The Galaxy S21 battery life tests bring unwelcome surprise

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The Galaxy S21 battery life tests bring unwelcome surprise
Samsung's fresh Galaxy S21 series is powered by the newest Snapdragon 888 in the US which may not beat Apple's A14 in raw benchmarks, but has the exciting advantage to ship with a fully integrated 5G modem, as opposed to Apple's tack-on modular solution that is a battery hog. 

Consequently, Qualcomm boasts up to three times performance per watt improvement when compared to the Snapdragon 865 in the S20 and ditto for Samsung's other S21 chipset, the Exynos 2100. Add to these the lower resolution that the Galaxy S21 uses, and the adaptive refresh rate screen technology, and it's party time.

Samsung Galaxy S21 battery life test

'Power to last through your day,' says Samsung, and then some

  • 4000mAh
  • 25W-45W wired charging
  • 15W wireless charging

Curiously enough, the S21 is the only one of the new trio for which Samsung mentioned more than a day of battery life, even though it has the smallest battery pack. Last year, the Galaxy S20 got an excellent score with its screen at 60Hz, as battery life reached 12 hours and 12 minutes during our testing procedure, but when you switched to 120Hz, the battery life took more than a 30% hit down to 7 hours and 45 minutes. 

Since the S21 has a more up-to-date display technology with adaptive refresh rate, and lower screen resolution, it should clock in at least those hours, despite the more powerful chipset, right? Not really, as you can see from the results below. Bear in mind that these are shown at 60Hz, while at 120Hz adaptive refresh the S20 matches its heir.


hours Higher is better
Samsung Galaxy S20
12h 12 min
Samsung Galaxy S21
9h 6 min
Samsung Galaxy S21 Ultra
16h 7 min
Samsung Galaxy Note 20 Ultra
11h 57 min
Samsung Galaxy S20 Ultra 5G
12h 23 min
Apple iPhone 12 Pro Max
14h 6 min
Samsung Galaxy S20 FE
12h 28 min
OnePlus 8
12h 15 min

The battery unit of the S21, whose model number is EB-BG991ABY, sound familiar? It is actually the 4000mAh EB-BG980ABY piece that is found inside the S20 as well, so battery life should be about the same, right? We thought not, for the reasons below, but the actual testing proved that the S21 battery life isn't better than what the S20 offers, and is actually worse in some cases. 




Galaxy S21 vs Galaxy S20 battery life efficiency


The FHD (S21) vs QHD (S20) display


While the Galaxy S20 is equipped with an overkill 1440p resolution on a comparatively tall and narrow 6.2" screen, Samsung went the smarter route this time around, and is launching the S21 with a 1080p panel. The lower pixel density makes for a much more frugal panel, as there are 1MM+ less pixels to light up and manage with the graphics subsystem. Our own battery tests show that phones with FHD screens perform 20-30% better in terms of battery life than those with QHD or higher screen resolutions when we average out for the battery capacity difference.

Tap the lower band of that range, and the S21 should outlast the S20 with two hours, hitting a tenner in our browsing and scrolling battery test, all other things being equal. The point is they won't be equal, however.

The 5nm (S21) vs 7nm (S20) processor


Compared to the second-gen 7nm (7LPP) Snapdragon 865 processor in the S20, made in the TSMC foundry, the 5nm Snapdragon 888 is made using Samsung's new EUV process. The fact that Qualcomm not only switched nodes from 7nm to 5nm, but also the foundry itself , is a vote of confidence in Samsung's Extreme UltraViolet (EUV) lithography.

According to Samsung, its 5nm EUV process offers not only a fifth smaller footprint of the chipset at the same performance, but also about 20% smaller power draw. Alternatively, phone makers can choose to gain a 10% performance increase at the same battery consumption. Given that mobile chipsets are already powerful enough for anything you may throw at them, and the new X1 cores are clocked at the same 2.84GHz as the 865, Samsung is likely to go with the generous power consumption decrease.

The integrated (S21) vs standalone (S20) 5G connectivity


The 7nm vs 5nm process alone won't make a significant extra difference in battery life between the two phones, though, as the main power draw comes from the display. The phones' 5G connectivity battery draw, however, will, as maintaining a link to the 5G network is a battery hog. Why? Well, first off, before Snapdragon 888, only Huawei had integrated 5G system-on-a-chip (SoC) for flagship phones. Qualcomm made do with chipsets like the 765 in the Pixel 5 or LG Velvet, which, albeit having the 5G modem as an integral part of the chipset, are a far cry from its 8-series in terms of performance.

With Snapdragon 888, however, Qualcomm managed to finally do what it does best - pair the fastest ARM Cortex cores available with a new powerful Adreno 650 graphics AND fuse them with the X60 5G modem that is also made on the 5nm process. That alone amounts for a significant drop in power consumption when connected to a cell tower but Korean media just reported that there will also be improvements in the 5G antenna hardware.

Next-gen 5G antenna isolation


Fast 5G networks like Verizon's Ultrawide Band (UWB) mmWave can carry a lot of data at once and fast, but have very bad signal penetration that forces phone makers to slap a bunch of extra antennas all around their handsets just so that the signal can pass through your grip alone.

Samsung, however, is using the next generation of low permittivity polyimide (PI) films for the 5G antennas in the Galaxy S21 phones. This means easier signal passthrough, and less toll on the battery. 

Taken individually, all these power draw improvements, with the exception of the lower pixel density, may not amount to much, but as a whole could've provided a theoretical boost to the Galaxy S21 battery life from the same 4000mAh battery capacity. They could've, but they don't so you should expect both phones to last you about a day, and that's that.

Related phones

Galaxy S21
  • Display 6.2 inches 2400 x 1080 pixels
  • Camera 12 MP (Triple camera) 10 MP front
  • Hardware Qualcomm Snapdragon 888 8GB RAM
  • Storage 128GB, not expandable
  • Battery 4000 mAh
  • OS Android 11 Samsung One UI

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