The stationary batteries, IMHO, are not needed in this mod. There are many other mods around that introduce temporary portable power sources which don't need water to run (to name a few - SMRs, AAI Industry (Burner generators), Battery Pack). There's nothing bad with your version, aside from aforementioned description problem, but players who are using different solutions for portable energy and are not that much thrilled about underground expansion might just pass this mod simply because this aspect doesn't sit well with their ideas of balance. Maybe it would be better to split Batteries into a separate tiny mod, link it as a recommendation in the mod's description and add as optional dependency?

Not to mention it would work both ways - players who don't want the Underground splinter mod still might enjoy the Batteries as a standalone version! I know I would. :3

These were part of the original, they are intended to be used to jumpstart the lowest level. I'm not taking into account what others have done though I may incorporate compatibility teaks along the way.
But yes they themselves could be splintered off but adding another mod to the list will just mean it's going to the bottom of the priority que.
Not sure the best strategy to implement but but the time I get to it it would be a required mod and there would be a bit of work alter both scripts.
It's an option for later consideration.