The board's LED lightbar will blink once (the Onewheel+ XR doesn't have a lightbar, so the power button will blink once instead) to indicate low battery; the board will go into error 1 and the app will send a notification saying it "Needs Juice" when the board does not have enough power left to run properly.
If you run out of battery while riding a Onewheel, it will give you extreme pushback/Haptic Buzz until you dismount the board. Failure to respond to extreme pushback and continuing to ride the board could lead to the board powering off. Once dismounted the board should not be ridden until it is at least partially recharged.
If your board continues to give you this error after fully charging, we recommend you contact us so we can help you out.