As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, THE CREW RECEIVED A NR 2 MAIN BATTERY OVERHEAT CAS MESSAGE AND RETURNED TO BNA. MAINTENANCE WAS DISPATCHED, INSPECTED, AND REPLACED THE NR 2 MAIN BATTERY IN ACCORDANCE WITH DORNIER MAINTENANCE MANUAL 24-00-00. OPERATIONAL CHECKS WERE PERFORMED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.