Walt This is a pretty interesting idea, either as a requirement for stealth or just as a way to hide from long-range radar. I like that it makes having a large battery reserve more important and the determining factor of how long you can stay stealthed.
I like how shutting down your generators makes your dot disappear, and you run on reserves. That would be awesome.
Ideally you would also need to shut off engines, but going "silent running" conflicts with space drag unfortunately.
Anyways, yes this! it's a nice tactical option. Maybe with a turn off/turn on all generators button?