As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: MID RIGHT EMERGENCY POWER SUPPLY UNIT BATTERY AND EXIT SIGNS FAULTS DISPLAYED DURING SYSTEM TEST. REPLACED BATTERY FOR THE MID RIGHT EMERGENCY POWER SUPPLY UNIT PER AMM 33-51-38 AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK WITH NO FAULTS NOTED.