Internal Samsung SDI documents marked “Strictly Confidential” have been leaked, and whoever authorized this distribution list is probably having a rough morning.
According to the files, Samsung is testing smartphone batteries with 12,000 mAh and 18,000 mAh – while the Galaxy S26 Ultra, which went on sale recently, ships with 5,000 mAh.
Big numbers, messier reality
Two branches of development appear in the documents. One targets 12,000mAh, the other 18,000mAh – almost four times what the S26 Ultra ships with. Both are powered by silicon-carbon battery technology, allowing Chinese manufacturers to dramatically increase capacity without turning their phones into building blocks.
On paper, both numbers would make Samsung the absolute leader in battery capacity overnight.
Neither is running smoothly. The 12,000 mAh version is already too thick in several prototypes, although swelling is being monitored. In the 18,000 mAh version, a cell is running hot and the charging management software is not yet ready.
And hanging over both is the unpleasant fact that Samsung’s previous 20,000 mAh prototype gave up after 960 charge cycles – well below the 1,500 cycle target. A phone that deteriorates significantly before its third year is a hard sell at any price.
Late to a party Samsung once threw
No product has been announced. There is no timeline. At the moment these are laboratory experiments, and quite problematic ones at that.
The irony is that Samsung has made large batteries before. The Galaxy M51 launched in India in 2020 for around $300 and featured a 7,000mAh cell that actually lasted two days. Then the company simply stopped caring. The years passed, the flagships continued to ship with the same number, and no one at Samsung seemed to care much.
Over in the US, OnePlus launched the 15R with a 7,400mAh battery for $699 – and that’s the largest you’ll find in any mainstream phone in the US right now. India and China moved even faster; Mobile phones there have exceeded the 10,000 mAh mark, while Samsung was apparently busy elsewhere.
