As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A HEAVY CHECK, AFT CABIN EMERGENCY LIGHTS FAILED TO ILLUMINATE WITH THE SWITCH IN ARM AND THE 1WEL AND 2WL CIRCUIT BREAKERS PULLED. R & R THE BATTERY PACK 13WL IAW AMM 33-51-38-000-002-A, AND 33-51-38-400-002-A. OPS CHECKED GOOD IAW AMM 33-51-00-710-004-A.