As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING MAINTENANCE INSPECTION FOUND THE NR 1 EMERGENCY POWER SUPPLY UNIT BATTERY NEEDED REPLACEMENT. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE NR 1 BATTERY ASSEMBLY IAW WC 33-700-19. THE OPERATIONAL CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.