An inside source quoted by GalaxyClub revealed the model number and capacity of the battery that's going to be used for the future Galaxy S21 Ultra handset. In short - it's the same as the S20 Ultra. The model number of the battery is EB-BG998ABY and it's rated at 4,885 mAh so the typical capacity will surely be 5,000 mAh - matching the Galaxy S20 Ultra's juice pack. In contrast the Galaxy S21 and S21+ will get a bump in the battery capacity compared to their predecessors. Of course, the improved 5nm Exynos and Snapdragon chipsets will bring some efficiency improvements so we...
Source: https://www.gsmarena.com/samsung_galaxy_s21_ultra_will_retain_the_5000_mah_battery-news-45315.php