Wireless charging already exists in various forms, but you still have to get your device pretty close to the charger for it to work. Innovations like Qi 1.2 promise to extend the range of wireless charging, but a team at MIT has unveiled a new wireless charging tech called MagMIMO. If this system can be perfected, you might not even have to take the phone out of your pocket to charge it — MagMIMO will simply detect the phone and project a cone of energy toward it to connect.
The version of MagMIMO current working in the lab can charge a phone from up to 30 cm away. That compares with a little over 1 cm with current Qi-compatible chargers, and 4.5 cm with the upcoming 1.2 revision of Qi. At 30 cm you could have a charging coil built into a desk or bedside table and simply put the phone down in the general vicinity of it to begin the charge. Standard wireless charging pads that use Qi or the competing PMA are notoriously finicky about where you place the phone — generally, it has to be right on top of the pad, dead center.
MagMIMO offers this level of freedom thanks to a technique borrowed from high-end WiFi routers. When a router detects a device attempting to connect, it can actually ramp up the signal strength and direct it toward the source of the the connection. That’s the same thing MagMIMO does, except it uses a magnetic field. An electromagnetic wave like a router puts out can cause heat build-up when focused strongly, but that’s not the case with a magnetic field. So MagMIMO should be safe, though I have to wonder if it could affect pacemakers.
As the field is focused on the target device, coils in the emitter vary their frequencies to reinforce the overall strength of the signal. Like other charging methods, a phone or tablet equipped with MagMIMO has receiving coils that convert the magnetic field back into electricity to feed into the battery.
The current rig is not what you’d call market-ready. It consists of an iPhone 4S with a receiving coil on the back. A wire lead connects up to the phone’s charging port to relay the power to the battery. Ideally, this entire system would be inside the phone, much like current Qi and PMA systems. The team found that MagMIMO was able to charge the iPhone from completely dead to full in about 5 hours.
So how does that compare to current technology? The iPhone 4S has a 1420 mAh battery, so that works out to roughly 284 mAh of juice each hour. At that rate, it would take eight hours to charge a Nexus 5 or almost ten hours to completely fill a Galaxy S5. Qi is limited to 5W/1A of output, making it about as fast as a low-power wall plug. It takes 2-3 hours to completely charge a modern smartphone with Qi 1.1. The new v1.2 pads will be even faster.
The goal with MagMIMO is to extend that 30 cm range — which is basically a proof of concept — to cover an entire room. You could simply walk in and sit down with the phone still in your pocket and have it charging. If the device is always suckling at MagMIMO’s magnetic teat, it doesn’t matter so much that it takes a long time to charge — it makes sure you never get into the danger zone in the first place. If researchers can get MagMIMO to that point, it’ll be like having WiFi for power.