When you vape the Allo, the colour of the LED will indicate the battery level.
White: Your battery is between 70% and 100% charged.
Blue: Your battery is between 69% and 40% charged.
Red: Your battery is between 39% and 10% charged.
For optimize performance, the Allo LED light will flash 10 times and stop functioning when the battery is below 10%.  Your Allo battery may run out of charge before the Allo cartridge is finished so don't automatically discard the cartridge when charging the battery as there maybe E-liquid in it.