Certification for a 1.17Wh battery with a capacity of 303.8mAh was issued on June 23 by the KTR, a Korean regulatory body that approves and tests new hardware ahead of public sale.
The battery seems to be destined for a future Apple Watch, given the shape, capacity, and model number of A2327. The current Apple Watch Series 5 has a 296mAh battery, a similar model number of A2181, and is visually identical. The battery is also listed in the filing as for “fitness,” which would be an appropriate categorization for Apple Watch.
A larger 303.8mAh in a new Apple Watch would offer a larger capacity than in previous generations. This could be facilitated by the removal of the Force Touch technology layer, which was made defunct in WatchOS 7. Without this component in future Apple Watches, internal space could be made available for a slightly larger battery.
Apple claims that Apple Watch Series 5 offers an 18 hour battery life, but since this new battery is only slightly larger, it would be unlikely for the Series 6 battery life to be considerably better. Any significant battery life improvements would be more likely to come from improved power efficiency rather than a larger battery.
Earlier this week, it was rumored that Apple Watch Series 6 could feature blood oxygen monitoring, which could consume more power and account for the need for a larger battery.
Apple Watch Series 6 models are expected for a fall launch, and are rumored to feature faster performance, better water resistance, and improved wireless transmission for faster Wi-Fi and cellular speeds.