As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED DUAL ALTERNATOR FAILURE IN FLIGHT. USED EMERGENCY: BACK UP ESSENTIAL PATH AND BATTERY DID NOT PROVIDE POWER. BOTH ALTERNATORS, LH/RH POPPED CIRCUIT BREAKERS. MAINTENANCE INSPECTED AND NOTED THE LEFT ALTERNATOR PULLEY WAS LOOSE AND THE ALTERNATOR BELT DAMAGED. THE BELT WAS REPLACED WITH NO FURTHER DEFECTS NOTED.