Samsung Galaxy Watch 9 · Reported Feature

The 40mm battery grows to 400mAh; the 44mm holds at 435mAh

What we’re expecting

SamMobile published Galaxy Watch 9 battery part numbers in March 2026. The 44mm cell is rated 435mAh under part number EB-BL355BAY, which maps to the Watch 9's own SM-L355 model code, not a Watch 8 part. That matches the Watch 8 44mm at 435mAh, so the larger size holds steady. The 40mm grows to a rated 382mAh, marketed near 400mAh, up from the Watch 8 40mm's 325mAh. Endurance still hinges on the chip.

Samsung's reportedly bumping the 40mm Galaxy Watch 9's battery from whatever it shipped before up to 382mAh, close to 400mAh but not quite there. The 44mm stays at 435mAh. A bigger battery in the smaller size is welcome, but 382mAh is still a modest number, and smaller watches already run harder to power the same features in less space.

iDevice Confidence

Widely reported

Widely reported by reliable sources, short of an official word.

How does Samsung Galaxy Watch 9's battery life compare?

Standalone runtime per charge, longer is better.

Galaxy Watch Ultra 2
~72hrs est. (~800mAh leaked)
Samsung Galaxy Watch 9
~50hrs est (40mm) / +30% vs Watch 8
Galaxy Watch Ultra (current)
Up to 48 hours (590mAh)
Apple Watch Ultra 3
Up to 42 hours
Samsung Galaxy Watch 8
Up to 40 hours (40mm)
Apple Watch Series 12
Improved (est. 24–36 hrs)
Pixel Watch 4
~30hrs (41mm) / ~40hrs (45mm)
Apple Watch Series 11
Up to 24 hours

Tethered and USB-C-powered devices excluded (no standalone rating).

Sources reporting this (1)

Galaxy Watch Ultra 2 reportedly gets a massive battery upgrade, twice the size of a normal Wear OS watch9to5Google · Jun 10, 2026