As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A HEAVY MAINTENANCE CHECK, THE OVERWING EMERGENCY POWER SUPPLY FAILED FROM THE COCKPIT TEST PANEL. REMOVED AND REPLACED EMERGENCY BATTERY SUPPLY PACK AT OVERWING STATION IAW DC10 MM 335101. BATTERY PACK TESTS GOOD IAW DC10 MM 335101.