When I first saw that the Oppo Find X9 Pro had a whopping 7500mAh battery, I wasn’t that excited.
You see, Chinese manufacturers do tend to put frankly massive batteries within their phones – but only in China.
Due to EU regulations on the capacity of a single battery within a smartphone, phones available in Europe – and yes, despite Brexit, this also applies to the UK, given that most cargo goes via Europe – have a smaller overall capacity.
Of course, there are ways around this limitation; manufacturers can use a dual-cell design, allowing them to increase the capacity beyond the 5000mAh capacity seen in most phones in 2025 – but that requires manufacturers to either adopt the same dual-cell design in China or design a totally different system for international users.
Usually, it’s the latter, with China-focused phones getting huge, single-cell batteries, while international users get a smaller single-cell battery in line with EU regulations.
So, with that in mind, I fully expected that to be the case with the frankly massive 7500mAh battery capacity with the Oppo Find X9 Pro – but that’s not the case. That massive 7500mAh cell is available internationally.
For context, even phones like the Samsung Galaxy S25 Ultra offer the same 5000mAh cell we’ve seen for years at this point. It’s a great capacity for a big-screen phone, but as I’m sure we’ve all experienced, 5000mAh cells don’t always get you through the busiest of days.
But with a 40% bigger capacity than the S25 Ultra, I had very high hopes for the Oppo Find X9 Pro and its battery life. And, reader, I was impressed, but oddly enough, also a little bit disappointed.
Battery life is great – but it’s still a phone I charge every day
As you might expect from a phone with a battery 40% larger than Samsung’s top-end flagship, battery performance is very strong here.
It’s a phone that would make it through the day, no matter what I threw at it. Take a recent trip to Prague as an example.
On the first day of my trip, which saw the phone off charge for 20 hours on day one with near-constant use on my journey from home to the airport, on the two-hour flight and on the trip to the hotel, complete with plenty of WhatsApp messages and emails and snapping shots for my review, I still managed to finish the day with 30% left in the tank.
After using the Galaxy S25 Ultra as my main phone for months, I can confidently say that there’s no way it would’ve managed the same stint without me scrambling for my power bank.
Performance is even better if you’re a lighter phone user; on days when I’d work from home and only occasionally use my phone to reply to messages or scroll through social media, it wasn’t uncommon for me to go to bed with around 60% left in the tank.
So, yes, it easily offers some of the best battery life around right now, hands down. But, for me, I was expecting something more.
I decided to really push the phone to its limits and see just how long it could last on a charge, so one Sunday night, I didn’t put the phone on charge before I went into the office on Monday. I went to bed with 55% capacity remaining with around four hours of screen time, which led me to believe it’d get me through a full second day – but that wasn’t the case.
In fact, by the time I woke up seven hours later, the phone had drained by an additional 10% – despite it not being in active use during that time. Now with less than half my battery remaining, I wasn’t quite as confident as I was the night before – but there was still potential.
As the morning went on, however, my hopes started to dwindle. By the time it’d reached 11am, the phone had dropped to 30%, and by mid-afternoon, it neared the 20% mark – and that’s the danger zone in my mind, especially with a 100-minute commute home later in the day.
Adding to the anxiety was the fact that I was using Google Pay on the phone as my pass, so I had to have something left in the tank when I reached my destination.
It got to around 4pm and the phone had dropped to just 15%, at which point I conceded that it probably wasn’t going to be enough to get me home and quickly topped it up.
The fast charging meant I got back to 50% in around half an hour, which wasn’t all that long, and was more than enough to get me home and see me through the rest of the evening.
So, yes, for me, it doesn’t quite reach that coveted two-day use – and that was on a day when I didn’t have the full resolution active either, helping conserve a bit of battery life.
The Oppo Find X9 Pro has phenomenal battery life that’ll see you through the day, whether you’re gaming, binge watching shows or hammering social media – I just don’t think it has the two-day stamina that’s kind of expected when utilising such a high-capacity battery, at least with my average use.
Of course, there will be those who use their smartphone way less than I do, and there’s every possibility that it’ll indeed last a full two days without a charge, and maybe even longer.
But, what’s the point in having a phone with top-end processing power, incredible cameras and long battery life if you’re not going to utilise it? At that point, you might as well just buy the iPhone Air…
Size doesn’t matter; it’s how you use it
We’ve seen big increases in battery capacity from certain smartphone brands over the past couple of years. 2025’s OnePlus 13 has a 6000mAh cell, the Oppo Find X8 Pro has a 5910mAh cell, and the Motorola Edge 60 Pro has a 6000mAh cell – but again, even with these larger batteries, these are still comfortable one-day phones with my level of usage.
The problem doesn’t seem to be battery capacity, as Chinese brands have proven time and time again, but rather, it seems that optimisation is the real name of the game. It doesn’t matter how big the battery in your phone is; if components like the chipset and screen aren’t optimised, they’ll drain a lot of battery.
The best way to showcase how good optimisation can make all the difference is to look at Apple’s iPhone collection. iPhones have, hands-down, always had smaller batteries than their Android counterparts – but for the past few years, at least, they have competed or even surpassed higher-capacity Android alternatives in terms of day-to-day longevity.
The iPhone 14 Pro Max had a 4323mAh cell compared to the 5000mAh from the similarly sized Galaxy S22 Ultra, the iPhone 16 had a smaller 3561mAh cell than the likes of the 4000mAh Galaxy S24, and even the iPhone 17 Pro Max, Apple’s longest-lasting iPhone to date, has only just broken the 5000mAh barrier – and that’s only if you get the eSIM only variant. The SIM variant remains in the high 4000s.
Compared to the likes of the OnePlus 13 and Oppo Find X9 Pro, the iPhone 17 Pro Max’s battery performance pales in comparison, yet it still manages to put in a commendable showing. Most recent models of iPhone, regardless of size or battery capacity, tend to last the day with my level of usage – with the exception of the iPhone Air, of course.
While I’ve not yet used the iPhone 17 Pro Max, the iPhone 16 Pro Max was one of my favourite phones for a time because it was one of few phones that’d get me through a busy day with battery left to spare – and with a decent size increase with this year’s generation of iPhones, I’m confident that it could put on a similar performance to Oppo’s latest and greatest – despite having ~2500mAh less capacity.
So, yes, while bigger batteries are a net win for consumers who want better battery life, it’s not just about the size of the battery, but how well optimised your hardware is – and that’s where Android phones still need to improve.
