Why does it need a power cable? To me the main selling point of e-ink displays is that they should be able to last weeks if not months on a single charge...
I want to make a version with a battery. But I don't know when I will get this done. My goal is to make it last at least half a year. 6 months I think is the minimum standard for a thing that is supposed to hang on the wall and not be a hassle to babysit.
A battery adds a lot of complexity and cost for testing, certification and shipping. And it adds another failure mode.
So I decided against it for the current version.
