2025 was a year of impressively large smartphone batteries. We saw 7,000mAh and 8,000mAh batteries become mainstream, and Honor even crossed the previously unthinkable 10,000mAh threshold. Almost all of these advances came from Chinese phone companies switching to silicon-carbon battery technology. Samsung and Apple were notably slow to adopt this shift. But Samsung appears unwilling to stay on the sidelines of the big-battery race much longer. According to a tipster, Samsung's SDI division is testing a massive 20,000mAh dual-cell battery for smartphones — and notably, it uses silicon-carbon technology. The design reportedly uses two cells of different sizes. One cell is 6.3mm thick with 12,000mAh capacity, and the second adds 8,000mAh at 4mm thick. Combined, they reach the eye-catching 20,000mAh total. What's particularly remarkable is that even the single 12,000mAh cell already surpasses the 10,000mAh batteries found in Honor's Win series. In other words, Samsung may be testing batteries that go well beyond what is currently considered "extremely large." According to the tipster, the full 20,000mAh system could provide up to 27 hours of screen-on time and withstand around 960 charge cycles per year (on paper). However, the batteries are reportedly experiencing swelling issues during testing, and long-term stability remains unresolved. A second source noted that the 8,000mAh cell expanded from 4mm to 7.2mm after testing — a concerning sign for smartphone use. As usual, this information should be taken with a grain of salt. Ref: Gizmochina