As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU AUTO SHUTDOWN AND UNABLE TO APPLY POWER TO AIRCRAFT. FOLLOWING APU BATTERY AND APU BATTERY CHARGER REPLACEMENT PROBLEM PERSISTS. AFTER TROUBLESHOOTING MAIN AIRCRAFT BATTERY REPLACED AND POWER RESTORED TO AIRCRAFT. GROUND POWER AND APU POWER OPERATION NORMAL. BATTERY BORROWED PART FITTED. PART NR 4579, SERIAL NR 066068 MAIN BATTERY POSITION.