how do you know when elf bar is finished charging

When the bar is finished charging, the toy should be fully functional and ready for use. You can check the charge level by observing the red lights on the toy. If the red lights are glowing, it means the toy is fully charged and ready to go. However, if the lights are dim or not lit at all, that means the charge is low or depleted. In this case, you should connect the toy to the charger and let it charge for a while until the lights are fully lit again.