Internal Samsung SDI documents marked “Strictly Confidential” have leaked, and whoever authorised that distribution list is probably having a rough morning.
The files show Samsung testing smartphone batteries of 12,000 mAh and 18,000 mAh — while the Galaxy S26 Ultra, which went on sale recently, ships with 5,000 mAh.
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
Big numbers, messier reality
Two development branches show up in the documents. One targets 12,000 mAh, the other 18,000 mAh — nearly four times what the S26 Ultra ships with. Both run on silicon-carbon battery tech, which is what’s been allowing Chinese manufacturers to dramatically increase capacity without turning their phones into bricks.
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On paper, either
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