A Chinese regulatory filing spotted by leaker Digital Chat Station suggests the iPhone 18 Pro Max could ship with a 5,567 mAh battery in the US — a 9.5% increase over the iPhone 17 Pro Max's 5,088 mAh cell. Earlier reports from February and June 2026 had pegged the increase at roughly 2%, citing figures between 5,100 and 5,200 mAh. The new number, if accurate, would mark the largest year-over-year capacity jump for a Pro Max model in recent generations.

The same filing shows the standard iPhone 18 Pro receiving only a marginal bump to 4,288 mAh from 4,252 mAh, reinforcing a widening gap between Pro and Pro Max tiers. Digital Chat Station, who provided both the old and new figures, has a sporadic track record and expressed skepticism about the Pro Max number in their Weibo post.

Separately, February rumors claimed the upcoming iPhone Fold would carry Apple's largest-ever battery, though no capacities were specified. The foldable's design constraints — dual displays, hinge mechanism — make battery engineering particularly challenging.

If the 5,567 mAh figure holds, the Pro Max could deliver meaningfully longer real-world runtime, especially for power users. But given the source's inconsistency and the leaker's own doubts, treating this as confirmed would be premature. The Pro model's near-flat capacity also suggests Apple is reserving major battery gains for its largest, most expensive handset.