I'm really not convinced that closing the application is the right UX here, and I suspect that displaying an overlay (like we do when there is no SD card) would be the better thing to do.

In any case, this is the wrong place to call closeApplication.  The low battery controller should just emit the events and let other parts of the code respond to them. The right place to quit the application is probably in app.js though I defer to @wilsonpage for architectural design decisions like that.