Samsung S9+ Battery

The Galaxy S9+ uses a 3,500 mAh non-removable battery, supports both wired and wireless fast charging, and is capable of full-day usage under typical conditions (with manufacturer-listed video, talk, and playback times). In real-world use, performance may vary and some users report shorter screen-on times depending on usage and software version.

Capacity: 3,500 mAh for the S9+ model. 
Battery type: Non-removable lithium-ion (Li-Ion) / Li-Polymer battery. 
Charging:
Wired fast charging supported (via USB-C) — compatible with Quick Charge 2.0. 

Wireless charging supported (Qi and PMA standards) for regions where supported. 


Usage estimates (Samsung official for S9+):

MP3 playback (Always On Display on): up to ~58 hours. 
MP3 playback (AOD off): up to ~102 hours. 
Video playback: up to ~20 hours. 
Talk time: up to ~35 hours. 
Internet use (WiFi): up to ~15 hours.