https://www.cnet.com/news/galaxy-s9-battery-size-rumor-leak/

If you're hoping that the Galaxy S9 will last twice as long as your Galaxy S8, you may want to lower your expectations. The batteries for the Galaxy S9 and Galaxy S9 Plus are rumored to stay the same size as their predecessors, according to the latest leak.

If you head over to online phone component retailer Union Repair, you'll find a listing for battery replacements for the Galaxy S9 and Galaxy S9 Plus. That's 3,000mAh for the S9, which is the same capacity as the Galaxy S8 and the Galaxy S7 before it.