Based on the description on their site, the controller includes a built-in battery: "8.39 Wh Li-ion battery, 35+ hours of gameplay... "
That was disappointing for me. Specially condidering the Steam Frame's controllers make use of AA batteries: "One replaceable AA battery per controller, 40hr battery life"
AA Batteries might not be as convenient to use, but being able to replace them is a great advantage. All my Xbox360 controllers still work fine, but none of my PS3' Dualshock 3s.
The official docking station could be used to recharge (rechargables) AA batteries so the functionality could remain the same.
I own an 8BitDo SN30 Pro+ controller that has a neat feature: It comes with a rechargeable battery back that is user replaceable via a simple back cover, but regular AA batteries can also be used in the same slot instead.
Kinda like an Xbox controller, except that the rechargeable battery was actually included instead of being a separate purchase, and no adapter is needed for either battery types.
I don’t recall the Xbox rechargeable battery pack requiring an adapter. It just pops in where the AAs would be.
Pardon me, I realize I was a bit vague in my statement. I think what I was referring to was specifically the Xbox 360 wireless controller.
If I remember correctly, AA batteries didn't quite fit directly in the controller. Rather, they fit inside a small detachable casing designed specifically for their cylindrical shape, which was then clipped onto the underside of the controller. If you then purchased a rechargeable battery pack, it replaced that attachment entirely, clipping directly onto the controller in its place.
I had totally forgotten about that, but you’re right.