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Oppo Find X9 and Honor Magic8: Large batteries that are getting smaller in Europe
by Jan Johannsen
OnePlus 15 tested: the 24-hour smartphone
19.11.2025
Translation: machine translated
Pictures: Jan Johannsen
The OnePlus 15 offers a very large battery capacity and is still not bulky. 24 hours of continuous use is no problem. The top smartphone is also impressive beyond the battery.
With the OnePlus 15, a manufacturer is finally using a new battery technology to increase battery life. The smartphone can be used for longer than I can stay awake and offers plenty of performance, a good camera setup and one or two gimmicks.
Silicon carbon makes battery dreams come true
Silicon-carbon batteries can store more energy in the same volume than conventional lithium-ion batteries. So far, manufacturers have mainly used the new technology to reduce the size of the batteries while maintaining the same capacity - to make more space for other components or to make the smartphone thinner.
The OnePlus 15 is different. BBK, the company behind the brand, has not reduced the volume of the two built-in batteries and has achieved a capacity of 7300 mAh. For comparison: The Samsung Galaxy S25 Ultra has over 5000 mAh - no relevant top smartphone has over 6000 mAh. And yet, at 8.1 millimetres, the OnePlus 15 is 0.1 millimetres thinner and three grammes lighter than the S25 Ultra.
OnePlus is not alone in setting this trend. Chinese manufacturer Honor has also broken the 7000 mAh barrier with the Magic 8 Pro, but has already announced that it will only be sold with 6270 mAh in Europe.
Back to the OnePlus 15, it is the first smartphone to last over 24 hours in my PCMark battery test at half display brightness. To be precise: 24 hours and 34 minutes. Not only does that easily get me through the day, but depending on my usage behaviour, I can even manage two days. However, it's more realistic that I'll reach for the charging cable at some point during the next day.
The OnePlus 15 accepts up to 120 watts when charging if the power supply supports the SuperVooc fast charging technology from OnePlus and Oppo. This means that the large battery is fully charged in around 40 minutes and already half charged after a quarter of an hour. With wireless charging, up to 50 watts are possible with a suitable charger.
Those who want to use the OnePlus 15 with a charging cable will be pleased with the bypass power supply. This ensures that the battery does not heat up as much as usual. Put simply, the power is sent around the battery directly to the point of use.
Speaking of heat: The «Glacier Back Cover» on the back is designed to dissipate heat at all times, regardless of the charging process, thus preventing temperature-related throttling of the hardware. Small disadvantage: The back is sensitive to «scratches». However, these are sometimes so light that they can be wiped away again. However, this does not inspire confidence in a long-term clean appearance.
Latest chipset with plenty of computing power
BBK relies on the new Snapdragon 8 Elite Gen 5 for the OnePlus 15. Qualcomm's currently most powerful chipset outperforms all other processors in the Android sector.
My test device is the version with 12 gigabytes of RAM and 256 gigabytes of storage space. There is also a more expensive version with 16 and 512 gigabytes.
One button for the AI or other
With «Plus Key», the OnePlus 15 has an extra button on the left-hand side - opposite the power button and volume control. This is linked to the «Mind Space» by default. This is a place to collect screenshots and voice memos, which are then managed and processed by an AI. Nothing offers something similar with «Essential Space».
I press the Plus Key button to take a screenshot and save it in Mind Space. If I hold down the button, I can record a voice memo, which also ends up in the Mind Space. Double-click to open the Mind Space.
I can change one of these three actions. Instead of a voice memo, I can assign a different function to the long press. The following are available:
- Change sound and vibration
- «Do not disturb» switch on and off
- Activate camera
- Switch torch on and off
- Start recorder
- Open translation tool
- Take a classic screenshot
As I do not use such AI collections, I would also like to change the other actions of the Plus Key. However, this is not possible in the settings of the OnePlus 15.
50-megapixel trio for good photos
The OnePlus 15 has three 50-megapixel cameras on the back, which differ in terms of focal length, aperture and sensor size. The telephoto camera offers 3.5 times the focal length of the main camera and the front camera stands out with its 32 megapixel resolution:
- Main camera: 50 megapixels, 1/1.56 inch, f/1.8, 24 mm
- Ultra wide-angle camera: 50 megapixel, 1/2.88 inch, f/2.0, 16 mm
- telephoto camera: 50 megapixel, 1/2.76 inch, f/2.8, 85 mm
- Front camera: 32 megapixel, 1/2.74 inch, f/2.4, 21 mm
The OnePlus 15 adopts the algorithm for image composition from the top smartphones of its sister brand Oppo.
All three cameras impress with a high level of detail. There are differences due to the apertures and sensors, especially in the dark, but these can be compensated for by the longer exposure time of the night mode.
The colour reproduction is not overly bright, but still intense and natural.
Contrasts and sunshine are not a problem for either the main or the ultra-wide-angle camera.
The telephoto camera brings subjects closer - without compromising on image quality.
The telephoto camera is not as perfect, but still very good in the dark. It is worth using the night mode here. This does not simply brighten the image, but ensures that lamps and other illuminated objects are not overexposed. The atmosphere of the night is retained.
With the ultra-wide-angle camera, the images remain very dark at night. Night mode provides more brightness overall.
In contrast, I find it difficult to recognise a difference between the conventional automatic mode and night mode on the main camera.
The selfies look very good during the day. The only challenge is in the dark. Night mode brings minimal improvements here, especially with light sources.
Beautiful display
For viewing your photos and other things, the OnePlus 15 has a 6.78-inch AMOLED display with a resolution of 2772 × 1272 pixels. This results in a pixel density of 450 ppi and therefore a sharp display. The colour reproduction is vivid and natural. The brightness of 800 nits is sufficient for outdoor use in sunshine. At its peak, the screen reaches up to 1800 nits. Other smartphones offer higher values, but the peak brightness is only utilised for HDR content.
The refresh rate automatically adjusts to the content between 1 and 120 Hertz to ensure a smooth display. You can also set 165 Hertz manually. However, this only makes sense when playing games.
OxygenOS 16 with some AI tools
OxygenOS 16, which is based on Android 16, runs on the OnePlus 15 ex works. The manufacturer currently supplies its devices with four new Android versions and provides security updates for six years. The few pre-installed apps from third-party providers can be quickly deleted.
Gemini is pre-installed as an AI assistant. In addition to the aforementioned Mind Space, OnePlus also offers three other AI functions of its own. «AI author» edits texts or comes up with completely new ones, for example for images that you want to post. «AI translator» helps when it comes to understanding foreign languages and «AI-VoiceScribe» records voice notes, summarises things and can also translate.
With the «Zen Space» I can switch off the OnePlus 15 so that I'm not distracted. Thanks to the built-in infrared sensor, I can set up the smartphone as a universal remote control for a wide range of devices using the «IR remote control app».
In a nutshell
Top smartphone with very long battery life
The OnePlus 15 has a very good camera setup, a stylish display and plenty of computing power. Its large battery sets it apart from other top smartphones. This does not make the smartphone any heavier or thicker, but ensures a very long battery life.
In the end, there are only small details to criticise. I would like to assign other functions to the extra button and have one more Android version as an update. But that's all complaining on a high level. The scratch-sensitive back could prove to be a bigger problem in the long term.
Pro
- Large battery and very long battery life
- Very good camera setup, incl. telephoto camera
- A lot of computing power
Contra
- Plus Key cannot be completely separated from AI functions
- Only four Android updates
- Sensitive back
Smartphones
CHF899.– with free promotional product
OnePlus 15
512 GB, Ultra Purple, 6.78", Dual SIM, 5G
Header image: Jan Johannsen
Jan Johannsen
Senior Editor
Jan.Johannsen@galaxus.deAs a primary school pupil, I used to sit in a friend's living room with many of my classmates to play the Super NES. Now I get my hands on the latest technology and test it for you. In recent years at Curved, Computer Bild and Netzwelt, now at Digitec and Galaxus.
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