As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A ROUTINE OVERNIGHT SERVICE CHECK INSPECTION, MAINTENANCE REPORTED A PORTION OF THE EMERGENCY LIGHTS WOULD NOT TEST. MAINTENANCE REMOVED AND REPLACED BATTERY PACK IN POWER SUPPLY. OPS CHECK WAS ACCOMPLISHED PER AMM 33-50-00, SYSTEM OPS CHECKED NORMAL. AIRCRAFT RETURNED TO SERVICE.