Reference

Charge Indicator Status List

The charge indicator light

turns on or blinks differently according to conditions.

Lit in orange	The battery pack is charging. (Turns off when charging is completed.)
Blinks along with the green power indicator	The battery pack is running out of power. (Normal mode)
Blinks along with the orange power indicator	The battery pack is running out of power. (Sleep mode)
Blinks fast in orange	A battery error has occurred due to a failed battery pack or an unlocked battery pack.