As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED. DURING OPERATIONAL TEST OF EMERGENCY LIGHTS HAD BATTERY FORWARD LEFT FAULT MESSAGE. MAINTENANCE REPLACED BATTERY FOR EMERGENCY POWER SUPPLY UNIT 10WL AT THE FORWARD LEFT DOOR IAW AMM 33-51-38 AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK.