It may not be regarded as the flagship of the iPhone range as of this fall (that honor will transfer to the folding iPhone Ultra), but this year’s Pro Max model will have at least something to boast about: one of the biggest batteries ever to grace an iPhone. That’s if a new report is accurate, at any rate.
According to a leak on social media this week, the iPhone 18 Pro Max will have a battery capacity of 5,235 mAh on the Nano SIM model and a whopping 5,425 mAh on the eSIM-only version. That’s an increase of 8.5 percent and 6.6 percent, respectively, compared to the 4,823 mAh/5,088 mAh capacities of the iPhone 17 Pro Max models.
Those are solid year-over-year bumps, though not among the biggest we’ve seen. Last month, we heard that the iPhone 18 Pro will only go up by 1.5 percent and 0.8 percent across the two models, compared to previous annual increases of up to 19 percent.
But in absolute terms, compared with phones outside the Apple bubble, these would be impressive figures. In the past, Apple’s phones were often criticized for their relatively small batteries, but 5,425 mAh would stand comparison with most rival offerings. The Samsung Galaxy S26 Ultra, for example, has a capacity of 5,000 mAh.
iPhone battery capacities have been rising steadily for the past few generations. Here’s how the rumored figures compare with the previous five Pro Max models:
- iPhone 13 Pro Max: 4,352 mAh
- iPhone 14 Pro Max: 4,323 mAh
- iPhone 15 Pro Max: 4,441 mAh
- iPhone 16 Pro Max: 4,685 mAh
- iPhone 17 Pro Max: 4,823 mAh (Nano SIM), 5,088 mAh (eSIM only)
- iPhone 18 Pro Max: 5,235 mAh (Nano SIM, claimed), 5,425 mAh (eSIM only, claimed)
Is this report legitimate?
The key question about all this is, as with most iPhone rumors, whether this report can be trusted. That’s debatable. Even tracing its origin is complicated.
We first saw it covered by the reputable news site GSMArena, which linked to a since-deleted tweet by a leaker going by the handle @fireuniverse8. However, we’ve found this still-available tweet, which appears to contain largely the same information: Two batteries that seemingly belong to the iPhone 18 Pro Max, labeled with corresponding battery capacities.
With us so far? Good.
We can’t see the image from the original tweet, which may have named a source in the form of a watermark or similar. But we can still see the accompanying text: “Even iPhone 18 Pro Max battery higher than S26 Ultra,” which matches up with the numbers in a general sense. But that doesn’t give us much to go on, or reason to believe it’s legitimate.
The remaining tweet, meanwhile, contains a screenshot of a post on Weibo that appears to come from an entirely different person. Using Google Translate, their account name comes up as “Doge Internet Technology,” and the avatar is different. Is this the original source? Or, as seems more likely, is this a follower of Fire Universe discussing the information disclosed in the previous tweet, and Fire Universe then reposting that?
(If you’re interested, Doge’s commentary reads: “The world has suffered from SIM cards for too long. iPhone 18 Pro Max Battery. Compared to the overseas eSIM version, it has 190 mAh less battery life. What will it use to compensate?”)
Fire Universe isn’t a leaker we’re familiar with, so we don’t have a track record to check. So what that leaves us with is a leaker without much of a reputation posting a rumor without a source, or repeating a rumor from another unfamiliar leaker, then deleting the tweet, but leaving up a tweet where we can still see the numbers. Hopefully that’s all clear.
Under normal circumstances, we’d advise extreme skepticism with something like this, but the one point in its favor is the fact that other sources have previously predicted something similar. In February, another Weibo leaker (one who is more familiar to the rumorsphere, Digital Chat Station) claimed the 18 Pro Max would have battery capacities of roughly 5000mAh and 5100-5200mAh, respectively. The latest numbers are more optimistic, but largely align with the original claim.
One final note: there’s a reason why I said one of the biggest batteries ever to grace an iPhone. The iPhone Ultra is expected to have a battery capacity of around 5,500mAh, and could go as high as 5,800 mAh. That would be really big and one of the largest ever—the Galaxy Z Fold 7, for example, only uses a 4,400mAh battery, and the latest iPad mini has a 5,078 mAh battery. But that’s why it’s going to be the flagship–and why it could cost as much as $2,500.
