As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOST GROUND POWER AFTER PARKING EMERGENCY EXIT LIGHT AT MID CABIN ISLE WAS NOT WORKING WHILE ON EMERGENCY POWER. WORKS FINE WITH NORMAL POWER. R & R THE ESPU AND EMERGENCY LIGHT BATTERY. SHOWED EVIDENCE OF A CELL THAT HAD SHORTED AND BURNED. FAULT REMOVED IAW AMM 33-51-38.