Samsung is reportedly testing batteries with gigantic capacity. Up to 18,000 mAh is in play

While Chinese manufacturers commonly equip their flagships with silicon-carbon batteries exceeding 7,000 mAh, the newly launched Samsung Galaxy S26 Ultra still sticks with the classic 5,000 mAh. However, leaked internal documents show that the South Korean giant is certainly not idle – Samsung SDI laboratories are testing prototypes with capacities that will take the competition’s breath away.

20,000 mAh? Not yet

According to documents published on network X by leaker @phonefuturist, Samsung SDI is working on three versions of silicon-carbon batteries. However, the most ambitious prototype with a capacity of 20,000 mAh had to be postponed – it failed after only 960 charging cycles, which is insufficient for regular use.

Samsung SDI is testing 12K, 18K mAh Si/C cells. The 20K failed at 960 cycles. Race is on. 👀

Full PDF available, Samsung tracking system didn't work much. Anyways it's not free. pic.twitter.com/D8NDy4weNw

— Schrödinger (@phonefuturist) March 9, 2026

Two promising candidates

Attention is therefore shifting to the 12,000mAh and 18,000mAh variants. The smaller one, designated SDI-DC12K-SiC-V2, uses two cells – 6,800mAh (4.7 mm) and 5,200mAh (3.2 mm). The total thickness should remain below 9.3 mm, which would theoretically make it usable even in regular smartphones.

The larger 18,000mAh battery, designated SDI-TC18K-SiC, then combines three cells with capacities of 6,699 mAh, 6,000 mAh, and 5,257 mAh. With a total thickness of around 12.8 mm, it would be more suitable for rugged phones or devices with a larger build.

Battery life from another world

Test protocols suggest that the 12,000mAh battery should provide 20 to 25 hours of active screen usage when connected via 4G and Wi-Fi. Samsung SDI aims for a lifespan of 1,500 charging cycles before capacity drops to 80%, which would correspond to approximately four years of intensive use.

Samsung is reportedly testing batteries with gigantic capacity. Up to 18,000 mAh is in play Adam Kurfürst News Adam Kurfürst News

However, developers are still addressing issues with the thermal interface between cells and optimizing firmware for battery management. When these technologies might enter mass production is not yet clear – however, it is speculated that Samsung could deploy silicon-carbon batteries no earlier than with the Galaxy S27 series.

Do you think Samsung will catch up with Chinese competition in the battery sector?

Sources: @phonefuturist/X, GSMArena, Notebookcheck, SammyFans