As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
YQM - INFLIGHT LHR-ORD. CREW REPORTED MAIN SHIP BATTERY SMOKING. EMERGENCY DECLARED FLIGHT DIVERTED YQM LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED MAIN SHIP BATTERY AND CHARGER. INSPECTED MAIN BATTERY CONNECTOR AND NO DAMAGE NOTED. SYSTEM GROUND CHECK NORMAL OPERATION.