After the update to S9 on 16 June 2021, battery life reduced substantially. Samsung agent explained battery probably at end of normal life [about 2 years+] and so was replaced at cost of $110. Little difference. Phone not in use from 2300 to about 800 but noted battery drained some 20% overnight whereas the Tab S [10.5"] only loses 5%. By end of day battery is at about 30% if not lower which is near old battery. There has been no change to apps. Doubt that battery is faulty. Only suspect Samsung update and power hungry changes. Could Samsung please explain why update resulted in substantial power usage.