People love Wi-Fi and Cellular data, which are both wireless data connections. Those wireless methods are overwhelmingly preferred over cables. Most people don’t realize that their internet speed would be much faster if they used a cable, but that is because wireless internet is good enough. The wire-free benefits outweigh the negligible benefit of higher speed. Conversely, many are unhappy with wireless power. So, when it comes to wireless charging, apparently the experience is not yet good enough.
In a previous blog, I discussed four reasons why some people have such a poor experience with wireless charging that they give up altogether. There is a second equally large group of people that use wireless charging but are disappointed with the charging speed. There are solutions for this problem as well.
Ignoring the Numbers
Manufacturers routinely label wireless chargers designed to support Apple’s iPhones as 7.5 W capable and chargers designed for Galaxy phones as 10 W capable; and now 12 W capable with the Galaxy S10.
Samsung Charger 2.0 for 12W Charging with Galaxy S10
At the beginning of 2019, Xiaomi introduced a 20 W wireless charger that mates to their Mi9 phone. And just this week I read of another Xiaomi phone/charger pair rated at 30 W. Xiaomi proudly claims they have the highest wireless power charging capability in the world. In fact, this is the second top feature listed in their advertising. Clearly Xiaomi believes 20W is a big deal. I suppose for some disappointed users, that may be true.
Xiaomi 20W wireless charger for Mi9
If I go to Apple’s iPhone marketing pages, one has to look long and hard before finding any mention about wireless charging. And then it is labeled simply as Wireless Charging (works with Qi chargers). No mention about power capability. But then what company would list a feature with comparison specifications that imply to customers their product is inferior?
Marketeers know that consumers will believe 10 W is better than 7.5 W. I suspect that Xiaomi customers would reasonable expect their 20 W charger to charge 2.7 times faster than a 7.5 W capable iPhone.
As it turns out, I have found no correlation between a manufacturer’s claimed numbers and how those numbers relate to typical use cases, regardless which phone I studied. In fact, using a wireless charger the company has under development, I have shown that in some cases the performance advantage is reversed such that a lower power capable phone charges faster than a higher power capable phone!
For example, when compared against Xiaomi’s 20 W capable Mi9 phone using their $50 accessory charger, it takes only 10 minutes longer to charge a 7.5 W capable iPhone Xs to 80% using our prototype charger, while watching a movie. Eighty percent (80%) is important because that is a maximum recommended sustained charge to maintain long battery life. Apple’s recently released iOS 13 includes a feature that simplifies compliance with that objective.
Mi9 vs. Xs Charging while phones are active
A 10 minute deficit over the course of 90 minutes is not 2.7:1. It’s more like 1.1:1.
Reasonable people would say that the results I compared are not fair. Their argument would be that Xiaomi’s Mi9 has a 3300 milli-amp-hour (mAh) battery versus the Xs phone which has only a 2660 mAh battery.
Yes, a higher capacity battery takes longer to charge, but it should also provide an equivalently longer use time for the claimed mAh number to provide a meaningful benefit. Assuming this is the case for the Xiaomi Mi9, then the real benefit of 20W after factoring in the larger battery should be 1.4:1. But is a larger battery a fair benefit to award Xiaomi? I say not. Here is why.
Contrary to what consumers are told, a battery size in mAh means nothing for a consumer’s experience. Rather, it is the roundtrip usage time that is important. Roundtrip time means the time it takes to charge a phone plus the time one can use the phone until it must be charged again.
Said another way, if two phones are charged for 30 minutes, and they can be similarly used for 2 hours, does it matter that one phone’s display started with the number 50% while the other phone showed 40%? Of course not. Both phones provide the same user experience. Perhaps this is why Apple’s latest operating system also doesn’t show the battery percentage on the home screen.
Referring back to the Xiaomi and iPhone example, I tested how long each phone could record a movie until their batteries discharged from 100% to shut down. The Mi9 phone filmed for 219 minutes whereas the iPhone Xs recorded for 267 minutes; a 22% longer video recording time for the iPhone despite a 17% smaller battery.
For the test, both phones were set up filming the same scene, with screens 6” apart placed face down on a table. Both phones had a phone case: the iPhone Xs was encased in an OtterBox Defender and the Mi 9 was encased in an OtterBox Symmetry. [Note: Cases are important because over 85% of all phone users keep their phones in a case.]
Admittedly, the tests I described above did not use rigorous scientific methods. I only investigated one phone of each brand, and every element in a phone has a variable performance attribute which I didn’t consider. The operating power of the iPhone might have been 5% lower than normal. The power in the Xiaomi charger might have been 10% lower than normal. But even with those considerations, there should have been a significant observable difference for a phone with a 2.7:1 charging power advantage.
While I’ve only played with the Mi9 for a while, and considering the $425 price, the Mi9 is a fine phone. Comparing a $425 Xiaomi phone to a $1,000 iPhone is like comparing a Toyota to a Mercedes Benz. But I chose the Xiaomi Mi9-iPhone Xs pair because this blog is about wireless charging experience, and Xiaomi claims to have the most powerful wireless charging phone in the world while the iPhone has claimed the lowest. It would be reticent to ignore evaluating the most extreme cases of wireless charging.
With regards to the other phones studied ( two Galaxy S9s, one Galaxy S10), the results were the same. No correlation between claimed charger power and charging time.
The larger batteries of the Galaxy phones also provided no advantage. Whereas the iPhone video recording time from 100% to 0% was 267 minutes, the S10 recorded for 250 minutes. Ignoring the small difference in recording times, the S10 battery is 3400 mAh versus the iPhone Xs battery of 2660 mAh. A 28% larger battery should have brought some advantage, but it didn't.
The takeaway from my research is that one should ignore wireless charging power numbers listed on a box or in marketing literature. In my opinion, it means essentially nothing.
So, what gives? One word: Heat. This is the topic of the next blog.
*Note: To simplify data collection, the company commissioned the development of iPhone and Android apps. The iPhone version of the app is available on the App Store (+12C Pro). The Android version hasn’t been published simply because of the expense in preparing the app for general use. But if there is interest, take a look at the online videos for the iPhone version and post a comment in the comments section for this blog. With sufficient interest, I can have it published on Google Play.
Fast charge 2.0, Samsung, Galaxy, Galaxy S9, Galaxy S10, are trademarks of Samsung Group. Xiaomi and Mi9 are trademarks of Xiaomi Corporation. App Store is a service mark of Apple Inc. Apple, iPad, iPhone, Xs are trademarks of Apple Inc. OtterBox and OtterBox Defender are trademarks of Otter Products LLC.