As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: WHILE ACCOMPLISHING J/C 26L00025011 WHILE PERFORMING OPERATIONAL TEST OF EMERGENCY LIGHTING SYSTEM. FAULT OCCURED TO REPLACE THE BATTERIES ON ESPU 12WL. MAINTENANCE REPLACED BATTERY 12WL EPSU IAW AMM 33-51-38.