The combination of Snapdragon 865 and a 5G external modem was always going to hurt battery life, even with a 5,000 mAh battery. Perhaps unsurprisingly then, the Samsung Galaxy S20 Ultra falls short of its peers like the Apple iPhone 11 Pro, the Samsung Galaxy Note 10 Plus and even the Galaxy S10 Plus. Now, Tom's Guide has demonstrated just how poorly the S20 Ultra fares, especially with its display running at 120 Hz.
https://www.notebookcheck.net/Galaxy-S20-Ultra-Samsung-s-flagship-has-comparatively-disappointing-battery-runtimes-despite-its-5-000-mAh-battery.454782.0.html