As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BATTERY 1 OVERTEMP EICAS MSG DISPLAYED DURING CRUISE. THE CREW MADE A DIVERSION & THE ACFT LANDED SAFELY. TROUBLE SHOT & THE BATTERY WASN'T HOT, SUSPECTED TEMP SENSOR FAULTY. REPLACED NR 1 & 2 MAIN BATTERY. RETURNED THE ACFT TO SERVICE.