Earlier today I saw a post from someone who has had their iPhone stop charging at 80% for the past year and they didn’t see much, if any difference in battery health than their coworkers who didn’t do anything, and let the iPhone do its “optimized charging” over the past year. I remarked on social media:

I think a lot of people feel like they need to baby their devices as if they’re Windows XP laptops from 20 years ago. The beauty of modern mobile operating systems is that they take care of things like battery performance for you.

Capping your battery charge to 80% doesn’t improve longevity, it just means you never get to experience the full battery life of the phone you bought.

In retrospect, I think my second sentence is a bit more assertive than I would say my opinion actually is, but I am very interested to see what the differences are in iPhone battery life between those that limit charging and those that let the OS do its thing. Everything I’ve seen indicates to me that the benefits to battery health are so minor as to be within the margin of error.

But let’s say I was someone who planned on using their iPhone for 4 years and wanted to make sure I had the best battery experience possible over that time period. Should I limit my charge to 80% or should I let the OS manage it for me? Well, I’d like to see some data on this to know what the right decision is for me. The challenge for me is that there isn’t much data out there. Additionally, I just got off 70-some hours of battery testing myself, so I am more aware than most about how fickle battery comparisons can be.

By the way, the screenshot at the top of the post is from my iPhone 15 Pro, which I used most of the last year, and I did not change any of the system settings for battery life. It spent half the year as my main phone and was actively used, and the other half of the year it sat on a charger most of the time. It currently reports its battery health as 100%.

Now let’s say that we do actually get some data that shows that over time, limiting your battery charge to 80% does cause battery health to drop slower. Now the question becomes how long does it take for me to start coming out ahead? I’m immediately sacrificing 20% of my battery’s performance on day one, so I think we can all agree that for the first part of setting this limit, I’m getting worse battery life than everyone else who lets their phone go to 100%. Kind of like how solar panels are a massive up-front cost that eventually start turning you a profit a decade down the line, when is the point that my 20% sacrifice starts to pay off? 2 years? 3 years? 5 years?

Also, one would presume that someone who caps their battery at 80% would continue capping it there forever, so it’s not just that this needs to save battery health a little faster, it needs to save it a lot faster. If I’ve capped my charging and I’m at 80% health 3 years later, and I would have been at 70% health if I’d used iOS’s optimized charging, then I’m still getting worse actual battery life since I’m not getting that 80%, I’m getting closer to 64% since I’m not letting it use the full capacity now either. This gets back to the data problem because we don’t really know.

What I’m really getting as it that if I was going to cause an intentional and significant reduction in my brand new iPhone’s battery’s capacity, then I’d definitely want to know when I would start reaping the benefits. If it doesn’t really help at all, then I’d want to know that as well so that I could make the rational decision of letting iOS do what it wants with optimized charging so that my phone experience was better.

If you cap your iPhone’s charging to 80% or some other lower number, I am not telling you to stop. If you want to do it, go ahead, it doesn’t impact me so carry on. What I will say is that the first line of my social media post is something I believe:

I think a lot of people feel like they need to baby their devices as if they’re Windows XP laptops from 20 years ago.

I think a lot of people feel like they need to baby their phone more than they do. Apple introduced optimized charging several years ago, which does quite a bit to play with charging behaviors so that it helps avoid the problems caused by things that used to hurt laptops. Like I said, if you do it and like it, carry on, but do with eyes open and knowing what trade-offs you’re making. If anything, this is a call for any and all data that can be collected on how beneficial capping your charging is on iPhones. If more people would benefit from turning this on, I want to know! If people are just making a worse iPhone experience for themselves, I want to know as well! We can disagree about whether we think it’s worth it for each of us individually, but it would be great to have a baseline of data to work from here.