As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB, CREW RECEIVED A (AUX BAT HOT) WARNING MESSAGE, THE BATTERY TEMP MONITOR CONFIRMED THE OVERHEAT AND THE AUXILIARY BATTERY SWITCH WAS TURNED OFF. AN EMERGENCY WAS DECLARED AND THE ACFT LANDED WITHOUT FURTHER INCIDENT. AUXILIARY BATTERY WAS FOUND VERY HOT, A GENERAL VISUAL INSP OF THE BATTERY COMPARTMENT REVEALED NO EXTERNAL DAMAGE. BATTERY WAS REPLACED AND THE ACFT RETURNED INTO SERVICE.