The new data is part of the Geekbench program run by Primate Labs, a company that develops performance analysis software for both desktops and mobile platforms. For the project, Primate Labs ran tests on thousands of iPhones, plotting how the iPhone 6S and iPhone 7 ran on different versions of iOS, The Guardian reported.  

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Results showed that the iPhone 6S running on iOS 10.2 performed fine, but when the same phones were upgraded to the iOS 10.2.1 in January 2017, they began to gradually perform worse. The same downward performance trend was seen on iPhone 6S running iOS 11.2, an update released in December 2017.

Similar results were also seen on the iPhone 7, with the smartphone’s performances remaining the same for this phone model under iOS 10.2.0, iOS 10.2.1, and iOS 11.1.2, but performance decreasing after an upgrade to iOS 11.2.0, the report showed.

A smartphone's performance does decrease as the phone ages. BEN STANSALL/AFP/Getty Images

Smart phones' lithium batteries are designed to last up to 500 charges, and can last between three and five years, TechAdvisor reported. Once batteries begin to age, users find themselves in a vicious cycle as aging batteries need to be charged more often, but charging batteries more often also causes them to age faster. Aging batteries may also not be able to support more complex processors because they produce less of a current.

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Of course, iPhones are not the only smartphones to decrease in performance as they age. According to Lifehacker, this is just a fact of smartphones; operating system updates can be hard on older hardware. New versions of apps may run slower on older hardware. This problem affects all smartphones, regardless of whether you send green texts or blue.

However, John Poole, Primate Lab founder who wrote the recent report on iPhone battery use and is not affiliated with Apple, suggests that the decrease in performance is not only due to worse battery performance.

“The difference between 10.2.0 and 10.2.1 is too abrupt to be just a function of battery condition. I believe (as do others) that Apple introduced a change to limit performance when battery condition decreases past a certain point,” wrote Poole in the report. Apple did not yet return a request for comment on the Primate Lab findings.

According to Poole, the data seem to suggest that iPhones processor performance reduces with new upgrades to mask failing battery. This suggestion may also support the many anecdotal observations that iPhone performance decreases with new Apple updates.