Battery charging is one of the few remaining segments in 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 the hardware that goes with them are sometimes completely custom, and have been an area of rapid innovation in recent years.
Okay, USB Power Delivery does exist, some might say it’s the better option due to its wide support. The same argument can be made for Qi on the wireless charging front. But currently, proprietary systems allow higher speeds and are used on some exceptional devices.
A simplified diagram of how fast charging systems do what they do
This week we wanted to look at how battery and charging technology has evolved over the past decade, and we’ll be focusing on Xiaomi. We will mainly look at averages, but we have also included maximum values as they also tell an interesting story.
The best of Xiaomi: 120W wired fast 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 makers seem to agree with this sentiment. As you can see, the average thickness of Xiaomi phones dropped steadily for a while and then stabilized around 9mm. However, the average battery capacity has further increased over time due to improved technology.
These ever-larger batteries would take longer and longer to charge to the 10W USB base, 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 performed 40W wired charging and 30W wireless charging.
But Quick Charge couldn’t keep up, and Xiaomi phones with the highest charging 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 5300 mAh battery. The third came in at 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-huge 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 achieved by Xiaomi.
A few interesting things we noticed while digging through the data. The Mi Mix 2S from 2018 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 of the same year went a bit faster with 10W support.
And it took off from there – 30W in 2019, then 50W, then 67W, 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 wired to wireless, charging times from 0-100% are 36 minutes and 39 minutes.
Even so, the company’s focus seems to have shifted to wired charging. Phones like the Xiaomi 11i HyperCharge 5G only exist to give users the option of super-fast 120W charging – a full 0-100% charge was completed in 16 minutes in our test. 22 minutes if you have disabled Boost mode to save battery power. Meanwhile, only a few models released in the past 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 plenty of headroom. The latest USB Power Delivery specification offers a whopping 240W. Xiaomi itself presented a 200 W charger a year ago. And it has an 80W wireless charger. We expect to see charge rates continue to climb for at least a few more years, the average charge rate in particular.