Microsoft filed a patent for a rechargeable stylus. This could mean that the Microsoft Surface Pen stylus will be rechargeable in the near future. The patent also includes details of a charging cradle.
The Surface Pen stylus' battery life is actually rated to last a year. The battery inside the stylus is non-rechargeable so users will have to buy a new a battery to power it. This seems like a non-intuitive method in powering the device because rechargeable batteries have been dominating majority of the modern portable electronic devices.
Microsoft filed a patent for a rechargeable stylus and its accompanying charging cradle. The patent drawings seem to feature a stylus similar to that of the Surface pen.
There is a drawing tip, an erase, and the power button situated on the side of the pen. The stylus' metal contacts will be the ones facilitating the charging. The pen is magnetically attached to the cradle during charging phase.
Microsoft filed this patent application in June 2014. As of this writing, there are no further reports when will this technology be applied to the Surface Pen. It is not even known, like every other patent application, if this technology will ever surface in the consumer space.
However, this is most likely applicable to the Microsoft Surface Pen in its next iterations. The Surface Pen is currently powered with either triple A or button cell battery.
One of the advantages of having a rechargeable battery, other than the obvious convenience, is it is more environment friendly. Fewer disposed batteries mean fewer batteries in the landfill. These items are known to be very toxic.
Apple's Pencil stylus for the company's iPad Pro has a battery life of 12 hours before it needs charging. This may not sound attractive, but it is still better both for the customers and the environment than Microsoft's solution.