As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: FOUND EMERGENCY POWER SUPPLY UNIT BATTERY FORWARD LEFT FAULT ON PERIODIC SERVICE CHECK. MAINTENANCE REPLACED BATTERY AT EMERGENCY POWER SUPPLY UNIT (10WL). ALL CHECKS NORMAL. OK FOR SERVICE. REFERENCE AMM 33-51-38.