Information from Instant Digital, a well-known Weibo account with over 1.4 million followers and a strong track record of Apple-related leaks, reveals that the iPhone 17 Air – also referred to as the "iPhone 17 Slim" – will have a battery capacity of around 2,800 mAh.

This is relatively low compared to Android smartphones, which often exceed 4,000–5,000 mAh, and even lower than some previous iPhone models like the iPhone 14 Plus (4,325 mAh).

However, Apple believes the iPhone 17 Air can still last a full day thanks to iOS 26’s new “Adaptive Power Mode,” which intelligently manages power usage and optimizes performance based on real-time scenarios.

Why the battery is smaller

The main reason for the reduced battery size is the ultra-thin 5.5mm design of the iPhone 17 Air, making it the slimmest iPhone ever produced – even thinner than the last-generation iPod Touch.

While the sleek design lends a futuristic and premium aesthetic, it sacrifices internal space for the battery and other components.

As a result, Apple is looking to optimize power through software and is developing a dedicated battery case as a hardware workaround.

According to a report from The Information, Apple is working on a battery-integrated case specifically for the iPhone 17 Air. This accessory would not only extend battery life but also offer added physical protection.

Apple previously released battery cases for the iPhone 11 and MagSafe Battery Packs for the iPhone 12 and newer but discontinued them in 2023.

The revival of a battery accessory suggests Apple is acknowledging the challenge posed by ultra-thin designs in meeting power demands.

Is under 3,000 mAh enough for a full day?

According to internal Apple tests (leaked by The Information), about 60–70% of iPhone 17 Air users can expect all-day usage without needing a midday charge. For comparison, this figure is 80–90% on other iPhone models.

This gap suggests the iPhone 17 Air targets office users, casual users, or those who value design – rather than gamers, content creators, or power users.

iPhone 17 Pro Max: Apple’s biggest battery yet?

The iPhone 17 lineup is expected to include four models: iPhone 17 (standard), iPhone 17 Air (thin and light), iPhone 17 Pro, and iPhone 17 Pro Max.

Rumors suggest the Pro and Pro Max versions will feature significantly larger batteries, ranging from 3,800 to nearly 5,000 mAh, thanks to larger device dimensions.

A post from Instant Digital on Weibo claims the iPhone 17 Pro Max will house a battery close to 5,000 mAh – the largest ever on an iPhone.

While the 5,000 mAh figure is likely an approximation, it marks a clear upgrade. For comparison:

iPhone 14 Pro Max: 4,323 mAh
iPhone 15 Pro Max: 4,422 mAh
iPhone 16 Pro Max: 4,676 mAh

A nearly 5,000 mAh battery would be about a 10% increase over the iPhone 16 Pro Max.

Larger batteries typically improve usage time, but the gain isn’t always linear. Earlier this year, another credible leak noted that the iPhone 17 Pro Max would be 8.725mm thick, up from 8.25mm on its predecessor.

This minor thickness change could accommodate about 400 mAh more battery capacity. The overlap between sources makes the leak more plausible.

iOS 26’s Adaptive Power Mode: The secret weapon

Apple is betting on iOS 26 to enhance battery efficiency without increasing physical capacity.

The new Adaptive Power Mode reportedly offers:

Usage-based energy optimization based on user behavior
Automatic underclocking and screen dimming during inactivity
Smart background task management based on app priority

If it performs well, the feature could make smaller batteries “smarter,” delivering real-world usage similar to phones with larger batteries.

A new design philosophy for iPhone 17

With the iPhone 17 series – particularly the iPhone 17 Air – Apple is embracing a new design philosophy: minimalist, lightweight, and futuristic.

But the sleek design comes with trade-offs. Rather than ignore these, Apple is investing in smarter software (iOS 26), helpful accessories (battery cases), and more efficient internals (such as the A18 chip).

This strategy aims not only to extend battery life but also to redefine how users perceive battery performance – shifting from mAh metrics to actual daily usability.

Meanwhile, the iPhone 17 Pro Max is shaping up to satisfy Apple’s high-end audience with a significantly upgraded battery.

Consumers will have to wait until September to find out if the iPhone 17 Air’s ultra-thin design is worth the battery trade-off. But the iPhone 17 Pro Max is already turning heads with upgrades that could win over power users.

Hai Phong (The Information, AppleInsider)