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Monday, July 1, 2019

Wired and Qi Charge Rates for a Pixel 3

Since I've been writing about wireless charging, I thought I should do some quick tests especially after being challenged by Qi advocates that I'm being harsh on the technology. A couple of years back I tested with a phone and was getting around 2 to 3 W rate, and wasn't impressed, but it has apparently improved since then (or my data point was skewed). I took my Pixel 3 which has wireless Qi Charging, and tested with two wired and two wireless options. The phone is about 2 months old, so hard to get a better test case, and the battery is around 10 Wh in capacity. For the wired tests I used the USB C cable and adapter that came with the phone (18 Watt), then an Anker 60 W PowerPort Atom PD 2 with a USB C cable rated for up to 100 W(about $60 worth of charging gear). For the wireless Qi I used the Google Wireless Charger for Pixel ($80) and an LK Qi Fast Wireless Charging Pad ($16). (Annoyingly the LK cable in the box only goes to a USB A, you need a USB adapter to actually plug into).

Google Wireless Charger (Left) and LK Fast Wireless Charger (Right)

Now this was not a scientific experiment where I placed the phone on the chargers with sub-mm precision, made sure the environment was identical each time, or run multiple tests to check for outliers, so there's going to be some error here. I also didn't use any high end equipment to measure the performance, just the % battery as reported by the phone itself, and the clock, so especially early on there will be some integer related errors - however this is more as an example of what a user will actually experience, and in the end the results were pretty definitive.



The Pixel charges faster to about 50%, then starts to slow down. The out-of-the-box wired approach gets to 50% in under half an hour, and a full charge in about 1h15min, while the more expensive wired charger takes around 35 minutes to get to 50% but then 1h46min to get to 100%, with about 25 minutes of that being the last 10%, not sure why it slowed down so much (I did look at the battery temperature, it didn't report as high). Assuming 10Wh in the battery, that means an 11W rate for the first 50% of the charge and 8W overall with the default charger, and around 8.6W/5.7W for the Anker charger. It looks like, with this one data point, that there's no point in spending the money or using anything other than the default wire charger for a Pixel 3.

For the wireless Qi approach the official Google Wireless Charger for Pixel takes about an hour to get to 50% charge, and 2h30min to fully charge, giving a 50% charge rate of ~5W and overall at 4W. I did not see the 10W fast charging claimed for a Pixel 3 - my results are a bit slower than I saw in this article, which got 22% charge in 15 minutes (an effective 8.8W rate). I have a plastic case on my phone, I tried with and without the case and it really made no difference to the rate. For the LK Charger, it's 1h40min to 50%, and nearly 4 hours to 100%, for 3W charging to 50% and 2.6W to 100%. It was painfully slow, and I had to do the test a couple of times as I fell asleep while waiting and woke up the next day at 100% charge.

Unsurprisingly, wired wins, and by a lot. Up to 11W is pretty good when only a few years ago wired USB was at around 2.5W, and getting to 50% in under thirty minutes is really handy if you need to top up quickly. The charge rate with the official Pixel charger was about half, so 5W for the first 50%, but I have to say it felt adequate, and I wasn't really frustrated by the speed of charging. The LK on the other hand charged at 3W and was really frustratingly slow, and near 4 hours for a full charge. For me it seems there's a break point between 3 and 5 Watts that makes a huge difference if I'm awake, if I go to sleep it just charges overnight and it really makes no difference if it took 2 or 4 hours.

While it was adequate to charge at 5 Watts with Qi, I still found I prefer wired, as for the most part I really wasn't running out of charge during the day. Now that I was paying attention, I was finding that I'd leave home at around 8.30am at 100%, and still be at 20% charge at midnight, with some days even getting to late morning the next day before running down to 0%. I don't use GPS much, so that may help, but that's a lot of use time in a phone, so a quick wired charge in the evening while I have dinner is usually more than enough. It was kinda handy to drop the phone onto the stand, but it wasn't so good that I stuck with it consistently.

The Google charger comes with a few extra features such as auto-do-not-disturb, slowly brightening lights before an alarm goes off, and photo display. I didn't particularly like these things, and found them of no value. My wife, however, did. She tried out the Google Wireless Charger for her Pixel 3 and I was quickly told I wasn't getting it back, and now it's what she uses exclusively. I got left with the LK, which sits on my nightstand and I sometimes use it if I'm going to sleep to charge overnight, but otherwise it sits idle.

So, for me I'd say the Google Wireless Charger does a reasonable job, but not so good that I personally find it worth the $80. If it did 10W the marketing claims (or someone can tell me why I'm limited to 5W actual during the first 50%), then that would be different and I might be more easily persuaded. It's clear I'm not the target market though, and it was a big win with my wife - if you're not looking for the absolute fastest charging and like the additional features, the Google Wireless Charger seems a good buy. At $16, for occasional use the LK charger is adequate, but I wouldn't miss it if it were gone.

So Qi wireless charging has come along in the last few years, and for the right person, is a good choice and for the Pixel 3 go with the official Google Wireless Charger, especially if you think you'll like the features that it comes with.