Why this answer matters
The adapter can safely have a higher maximum rating when standards and negotiation are compatible, but the phone controls the power it accepts. Maximum charger wattage and device charging capability are not the same thing.
3 requirements3 verification steps1 primary source
Requirements
What has to be true
- A compatible USB-C power adapter and cable.
- Samsung's S25-series documentation uses a 25W adapter and 3A USB-C cable for the base S25 fast-charge test condition.
- Use a standards-compliant charger; charging speed can vary with temperature, battery state and use.
Verify it yourself
Use this test sequence
Change one variable at a time so you know which requirement made the difference.
- 1
Confirm whether the phone is S25, S25+ or S25 Ultra.
- 2
Check the charger's supported USB-C output modes, not only the large marketing wattage printed on the front.
- 3
Try a known-good cable if charging repeatedly drops or stays unusually slow.
Limits
What this answer does not prove
- A 45W charger may still charge the S25, but the base S25 does not become a 45W device because the adapter can supply more.
- Real charge time varies from Samsung's controlled test conditions.
Relevant DeviceOK checks
Test the part you can observe
Charger Wattage MatchCompare a device's entered power requirement with a charger's rated wattage while keeping USB-PD/PPS and voltage-profile limits explicit.
→USB-C Cable Power Rating CheckCompare an entered cable wattage rating with the power you want to carry, while keeping protocol/e-marker limits explicit.
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