Xiaomi has teased a new 40W wireless charger it claims can fully charge a phone with a 4,000mAh battery in just 40 minutes. For context, it takes about four hours to charge an iPhone 11 — which has a 3,000mAh battery — using a conventional Qi wireless charger, so Xiaomi's solution could cut that down to 30 minutes. If the iPhone supported 40W wireless charging, that is.
Fast wireless charging could actually be useful — In a timelapse video shared by Xiaomi's vice president, Chang Cheng, you can see a Xiaomi phone charge to 57 percent in 20 minutes, reaching 100 percent in 40 minutes. That would be pretty great if the solution actually makes it beyond teasers to a production release. The biggest black mark against wireless charging to date has been how sluggish it is compared to wired charging, relegating it to use for overnight charging for many people... and even then, you have to make sure you've actually put it on the charging pad correctly or so much for your morning alarm going off.
The problem is device support and battery capacities — Today there aren't any phones on the market that support 40W wireless charging. Apple's iPhones max out at a pretty dismal 7.5W, Samsung's latest phones top out at double that (15W), and even Xiaomi's own Mi 10 Pro has an upper limit of 30W wireless charging.
Xiaomi has said that engineering a phone capable of charging at such fast speeds is tough. The biggest issue is the trade-off between faster charging speeds and the lower overall battery capacity they require, which is something few consumers are likely to accept. According to testing by the company, a 100W fast-charging battery can hold about 20 percent less charge than one capable of 30W wireless charging.
Heat is also a challenge — Earlier this year, Xiaomi VP Lu Weibing outlined a couple of other issues that are holding fast charging batteries back from reality, like concerns around overheating. Regulating heat from high voltages was reportedly one of the key reasons Apple shelved its AirPower wireless charging mat.
The teaser from Xiaomi doesn't bring phones that support 40W wireless charging closer to fruition, but it shows what's possible with the technology. And if anyone's working on a phone to support the tech, it's probably Xiaomi. We're very ready for the rapid wireless charging future. Let's hope phone makers share our enthusiasm.