15Apr 2016

I discussed in a prior post the charging of the 5.5-in Samsung Galaxy S7 Edge. In this post, we will look at its sister device, the 5.1-in Samsung Galaxy S7, specifically the US version (model G930) using the Qualcomm Snapdragon 820 chipset, also known as the 8996. The battery specifications on the S7 include a polymer cell rated at 3,000 mAh, equivalent to 11.55 Wh. The teardown on iFixit shows a cell that is manufactured by ATL  rated to 4.4 V. Once again, the choice of battery manufacturer is surprising given that Samsung Electronics for years sourced the vast majority of their batteries from their sister company Samsung SDI.

Samsung S7 battery

I charged the Galaxy S7 using the Samsung-supplied AC adapter and USB cable, with the device in airplane mode and the screen turned off. The charging data is next.

S7-charge curve

Let’s make a few observations. The measured battery capacity is 2,940 mAh at a termination current of 300 mA (C/10). This is consistent with Samsung’s claim of 3,000 mAh, usually measured in the laboratory at a termination current of C/20 or 150 mA.

The device reaches 50% after 31 minutes of charging, corresponding to a charge rate of 1C, i.e., a charging current into the battery of 3 A. The supplied AC adapter is rated at 5 V/2 A and 9 V/1.67 A and uses Samsung’s own version of Qualcomm’s Quick Charge technology for handshaking between the AC adapter and the smartphone. The device displays that charging is complete (the fuel gauge reads 100%) after 82 minutes, however it continues to draw a charging current for an additional 20 minutes at which point the device terminates the charging after 102 minutes.

Just like the S7 Edge, the battery maximum charging voltage is only 4.35 V, not the rated 4.4 V. This means that the actual battery maximum capacity is nearly 3,180 mAh but Samsung is making only 3,000 mAh available to the user. This further raises the likelihood that Samsung opted to lower the voltage (and sacrifice available charge capacity) in order to increase the battery’s longevity (cycle life) or decrease the battery swelling at the high charge rate of 1C, or perhaps both.

All in all, this appears to be a well-designed battery providing ample capacity to the user to last a full day with sufficiently fast charging. What is unknown is the battery’s longevity (i.e., how many days and cycles of use) and whether it was compromised in the process. Given that Samsung’s track record in providing battery longevity is not exemplary, that will remain a very important question and left to be answered in a future post.