They have to change whats on shelves and distances between items all the time. So changing batteries isnt all that uncommon.They also are pretty power effecient since the displays are e-ink Edit: also we have a box of batteries in the back. If we notice a whole rail isnt displaying properly we can go grab a new one and have it switched out in like 2 minutes.

Yeah they break way too easily. I swear half the ones on the bottom shelf are wrecked from carts hitting them where i work.

They run off batteries. Usually an entire rail has one battery for all the tags. But they only need to use power to change the screen. I forget the type of screen but its like digital ink? They usually refresh and maybe change price around midnight where i work. They do run off of something wireless but hell if i know exactly how it works.