Flashback: a decade of Xiaomi battery and fast charging technology
Battery charging is one of the few remaining segments of the smartphone world where proprietary technologies can thrive. Most companies use chipsets from the same vendors, they also buy the same screens and camera sensors. But batteries and accompanying hardware are sometimes entirely custom, and have been an area of rapid innovation in recent years.
Granted, USB Power Delivery exists, some might say it’s the best option due to its wide support. The same argument can be made for Qi on the wireless charging front. But today, proprietary systems allow higher speeds and are used in some exceptional devices.
A simplified diagram of how fast charging systems do what they do
This week we wanted to see how battery and charging technology has evolved over the last decade, and we will focus on Xiaomi. We will mainly look at the averages, but we have also included maximum values, as they also tell an interesting story.
The best of Xiaomi: 120W fast wired charging • 67W wireless charging
We often hear people say “give me a big battery even if the phone is thick”. For better or worse, neither Xiaomi nor other smartphone manufacturers seem to agree with this sentiment. As you can see, the average thickness of Xiaomi phones steadily decreased for a while and then stabilized around 9mm. However, the average battery capacity has increased even more over time due to improved technology.
These ever-larger batteries would take longer and longer to charge on the 10W USB cradle, so something had to change. Xiaomi’s first fast-charging phone was the Mi 3 (2013), which used Qualcomm’s Quick Charge 2.0 to do 18W. In fact, Xiaomi has used QC for several of its phones. For example, the Mi 9 Pro (2019) featured QC 4+ and did 40W wired charging and 30W wireless charging.
But Quick Charge couldn’t keep up, and Xiaomi phones with the highest charge ratings switched to a proprietary solution. As we mentioned in the opening, this is one of the areas where companies can stand out with in-house technology, for example the Surge P1 charging chip.
Battery capacities have not increased indefinitely. A few years ago Xiaomi had a Mi Max series, which had big screens and big batteries. The second model had a 6.44-inch screen and a 5,300 mAh battery. The third came with 6.9 inches and 5,500 mAh. But those weren’t the biggest batteries in the business, no. Instead, phones like the affordable and not-too-big Poco M3 pack 6,000mAh batteries (the M3 measures 162.3 x 77.3 x 9.6mm and weighs 198g). 6000 mAh is the highest level ever reached by Xiaomi.
Some interesting things we noticed while investigating the data. 2018’s Mi Mix 2S was the first Xiaomi to support wireless charging, it was rated at 7.5W. The company also released its first official Qi charger with the phone. The Mi Mix 3 from the same year was slightly faster with 10W support.
And from there it took off: 30 W in 2019, then 50 W, then 67 W, then… nothing. At least not yet. But we are halfway through the year and Xiaomi has yet to release a new phone that supports wireless charging.
What happened? The Mi 11 Ultra brought parity between wired and wireless charging, both rated at 67W. Sure, wired charging is more efficient, but not as efficient as you might think. Comparing with wired and wireless, charging times from 0-100% are 36 minutes and 39 minutes.
Still, the company’s focus appears to have shifted to wired charging. Phones like the Xiaomi 11i HyperCharge 5G only exist to offer users the option of 120W super fast charging: in our test, a full charge from 0 to 100% was completed in 16 minutes. 22 minutes if you have disabled Boost mode to save battery power. Meanwhile, only a few models released in the last two years support wireless charging of 50W or more.
How fast can charging technology go? When it comes to the USB-C cable, there’s a lot of leeway. The latest USB Power Delivery specification offers a whopping 240W. Xiaomi itself introduced a 200W charger a year ago. And it has an 80W wireless charger. We expect to see charge rates continue to rise for at least a few more years, particularly the average charge rate.
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