If your scooter battery gets down to 0% The BMS which is the battery management system will go into the sleep state which means the normal wall charger that you would use will no longer properly charge the battery.
Solutions:
You could potentially leave it plugged in for 8,10,12 hours and when you pop the thing off of there the battery is still showing that it's dead because you have taken the battery down so far that it's beyond its ability to charge back up.