A light-emitting diode (LED) lighting system comprising a luminaire and a power pack is used to replace the luminaire operated only in a normal mode with alternate-current (AC) mains. The luminaire comprises LED arrays and a power supply whereas the power pack comprises a rechargeable battery, a charging circuit, an LED driving circuit, and a self-diagnostic circuit. According to availability of the AC mains, the LED lighting system can auto-select to work in an emergency mode when a line voltage from the AC mains is unavailable. The self-diagnostic circuit comprises multiple timers and multiple detection circuits and is configured to provide a sequence and to auto-test battery charge and discharge current according to the sequence. In another embodiment, the luminaire power pack is integrated into an enhanced LED luminaire to support such dual mode operations.