Samsung has been under pressure for some time regarding battery capacity. The Galaxy S26 Ultra was launched earlier this year with a 5,000mAh cell. This is the same capability that shipped with the S20 Ultra in 2020. Meanwhile, Chinese brands like OnePlus and Xiaomi are fitting 7,000mAh and larger silicon carbon batteries into slim flagships. According to leaked documents, Samsung SDI is finally working to bridge that gap in a much bigger way.
according to A post on Schrodinger IntelHe posted what appears to be an internal Samsung SDI test document, which shows that the company is reportedly testing silicon carbon battery cells at 12,000mAh, 18,000mAh, and 20,000mAh capacities. Those are not typo errors. For context, the OnePlus Ace 6 Ultra just launched with an 8,600mAh battery, and that’s considered huge by current standards.
Samsung silicon carbon battery testing still faces hurdles
Leaked documents reveal that the 12,000mAh design uses two stacked cells: a 6,800mAh cell at 4.7mm and a 5,200mAh cell at 3.2mm. Total stack thickness is reportedly targeted at less than 9.3 mm. The 18,000mAh version reportedly uses three stacked cells and targets a 12.3mm stack, better suited for rugged or outdoor phones than slim flagships. So none of these are things you’d expect to see on the Galaxy S27 Ultra.
The big issue is sustainability. All three configurations reportedly failed in testing at around 960 charge cycles. Samsung’s internal commercial target is 1,500 cycles, so neither of these are even close to being ready for a cell phone. According to the Schrödingerintel blog, Samsung engineers are currently reworking the separator layers and stacking architecture. They’re also tuning the battery management firmware to extend longevity beyond that limit.
It doesn’t make any sense that a 12,000mAh Galaxy phone is coming soon. A more realistic scenario for the Galaxy S27 Ultra would be a single silicon carbon cell around 6,699mAh to 6,800mAh. It will fit into a typical flagship form factor and still boast a massive 5,000mAh over five years. Samsung’s own R&D leadership confirmed earlier this year that silicon carbon is under development, with the company “getting it ready.” The leak suggests that this is true, even if the finish line is still far away.
