Ask most people what they want in a new smartphone, and there are usually three key factors: a large screen, a great camera, and excellent battery life. Over the past decade, phones have gotten better, and the best phone cameras are better than most dedicated cameras, but battery technology has arguably not progressed as fast.
Yet, some companies are always trying to push the boundaries of what’s possible with smartphone batteries. New technologies such as silicon-carbon have yielded higher-density batteries — with some trade-offs in longevity — meaning phone makers can fit more capacity in the same space without increasing the phone's thickness.
We’ve seen a couple of concepts with 10,000mAh batteries, but the new Realme P4 Power is the first mass-produced smartphone with a battery this size that’s actually designed for customers to buy. I’ve spent a couple of weeks testing it, and this is how long this battery actually lasts.
Big battery without the big bulk
The Realme P4 Power is the first phone to use third-generation silicon carbon battery technology, and alongside these changes, it also ushers in a new era: one where phones with 10,000mAh batteries don’t need to be as thick as phones like Unihertz Tank 3, which has a 23,800 mAh battery but measures 30mm thick.
In comparison, the Realme P4 Power has a 10,001mAh battery but measures just 9.08mm. For context, that’s just 0.8mm thicker than the Find X9 Pro, which measures 8.3 mm and has a 7,500mAh battery, and 0.9 mm thicker than the Galaxy S25 Ultra, which measures 8.2mm but has a 5,000 mAh battery.
Now it’s worth noting that this is only one part of the puzzle: both of those phones have considerably better telephoto and ultrawide cameras than the Realme P4 Power, but the Realme P4 Power proves that we’ve entered the era where phones don’t need to be ultra-thick to have power-bank size capabilities. As we’ll see, that is an extremely apt comparison.
The Realme P4 Power is the smartest power bank ever made
I see two types of customers who are likely to buy the Realme P4 Power: people who use it every day as their main, or only, phone, or people who carry it as an alternative to a power bank. The latter is the core subject of this section, and in testing the Realme P4 Power over the past few weeks, one thing has become clear: this is the smartest power bank ever made.
First, unlike a regular power bank, this is a full smartphone, so it’s the ideal companion if you need a power bank on the go or a backup phone in case the worst happens. The 6.8-inch AMOLED display is vibrant, offers a 144Hz refresh rate — making it perfect for gaming — and at 219 grams, it’s incredibly light.
The main camera is a 50MP sensor with an f/1.8 aperture, but the 8MP ultrawide camera leaves a little to be desired. There’s also no telephoto or macro lens, but there is a color-sensing sensor that helps ensure accurate color reproduction in photos.
The 10,001mAh battery charges at 80W, but one key feature that sets it apart is 27W reverse charging, which lets it charge multiple phones at their maximum speeds or close to them. Recharging my iPhone 17 Pro's 3,998mAh battery took almost two hours and drained around 60% of the Realme P4 Power battery. Yes, there’s definitely some efficiency loss, but this is still an excellent power bank.
The Realme P4 Power is also an endurance champion
The theory has always been that a bigger battery will yield better battery life, but this hasn’t always been the case. Things like processor efficiency, camera use, gaming, and even calls can make a significant difference to battery life, but generally, a bigger battery offers greater endurance.
The Realme P4 Power has the best battery life I’ve ever experienced on a smartphone. With no usage, it lasts over two weeks even when connected to Wi-Fi and syncing notifications from a variety of apps.
With my normal usage, it lasted almost five days with over 20 hours of screen time. On one particular test, streaming video for around 12 hours on a flight from Hong Kong to London drained only 42% of the battery. Yes, not video playback from a preloaded file, but streaming via YouTube on a spotty internet connection that occasionally cut in and out.
The longest it lasted me was six days and 24 hours of screen time, while with heavy usage, it dropped to just over four days, which is still better than any other phone I’ve tried recently. On average, heavy use of the Realme P4 Power delivered over 13 hours of screen time, which is far better than any other mass-produced phone on the market right now.
The Realme P4 Power also charges fairly quickly
The Realme P4 Power is more than just an endurance champion, but if you’re used to Realme’s incredible history of battery innovations, you might find the 80W charging somewhat disappointing.
Compared to the 240W and 320W charging the company has offered in the past, 80W is much slower, but there’s a key reason for that: the desire to keep the phone relatively thin. Talking to Chase Xu, VP and CMO at Realme, he revealed that while it would have been possible to add these superfast record-breaking charging speeds to the P4 Power, it would have required a considerable tradeoff in thickness.
Instead, we have 80W, which is on par with the charging speeds offered by most Oppo, Realme, and OnePlus phones. It takes around 88 minutes to charge to full using the included 80W charger, which equates to 114mAh per minute. This is slower than its rivals' phones, which is to be expected given the battery's size. Meanwhile, a 36-minute charge takes the phone to 50% — or around 5,000mAh, the same capacity as the Galaxy S25 Ultra but in half the time.
The phone for those who care about battery
If battery life is your top priority, the Realme P4 Power is the phone to consider. It has the best battery life I've seen on a phone, and it lasts for days even with heavy usage. Even when the battery hits 5%, you can still use it for hours. While it’s not a replacement for the best smartphones, it does excite me about the future of smartphone batteries.
