As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
'BAT CHARGER APU' EICAS STATUS MSG DISPLAYED. APU BATTERY CHARGER FAILS. INPUT POWER TO APU BATTERY CHARGER GR IS OFF OR FAILS. APU BATTERY CHARGER INTERLOCK IS OPEN. APU BATTERY IN OVERHEATED CONDITION. REPLACED APU BATTERY AND CHARGER.