So I'm just trying to use the mod. I got it installed fine and built a water mill, connected to a LV battery box, like so:

The water mill seems to be working, it says "Production at 100%":

Yet the battery box sits there saying "Idle" and not charging. Doesn't change if I add any objects into it:

I also tried replacing the water mill with a coal generator, but the battery box was not powered either (the generator did play the burning animation though).
What am I doing wrong here?
P.S.: I am new to Minetest/Minecraft-like games in general, I may be doing something very stupid.
EDIT: Inserted working image links. --Vanessa