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 LIGHTS CONNECTED TO EMERGENCY POWER SUPPLY UNIT BATTERY PACK NR 3 INOPERABLE. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE NR 3 BATTERY AND CHARGER IAW CRJ WC 33-002. THE OPERATIONAL CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.