Currently, there is no battery level indicator for the controller. It would be great if there were a little battery indicator in the Stadia side menu next to the Controller icon. That way players could tap the Stadia button, get the slide out menu and quickly check the battery/charge of their controllers.
that sounds really helpful indeed. 🙂 Did you already send feedback to the Stadia team using the mobile app? I hope this feature will become reality soon!