If an S25 Ultra started losing charge fast in late July 2026, read this first. Owners on Samsung's forums reported losing five to seven percent an hour on standby after the July update, one measuring 143 percent of a full charge used in a day against 80 percent before it, and the reports point to a background job stuck in a loop, with WhatsApp's encrypted backup named in some cases. Samsung had not confirmed a cause. Open Settings, Battery, and if one app leads by a wide margin, stop it and let any backup finish on Wi-Fi before you touch anything else.
Differential
Likely causes of “Samsung Galaxy S25 family battery drains too quickly”, and how to tell them apart
- 1
A stuck background task after the July 2026 update
What separates it Steady loss while the phone sits idle, at a rate of five to seven percent an hour
How to confirm The reports describe processes looping and keeping the main processor awake; Settings, Battery shows the app holding it
- 2
WhatsApp's encrypted backup
What separates it WhatsApp is at or near the top of the battery list although you barely used it
How to confirm Reports named the backup loop; let it finish on Wi-Fi and the charger, or pause the automatic backup
- 3
A battery a year and a half old
What separates it The phone charges to 100 percent and then falls quicker than it did last winter
How to confirm Samsung Members diagnostics reports the cell's condition; GSMArena's 14:49 active use score is the new-phone benchmark
- 4
5G or weak signal
What separates it Drain is worst in a building with one bar
How to confirm The phone raises radio power in weak signal; compare a day on Wi-Fi
Before you touch a setting
Record this first — changing settings destroys the evidence
- The date the drain began and whether it follows the July 2026 update
- The top three apps in Settings, Battery and their percentages
- Whether it loses charge overnight on Wi-Fi
- How many hours of screen-on time a day you get now
Try in this order
0 of 5 completedRead the battery list
ReversibleOpen Settings, Battery and look at the top three. A gap of several times between first and second is the stuck process.
Let a backup finish
ReversibleIf WhatsApp leads, leave the phone on Wi-Fi and the charger overnight so the backup can complete, or turn off the automatic backup.
Restart and install updates
ReversibleRestart, then open Settings, Software update. The reports expected a later patch to settle it.
Test overnight on Wi-Fi
ReversibleCharge to 100, put the phone on Wi-Fi, leave it untouched for eight hours and note the percentage lost.
Run the battery diagnostic
ReversibleOpen Samsung Members, Support, Phone diagnostics, Battery.
Model-specific
What is true of this model and not of its siblings
- Other models this page answers
- These steps also fit the Galaxy S25+.
Stop boundary
When this stops being a self-service repair
- !If it loses more than a quarter overnight on Wi-Fi after the top app is stopped and a restart, run Samsung Members diagnostics and contact Samsung support with the battery screen
- !If the back bulges or the phone is hot while idle, stop using it and visit a service center the same day
Evidence ledger
Sources behind this answer
Reports of drain and heat on S24 and S25 Ultras after the July 2026 update, and the suspected WhatsApp backup cause, published 2026-07-30.
Standby loss of five to seven percent an hour and the 143 percent against 80 percent example.
Active use score of 14:49 h and the 5000 mAh battery.
Exact questions
Common questions
Did the July 2026 update drain S25 Ultra batteries?+
9to5Google and other outlets reported S24 and S25 Ultra owners seeing heavy drain after the update, with a stuck background job suspected; Samsung had not confirmed it.
How much standby loss is too much?+
The complaints described five to seven percent an hour, which would empty the phone in about a day of doing nothing.
How long should an S25 Ultra last?+
GSMArena measured an active use score of 14 hours 49 minutes when new.
How do I tell a worn battery from the July 2026 drain?+
A worn battery falls quickly under load but holds its charge overnight on Wi-Fi. The July 2026 reports describe the opposite: a phone that loses five to seven percent an hour while idle, with one app leading Settings, Battery. Samsung Members diagnostics reports the cell's condition either way.