As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING SERVICE CHECK, MAINTENANCE FOUND THE COCKPIT EMERGENCY LIGHT TO BE INOPERATIVE. TROUBLESHOOTING LEAD TO A DEFECTIVE BATTERY IN THE POWER PACK REF AMM 33-53. BOTH BAD CELLS IN THE BATTERY PACK WERE REPLACED. OPERATIONAL CHECK WAS GOOD.