iOS 18 Lets You to Set the Maximum Charge Limit on Your iPhone Below 100%. It Makes Perfect Sense

  • One of iOS 18’s new features allows you to limit the your battery's maximum charge to between 80% and 100%.

  • It’s an exciting tool to optimize your phone’s charge and increase battery life.

iOS 18 on iPhone 15
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iOS 18 is almost here. We’ll have to wait until the presentation of the iPhone 16 to try out the definitive version of this operating system on the iPhone Xs and above. However, the iOS 18 developer beta is already available, and you can test it—which isn’t recommended, at least on your main phone. Apple unveiled many new features at WWDC 2024, but there was something that it didn’t mention, and it's actually really useful: the ability to set a maximum charge limit.

What does that mean? Let’s start at the beginning. A battery's lifespan is one of the most critical aspects of any device. This goes beyond phones and applies to tablets, smartwatches, and even electric cars. When it comes to batteries, the lifespan is measured in cycles. The more cycles the battery offers, the more time you have before it starts to degrade excessively, losing capacity and, therefore, offering less autonomy.

What is a cycle? When you charge 100% of the battery, you complete a cycle. Charging it from 0% to 100% is a cycle. Charging it 20% today, 40% tomorrow, and 40% the day after is a cycle. It doesn’t matter how you do it. When the total is 100, a cycle is complete. Now, batteries can support a certain amount of cycles before they start to lose power. A battery with 10 cycles will provide more autonomy than 600 or 1,000. This is what's referred to as “battery health.”

If your phone is old and you've never changed the battery, you might notice that it's slow and has much less autonomy. This is why. The cycles add up, the battery deteriorates, the autonomy worsens, and the device adjusts its performance to maintain a power/autonomy ratio that allows us to avoid charging the phone every two hours. Other factors are at play, but this is one of the main issues.

USB-C port on an iPhone 15 Pro Max USB-C port on an iPhone 15 Pro Max. Image | Xataka On

The 20/80 rule. How can you optimize device charging to extend your battery's life? With good charging habits. Experts tend to recommend two: First, avoid fast charging if you don’t need it. And second, keep the battery charged to between 20% and 80%.

A study states that a battery's most critical zones are 0-20% and 80-100%. Charging in these ranges increases battery degradation, requires more power, and generates more heat. In short, charging the phone when it’s about to shut down or keeping it charged longer than necessary can work against us.

The Problem. These habits require some commitment. If you want to keep your phone charged between 20% and 80%, you have plug it in and unplug it on time. The first step is effortless, but the second is another story. Putting your phone to charge before it drops below 20% is easy, but if you're in the habit of charging it at night, no one is going to get up at four in the morning to unplug their phone once it reaches 80%.

Screenshots showing the option to set a charging limit in iOS 18. It's now possible to set a charging limit in Settings in iOS 18.

The solution. If you enable optimized charging on iPhones, the battery will charge up to 80% and only charge to 100% when the phone thinks you're waking up. Now, with iOS 18, you can go even further: You can limit the maximum charge to 80%. That way, when you charge your iPhone, it automatically stops charging when it reaches that percentage, something that Samsung, Huawei, OPPO, Realme, and Sony phones can already do.

This feature arrived recently with iOS 17, but with iOS 18, the system goes a little further, as you'll see below. Combining the low battery notification (which pops up when your phone reaches 20%) with the 80% charge limit and the slow charge will help you to have healthier charging habits.

Surviving with 60%. There is a downside of this habit: It limits you to 60% of battery for the day, which not all phones can permit, especially if you use them intensively (e.g. setting maximum brightness, running with GPS, playing games, recording videos). Ultimately, you have balance the two options and decide based on your needs. You can also be proactive and turn off the limit when you know you have to use your phone intensively that day.

In that sense, Apple’s approach is interesting because it allows you to set the limit at 80% and jump from 5% to 100%. If you see that you're a little short at 80%, you can adjust the limit to 90%. The idea is to reduce the time the phone spends in those two critical areas for its battery.

Images | Xataka

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