5 Used iPhone 15 Upgrades You Should Be Making the Most Of

The iPhone 15 series arrived with plenty of anticipation, and since its release, users have been discovering just how many hidden features and clever upgrades Apple packed into the device. While the new design and performance improvements naturally grab attention, it’s often the smaller features that make a real difference in daily use. At Used Mobiles 4 U, we’ve taken a closer look at five of the iPhone 15’s most practical features—things that can genuinely help you take better photos, protect your battery, and get more value from your device. Whether you’re buying brand new or considering a used iPhone 15, these features will ensure you get the most from your purchase.

1. Switch Up Camera Resolution

One of the standout improvements in the iPhone 15 series is the upgraded 48-megapixel main camera sensor. By default, the phone captures images in 24 megapixels, which Apple sees as the sweet spot between stunning image quality and manageable file size. For most people, this strikes the right balance, giving photos enough sharpness for cropping and editing without eating up too much storage. If you’re buying a used iPhone 15, this camera system ensures you’re still getting flagship-level photography at a more affordable price.

However, what makes the camera so flexible is that you can adjust the resolution to suit your own needs. If you’re running low on storage, you can drop the resolution to 12 MP in Settings > Camera > Formats, which is still more than enough for social media posts or casual snapshots. On the other hand, if you want to unleash the full power of the camera, you can enable “Resolution Control” or even shoot in Apple’s “ProRAW” format. ProRAW files give professional photographers maximum editing flexibility, capturing more colour and detail, but they do take up significantly more space.

The introduction of the HEIF format also helps users save storage, as it compresses photos without noticeably reducing quality. So whether you’re a casual user who wants convenience or an enthusiast who edits photos in detail, the iPhone 15 gives you total control over your camera resolution. For anyone upgrading from older iPhones—or looking at a used iPhone 15—this level of flexibility will feel like a real step forward.

2. Set a Smart 80% Charge Cap

Battery health has always been a hot topic among iPhone users, and Apple has finally given us a simple but powerful way to manage it. One of the best new features on the iPhone 15 is the ability to set a permanent 80% charge cap. Why is this so useful? Because lithium-ion batteries naturally degrade over time, and repeatedly charging your phone to 100% accelerates this process. Keeping your battery between 20% and 80% is widely recognised as the best way to extend its overall lifespan. With a used iPhone 15, this becomes even more important, as protecting battery health ensures longer-lasting performance.

With the iPhone 15, this practice becomes effortless. You can head to Settings > Battery > Battery Health & Charging > Charging Optimisation and choose the 80% limit option. Once this is enabled, your iPhone will automatically stop charging beyond that point. This means no more waking up in the morning with your battery sitting at 100% after hours on charge. Instead, the phone intelligently protects itself, giving you peace of mind that your battery will last longer before needing replacement.

This feature is especially valuable for people who like to keep their devices for several years or who are thinking about purchasing a used iPhone 15. By reducing the wear on the battery, you’re ensuring smoother long-term performance and saving yourself the cost and hassle of battery replacements.

At Used Mobiles 4 U, we know how important battery life is to our customers. That’s why we think this subtle feature makes the iPhone 15 one of the most future-proof options available. It’s a small change, but it can make a huge difference to the way you use your used iPhone 15 every day.

3. Monitor Battery Cycle Count Easily

In the past, checking your iPhone’s battery cycle count was something only tech-savvy users could do—often requiring third-party apps or connecting to a computer. The cycle count is important because it tells you how many full charge cycles your battery has gone through, giving you an accurate picture of how much life it has left. A cycle is counted when you use the equivalent of 100% of the battery, even if it’s across multiple charges. For example, charging from 50% to 100% twice equals one full cycle. For anyone buying a used iPhone 15, being able to check this directly is a huge advantage.

Now, with the iPhone 15, Apple has finally made this information accessible right inside the phone’s settings. By heading to Settings > General > About, you’ll find a new “Battery” section that displays key details such as the battery’s manufacturing date, the first date it was used, and its total cycle count. This transparency is a real win for users who want to understand their device better.

Why does this matter so much? Because it allows you to make smarter decisions. If you’re wondering whether your battery is underperforming, you can compare its cycle count against Apple’s expected lifespan. Typically, iPhone batteries are designed to retain up to 80% of their original capacity after 500 complete cycles. With this data, you’ll know if it’s time to book a replacement or if your used iPhone 15 still has plenty of life left.

This is also particularly useful if you’re buying refurbished. Being able to check the cycle count yourself means you know exactly what you’re getting in terms of battery health. It gives users more confidence and makes a used iPhone 15 even more appealing as a reliable option.

4. Enjoy High-Quality External Display Output

One of the most underrated but exciting upgrades with the iPhone 15 is the improved external display capability. Thanks to Apple’s move to USB-C, the iPhone 15 can now output video in stunning 4K at 60 frames per second when connected to a compatible display. That means smoother visuals, sharper details, and more professional-level performance for anyone who connects their phone to a monitor, TV, or projector. If you own a used iPhone 15, this is a feature that can make it feel every bit as modern as a brand-new flagship device.

To take advantage of this, you’ll need a USB-C 3.1 or Thunderbolt 4 cable—but once connected, the difference is clear. Imagine streaming videos on a big screen without losing quality, sharing a presentation with colleagues directly from your phone, or even connecting to an external monitor for editing photos and videos. For creative professionals, this is a game-changer.

This is also a major step forward from the old Lightning connector, which had more limited bandwidth and couldn’t support the same high-quality output. The adoption of USB-C makes the iPhone 15 much more versatile, especially for people who like to use their phone as a hub for entertainment and productivity.

It’s not just about visuals, either. The connection is smoother and faster, with less lag when mirroring or streaming content. This makes a used iPhone 15 one of the best devices for both work and play. If you’re upgrading from an older iPhone, you’ll instantly notice how much more seamless it feels to connect to external displays.

5. Reverse Charging Made Simple

Perhaps one of the most practical features to arrive with the iPhone 15 is reverse charging via USB-C. This means your iPhone is no longer just a device that needs power—it can now give power to others. Whether it’s topping up your AirPods, giving your Apple Watch a quick boost, or even sharing a little charge with a friend’s device, the iPhone 15 makes it easy. If you’re carrying a used iPhone 15, you’ll find this feature incredibly handy for everyday life.

For years, Android users have had access to reverse charging, so Apple joining the party is welcome news. What makes this especially useful is how seamless it is. All you need is a compatible USB-C to USB-C cable, and your iPhone will automatically start charging the connected device. No settings to tweak, no apps required—just plug and go.

This feature is particularly handy when you’re on the move. For example, if you’re travelling and your AirPods case runs out of charge, you don’t need to hunt down a separate cable and charger. You can simply use your used iPhone 15 to get them powered back up. It transforms your phone into a mini power bank, reducing the need to carry extra gadgets around.

From a practical standpoint, reverse charging adds genuine convenience to everyday life. It shows how Apple is focusing on making the iPhone 15 more versatile and useful in real-world scenarios. For users considering a used iPhone 15, it’s another reason to make the switch—because it’s not just about premium features, but about practical tools that make life easier.