As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EMERGENCY LIGHT TEST FAILED. SHOWS EPSU 28VDC EMER L. SUPPLEMENTAL DATA UPDATE 28 VDC FAULT WAS DETECTED AT THE EMERGENCY POWER SUPPLY UNIT (11WL) AND GAVE A FAULT MESSAGE 'EPSU 28 VDC EMER L'. THE BATTERY WAS REPLACED AND THE TEST WAS FOUND NORMAL.