Sunday, November 5, 2017

Google Pixel 2 XL Charging Speed is Functionally Capped at 10.5W

For a long time, it seemed to consumers that as battery capacity increased in smartphones, charge time would naturally increase as well. To solve the problem, many companies worked on various methods of quicker charging. Over the years, we have seen the rise of various standards such as USB Power Delivery, Qualcomm Quick Charge, Samsung’s Adaptive Fast Charge, Huawei’s SuperCharge and OnePlus’s Dash Charging just to name a few.

However, charging implementations differ in different smartphones. The fact that phone A and phone B use Qualcomm Quick Charge 3.0 does not mean that their charging speed is equivalent. In fact, charging time on a phone depends on many factors apart from the use of a charging standard.

We compared different charging standards, and found that Dash Charging on OnePlus phones as well as SuperCharge in Huawei phones performed the best when it came to charging speed, thermal performance and efficiency. In our comparison, we noted that the Pixel XL charged slowly and charging speed was not competitive against other devices, despite being rated for up 18W. This was not because of any fault in USB-PD, but because of the fact that the voltage had been capped.

Now, in a new report by Nathan K., it has been discovered that the new Pixel 2 XL also carries similar limitations. Strictly speaking, this is not an “issue”, but it is definitely disingenuous marketing, adding onto the list of issues with the device.

Pixel 2 XL Charging

Nathan K. performed a charging test on the Pixel 2 XL and shared his results on Google+. His report mentions that the Google Pixel 2 XL charges slower than expected. Users had already been commenting that they felt their Pixel 2 XL units had not been charging as fast as they should have been, and their experiences have now been corroborated.

The Pixel 2 XL comes with a wall adapter which has the advertised capacity to charge the phone with up to 18W of current. But in the wattage-temperature graph, there is no instance in charging time where the charger draws 18W of current. The wattage starts at about 15W in the beginning, but switches down to slightly above 10W within minutes. The Pixel 2 XL continues to charge at this rate until about 50 minutes into the cycle, where it begins to gradually slow down until the end of the cycle with a full charge (from 15% battery) taking 2.5 hours. Maximum temperature recorded was 32.6° Celsius.

Nathan K. noted that the first-generation Google Pixel used multi-stage Li-Ion rapid charging: three stages of constant-current, followed by a final constant-voltage stage. However, the Pixel 2 XL uses a single stage of constant-current, followed by constant-voltage.

He suggests that the reason for the slow charging speed on the Pixel 2 XL is that Google and LG are trying to avoid putting strain on the battery in order to maximize its longevity. Instead of opting for performance, the manufacturers have been “extremely conservative with the charging current and temperature”. This could be done to save the battery from battery degradation issues like the ones which were faced by the Nexus 6P.

Finally, he noted that the 5″ Google Pixel also charged at a maximum 15W as against the advertised 18W. The smaller battery (2770mAh) of the Google Pixel “justified this difference in wattage.” With the Pixel 2 XL, the difference is much bigger.

For now, it is unknown what Google has to say as a response to this new development.

Source: Google+: Nathan K.

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