Should you not fully charge your phone?


The smartphone battery limit debate

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Battery protection settings on a Samsung phone

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Last year, I wrote about how to limit the maximum charge on your phone to preserve its long-term battery health, but should you? That’s recently become a topic of geeky debate.

Smartphone batteries naturally lose the ability to hold a charge over time, but they degrade faster when the phone is kept at a full charge, and are healthiest when the charge level stays between 20% and 80%. While most phones have built-in ways to minimize the stress caused by overnight charging, newer iPhones (15 and higher) and Samsung phones go a step further, letting you set maximum charge levels as low as 80%.

Now, a couple of publications have tried to quantify whether depriving yourself of a full charge is worth the long-term battery health benefits. The short answer: Probably not, though it depends how you use your phone and how long you intend to keep it.

The evidence

Charging options on the iPhone 15 and newer

Let’s start with this Macrumors story by Juli Clover, who spent the last year limiting her iPhone 15 Pro Max’s charge level to 80%. One year and 299 charging cycles later, Clover’s phone showed a maximum capacity of 94%. (The phone still charges to 100%, but shows a diminished capacity level under Settings > Battery > Battery Health.)

By comparison, a couple of other Macrumors staffers who didn’t limit their iPhone 15 Pro Max batteries had capacity levels of 87% (after 329 charge cycles) and 90% (after 271 cycles).

It’s worth noting that Clover often let her battery “get quite low before charging,” which itself can be detrimental to battery health. Even so, capping the charge seems to have kept Clover’s battery healthier by at least handful of percentage points over a one-year span.

Meanwhile, Macworld’s German counterpart Macwelt took things a step further, asking its Facebook audience to submit screenshots of their iPhones’ battery health along with descriptions of charge behavior. The results were less pronounced than those of Macrumors, showing an average 1% to 2% improvement in battery health over a year, though the site still concluded that limiting the charge level has a “statistically significant influence on battery health and longevity.”

Drawing conclusions

Over at Daring Fireball, John Gruber argues that the gains aren’t significant enough to justify limiting your phone’s maximum charge.

All you’re doing is preventing yourself from ever enjoying a 100-percent-capacity battery. Let the device manage its own battery. Apple has put a lot of engineering into making that really smart.

That’s a valid viewpoint for folks who upgrade at least once every few years, especially if it involves trading in the old phone through a device maker or wireless carrier. Still, it doesn’t capture some edge cases where limiting the charge level might make sense:

  • Are you buying a used or refurbished phone? While this can be a great way to save money, you’ll be starting out at diminished battery health compared to buying new, so you may want to take extra steps to preserve what’s left.
  • Do you sell your own phones? Device makers and wireless carriers generally don’t ask about the battery health of your trade-in, but individual buyers might. The marketplace site Swappa even requires sellers to disclose iPhone battery health levels, so preserving battery capacity may lead to better resale value.
  • Do you use StandBy mode? This iPhone feature turns your phone into a smart display when it’s charging and turned on its side, showing a clock, photos, and customizable widgets. Limiting the charge level can prevent this feature from stressing your battery. (Same goes if you use the Screen Saver mode on Android phones.)
  • Are you keeping your phone for more than a few years? Without adequate care, a phone’s battery health could eventually drop below 80%, and you may even notice a decline in performance as the battery degrades. Being mindful of charge capacity now could yield benefits in those later years.
Automating battery modes on a Samsung phone

Note that on Samsung phones, you can automate battery modes using the Routines feature. I’ve set up an 80% limit for my Galaxy Z Fold5 on weekdays, and it switches over to getting a full charge on weekends when my usage increases.

As for my new iPhone, I’ve decided to run an experiment of my own: I’m going to cap the charge level at 80% just to see what happens. If it gets too annoying, I’ll switch back to the default Optimized Battery Charging mode. But if I never feel the squeeze, then I’ll be glad to have stretched the battery’s lifespan a bit further—whether it’s for me or whoever owns my phone in the future.


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Jared