The official launch of the Galaxy S27 Ultra is drawing closer. Amid a growing stream of leaks, rumors and predictions surrounding Samsung's next flagship smartphone, one potential upgrade stands out as increasingly essential.

It is not the camera system, chipset, display or processor. These components have already reached a high level of refinement over recent generations. What Samsung really needs to improve is battery life.

Galaxy S27 Ultra battery upgrade after seven generations

Since the Galaxy S Ultra series debuted in 2020, one specification has remained virtually unchanged across seven generations: battery capacity.

The original Galaxy S20 Ultra came with a 5,000mAh battery. Remarkably, every successor has maintained exactly the same capacity.

Samsung has been particularly cautious about increasing battery capacity in its most premium flagship lineup. Some mid-range Galaxy A smartphones now offer comparable battery capacities and can even last longer thanks to their more power-efficient processors.

Meanwhile, competition from Chinese smartphone manufacturers is intensifying. Several models have already surpassed the 10,000mAh mark, while upcoming flagships such as the Xiaomi 18 Pro Max and OnePlus 16 are rumored to feature 8,000mAh and 9,000mAh batteries, respectively.

The widening battery capacity gap is making it increasingly difficult for Samsung to maintain its longstanding approach.

One reason Chinese smartphone makers can fit such large batteries into premium devices is silicon-carbon battery technology.

This technology incorporates silicon into the battery's anode to increase energy storage capacity. It allows manufacturers to achieve higher energy density without necessarily increasing the battery's physical size by the same proportion.

However, silicon-carbon technology comes with challenges of its own.

Silicon is relatively brittle and requires special protective coatings to help prevent the formation of branching structures known as dendrites, which can cause short circuits and damage batteries.

Another concern is that silicon can expand by 280% to 400% during charging, placing considerable stress on the battery's internal structure.

Nevertheless, silicon-carbon battery manufacturers have made substantial progress in addressing these limitations. Some technologies now support silicon-rich anodes containing up to 15% silicon. The Xiaomi 17 is even reported to use a battery with approximately 16% silicon content.

These advances give smartphone manufacturers an opportunity to significantly increase battery capacity without making major compromises in device design.

Samsung has begun testing silicon-carbon batteries

Samsung has not entirely stayed on the sidelines of this technological shift. The company has taken a cautious step toward silicon-carbon batteries with its Galaxy Z Fold 8 lineup.

In particular, the Galaxy Z Fold 8 Ultra features a 5,000mAh battery, up from 4,400mAh in its predecessor.

While this is not a particularly dramatic improvement compared with the potential of silicon-carbon technology, the Galaxy Z Fold 8 series is seen as an important testing ground for Samsung to evaluate the technology before introducing it to more mainstream flagship smartphones.

Such caution is understandable. Samsung remains particularly sensitive to battery-related safety concerns following the Galaxy Note 7 crisis, which caused significant damage to the company.

The encouraging news is that silicon-carbon technology is now rumored to be coming to the Galaxy S27 Ultra, potentially bringing a more substantial capacity increase.

According to recently leaked certification documents, the Galaxy S27 Ultra could feature a 5,700mAh battery, an increase of 700mAh, or 14%, compared with its predecessor.

The leaked certification information also suggests that the Galaxy S27 Ultra could support wired fast charging at up to 65W.

That remains below the 100W threshold already surpassed by numerous smartphone brands, particularly Chinese manufacturers. Still, 65W would be a reasonable charging speed for a Samsung flagship.

Could the Galaxy S27 Ultra deliver two-day battery life?

What difference would a 5,700mAh battery make in everyday use?

Some Galaxy S26 Ultra and even Galaxy S25 Ultra owners report getting two full days of use from a single charge. In practice, however, stretching a 5,000mAh battery across two days remains challenging, especially for people who frequently play games, stream videos or run multiple applications.

The additional 700mAh rumored for the Galaxy S27 Ultra could make a meaningful difference.

Instead of carefully managing power consumption and limiting usage to reach the two-day mark, users could potentially enjoy more consistent two-day battery life without making as many compromises.

Of course, actual battery endurance depends on several factors, including usage habits, screen brightness, network connectivity and software optimization. Battery capacity alone cannot guarantee the same results for everyone.

Even so, Samsung's potential transition to silicon-carbon batteries would mark a significant milestone.

After seven generations with virtually unchanged battery capacity, the Galaxy S27 Ultra may finally deliver one of the most practical upgrades the Galaxy S Ultra lineup has needed for years.

Hai Phong