As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING MAINTENANCE INSPECTION WHILE THE RAMP CONNECTED THE GPU THE EMERGENCY LIGHTS DRAINED. THE SWITCH IN THE COCKPIT WAS OFF. THE AIRCRAFT WAS REMOVED FROM SERVICE. FOUND NR 3 & NR 4 EMERGENCY BATTERY TO BE DRAINED. REMOVED AND REPLACED THE NR 3 & NR 4 BATTERY AND CHARGER ASSEMBLY. THE OPERATIONAL CHECK WAS GOOD IAW 33-700-19. THE AIRCRAFT WAS RETURNED TO SERVICE.