When the device is on press the fire button, the LED light will indicate your device’s current charge.

When its current charge capacity is above 3.8 volts the indicator light will be blue and red.

When the charge is between 3.8 and 3.5 volts the light will be blue only.

When the charge drops below 3.5 volts the light will then become red to remind you that it is time to charge your device.