Samsung's Galaxy S9+ has the same battery capacity as the Galaxy S8+— 3,500 mAh — so we didn't expect a sizable boost in endurance. And we didn't get one, either, even though the Snapdragon 845 chip inside Samsung's new flagship is supposed to be more power-efficient.
We put the Galaxy S9+ through the Tom's Guide Battery Test, which involves surfing the web over 4G LTE (in this case, on T-Mobile's network). We set each phone screen we test to 150 nits of brightness and turned off Auto-Sync (for notifications) and GPS. In this particular case, calibrating the screen to 150 nits meant setting the brightness of the S9+'s screen to 50 percent.
Galaxy S9+ Battery Life vs. the Competition
The Galaxy S9+ turned in a runtime of 10 hours and 59 minutes, which is comparable to the 11:04 that the Galaxy S8+ turned in last year. The iPhone X was slightly behind, at 10:49. The Galaxy S9+'s runtime is comfortably ahead of the smartphone category average of 9 hours and 50 minutes.
The absolute longest-lasting phones we've tested, such as the Asus ZenFone 3 Zoom and the ZenFone 4 Max, can keep going for up to 15 or 16 hours. And the underrated Huawei Mate 10 Pro beats the Galaxy S9 and all other premium flagships with its great runtime of 14:33.
In everyday use, the S9+ stood up well. One day after I streamed music for over an hour on my morning commute, taking several photos and shooting a slow-mo video, the S9+ had 60-percent charge left by 12:49 p.m. I had unplugged the phone at 6:50 a.m.
After lunch, I used the S9+ a ton, shooting our review video for it and making additional comparisons with other phones. Then, I uploaded a bunch of photos and videos to Dropbox. By 8:12 p.m., I was down to 6 percent, so you should expect even better battery life with light to moderate usage.
It's also worth noting that the S9+ supports Samsung's quick charging. And unlike with the iPhone X, the quick charger comes in the box. After 15 minutes, the S9+ was already at 19 percent, and it reached 38-percent capacity after 30 minutes. At 60 minutes, the S9+ got to 75 percent.
Credit: Tom's Guide
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Mark Spoonauer is the global editor in chief of Tom's Guide and has covered technology for over 20 years. In addition to overseeing the direction of Tom's Guide, Mark specializes in covering all things mobile, having reviewed dozens of smartphones and other gadgets. He has spoken at key industry events and appears regularly on TV to discuss the latest trends, including Cheddar, Fox Business and other outlets. Mark was previously editor in chief of Laptop Mag, and his work has appeared in Wired, Popular Science and Inc. Follow him on Twitter at @mspoonauer.