Woman spends year charging iPhone 16 Pro Max to only 80% to uncover impact on battery health

A woman spent an entire year only charging her iPhone 16 Pro Max to only 80% in order to uncover the impact it would have on the device’s battery health.

Writing a post on MacRumors, the woman shared how she conducted the experiment in order to test the ‘limits on battery longevity’.

She wrote: “Since September 2024, my ‌iPhone 16‌ Pro Max has been limited to an 80 percent charge, with no cheating. As of today, my battery's maximum capacity is at 94 percent with 299 charge cycles.

“With last year's test, I spent a lot of time with my battery below 20 percent. I saw some comments suggesting that draining it so low could also affect battery capacity over time, so this year, I tried hard to keep my battery between 20 and 80 percent. I wasn't always successful, but my ‌iPhone 16‌ Pro Max was in that middle charge area most of the time.”

The woman is now conducting the experiment with a third iPhone model (Kevin Carter/Getty Images)

The woman went on to say that she believes her battery capacity is ‘about average’, having found that her previous experiment with her iPhone 15 Pro Max also left the device at 94% battery capacity after a year.

She continued: “I did a mix of charging via MagSafe and charging with USB-C, and my ‌iPhone 16‌ Pro Max can get hot when charging over ‌MagSafe‌, especially with ‌MagSafe‌ battery packs. Since I was trying to keep above a 20 percent charge, I did more wireless charging when I was out. I can't help but wonder if heat was an issue this year.

“It continued to be inconvenient limiting my ‌iPhone‌ battery to an 80 percent charge. It was fine when home, but if I was out and wanted to use the camera or needed GPS, it often wasn't enough battery. When you set an 80 percent charge limit, the ‌iPhone‌ will charge to full every so often to calibrate, and I appreciated surprise days with 20 percent extra battery.”

The woman found the results of the iPhone experiment to be 'disappointing' (imageBROKER/Valentin Wolf/Getty Images)

However, the woman said that she didn’t think the outcome ‘was worth’ the effort taken to keep her phone at a maximum of 80% charge, and admitted that she had found the results to be ‘disappointing’.

She added: “I have upgraded to the iPhone 17 Pro Max and did already limit it to an 80 percent charge for another 12-month test. I'm interested to see how the larger battery changes things, and whether the switch to aluminum will make a difference.”