Adrian Kingsley-Hughes/ZDNET
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ZDNET’s key takeaways
- The battery in my 15 Pro Max was awful after 18 months of use.
- I did everything Apple suggested to keep it in tip-top condition.
- I’m going back to 100% charging with the iPhone 17 Pro Max.
When I got my iPhone 15 Pro Max in September 2023, I decided that I’d do everything I could to make the battery last. Well, an accident destroyed that handset, so I restarted the experiment in March 2024.
Also: The best power banks you can buy in 2025
I wanted to see just how much lifespan I could get out of the battery.
Battery life obsession
In my experience, no topic generates more articles, blog posts, and YouTube videos than how to get the best possible battery life from your iPhone, both daily runtime and overall lifespan. It’s also the topic on which I get the most questions and comments.
People have been obsessed with their iPhone’s battery life since day one, and the more metrics and tweaks Apple adds to iOS to delve into what the battery is doing, the worse it has become. Once Apple even added a feature that allowed users to cap battery charge levels to prolong the lifespan of their battery.
Also: Changing these 6 settings on my iPad greatly extended its battery life by hours
But if every minute of runtime, every percentage point of battery life matters, does it make sense to sacrifice 20% — or, to put that another way, one-fifth — of your battery’s capacity?
It seems the temptation of the iPhone lasting longer makes the tradeoff worth it. After all, Apple claims that iPhone 15 models and later can “retain 80% of their original capacity at 1,000 complete charge cycles under ideal conditions.” I was curious as to what “under ideal conditions” meant, but I was determined to give my battery the best chance possible.
Also: Changing these settings greatly improved my iPhone’s battery life
So I set my battery charge limit to 80%, putting a significant but manageable dent in my daily runtime (manageable initially, at least), and got on with my life.
Initially, things were good
Great, in fact. After the first few days of battery-induced anxiety, I no longer thought about or noticed the reduced battery level, and I would rarely end the day with less than 35% charge.
A little over a year and 355 recharge cycles — about one a day — into the experiment, the battery’s maximum capacity had dropped to 91%.
By this point, I was already starting to feel the pinch from the combination of only charging to 80% and the battery wear. Those days when my iPhone would charge all the way to 100% for calibration purposes — it does this occasionally despite the limit — were like a breath of fresh air.
Also: I changed these 8 Apple Watch settings to significantly extend battery life
Battery anxiety returned.
I am a heavy iPhone user, and it’s never more than an arm’s reach away. And I know that heavy usage not only accelerates battery degradation because of the increased recharge cycles, but also intensifies it, reducing the overall lifespan of the battery cells.
I persisted
Fast forward to the beginning of September.
The iPhone was 17 months old, and the battery had 501 recharge cycles under its belt, almost exactly halfway through those 1,000 recharge cycles, with maximum capacity at 89%. Battery life was horrendous. I’d start the day at 80% charge, and by mid to late afternoon, it was hovering close to — if not dipped below — the 20% zone. By this point, power banks had become an essential part of my everyday carry.
Also: I tested the iPhone 17 Pro Max, and this feature alone justifies an upgrade from the 16
I even temporarily raised the charge limit to 100%, and while that helped, battery life was still horrible.
And at this level, I couldn’t even pay Apple to replace the battery, because outside of exceptional circumstances, you have to wait for the maximum capacity to drop below 80%.
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So, for me at least, the effective lifespan of a top-of-the-line iPhone Pro Max is less than two years.
So I gave up and bought an iPhone 17 Pro Max, and once again I can make it through a day without needing a charge. It’s a night-and-day difference.
The iPhone 17 Pro Max is good for a long day… for now.
Adrian Kingsley-Hughes/ZDNET
A sample of one
Maybe my battery was particularly puny, or maybe it’s me. But I’m not the only one to feel that sacrificing 20% of my battery capacity in exchange for the promise of better battery life isn’t worth it. And I’m not the only one.
Also: iPhone battery worse after updating to iOS 26? Here’s why, and how I fixed it
Juli Clover, writing for MacRumors, has been carrying out a similar experiment and came to this conclusion:
“I now have two years of data with my iPhone limited to an 80 percent charge, and I don’t think it’s been worth it.”
I agree, which is why I’m going back to 100% charging and instead using optimized battery charging, a feature that delays the charge from 80 to 100% so it happens in time for you to start the day (this feature takes a while to activate because it needs time for the handset to learn your patterns). This seemed to do more to reduce battery wear, at least on earlier iPhones I had. So, maybe this, along with the vapor chamber cooling, will keep my new battery going strong for longer.
I can hope.
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