As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GNDED. FWD LT EMER POWER SUPPLY UNIT BATTERY FAILS BITE CHECK WHILE ACCOMPLISHING THE EMER LIGHT SYS CHECK. REPLACED FWD LT EMER POWER SUPPLY UNIT BATTERY & ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK IAW AMM 33-51-38.