Microsoft has filed a patent for a Stylus Battery Charging System

A patent for a stylus charging mechanism, was filed by Microsoft on New Year’s Eve 2015, suggesting that future iterations of the Surface Pen will replace the current design powered by triple-A button-cell batteries, with a rechargeable, Lithium battery.

The current embodiment of the Surface Pen claims up to one year of continuous operation, on a set of three triple-A batteries alone. While this might be true, there are is a rather important reasons for Microsoft to switch the Surface Pen to a rechargeable Lithium battery: namely the life of the cell-battery itself.

All batteries self-discharge, and given enough time, they will leak acid inside the host device if left inside for too long, eventually damaging the battery casing and nearby connectors and circuitry. While the effects of self-discharge of a battery as small as the button-sized triple-A cell required by the Surface Pen may not have effects as dramatic as previously described, cell batteries are still not a viable way to power devices in the long term.

Fortunately, the Surface Pen is not as expensive to replace as the Apple Pencil, which makes it easier to upgrade to a newer version which will most likely be compatible with current iterations of the Surface Pro and Surface Book.

The charging dock of the new Surface Pen design is covered extensively in the patent, with a number of different methods for the Pen to attach and charge. Some of these embodiments can reflect a dock that could even detach itself, and connect to compatible devices via a standard port, like a USB Type-C connector, a USB 3.0 port, or even a wall outlet. Some versions may integrate magnets to hold the stylus in place, while other may employ a ring, or other mechanical constraint.

While a rechargeable version of the Surface Pen might come with a slightly higher price tag, the benefits will be in terms of longevity of an accessory that will hopefully backward compatible.

While it’s easy to assume a resemblance with the Apple Pencil’s design, Microsoft’s patent was originally filed in June 27 2014, which pre-dates both the iPad Pro and the Apple Pencil.