Samsung SDI has been testing 12,000mAh, 18,000mAh and 20,000mAh Silicon-Carbon batteries – internal test reports have leaked on X and they show that the company still has work to do.
There is no info on the 20,000mAh battery, but the reports for the other two note that it failed after 960 charge cycles. That clearly won’t do. The two smaller batteries aim for 1,500 cycles, but whether they can get there is still under test.
The 12,000mAh battery, SDI-DC12K-SiC-V2, is a dual cell design consisting of one 6,800mAh 4.7mm cell and one 5,200mAh 3.2mm cell. The stack thickness should be under 9.3mm (though 2 out of 7 test samples ended up being thicker).
The 18,000mAh battery, SDI-TC18K-SiC, is a triple cell design: 6,699mAh 4.2mm, then 6,000mAh 3.9mm and 5,257mAh 3.28mm. The goal for the stack is around 12.3mm, but thermal interface layers between the cells pushed the test samples to 12.8mm.
Test reports for the 12,000mAh and 18,000mAh Si-C batteries from Samsung SDI
According to the test notes, Samsung SDI is looking to redesign the layers between the cells and how they are stacked. It is also working on the battery management firmware.
The 12,000mAh battery is predicted to achieve 20-25 hours of screen on time in a phone connected over 4G and Wi-Fi. It is optimized for stability. Meanwhile, the 18,000mAh battery is focused on high capacity and endurance.
Of course, we’d love to see some of these Si-C cells on their own – a 6,800mAh 4.7mm cell or, more likely, the 6,699mAh 4.2mm cell would be just right for a flagship. Very early rumors claimed that the Galaxy S26 Ultra would use a Si-C battery, but that clearly didn’t pan out. Maybe Samsung SDI will complete the testing in time for the S27 Ultra. Naturally, foldables would also benefit from thin, high-capacity batteries.