Samsung reportedly tested Galaxy S27 Ultra prototypes with a 7,000mAh battery and no S Pen, but the larger pack is not expected to reach retail.
Leaker Kro says Samsung is instead targeting a 5,700mAh or 6,000mAh battery, likely using silicon-carbon anode technology already introduced in this year's Fold 8 devices.
That would still mark a step up from the 5,000mAh battery Samsung has kept in its Ultra flagships since the Galaxy S20 Ultra, even as it remains cautious on battery size and charging speeds.
Samsung's restraint follows the 2016 battery failure crisis, while rivals such as Oppo, Xiaomi and Vivo now ship phones with batteries up to 7,300mAh and charging speeds as high as 240W.
The Galaxy S27 Ultra is expected to launch in January, with the battery leak adding to reports of a broader design overhaul next year.