As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AIRCRAFT WAS IN MAINTENANCE IT WAS DISCOVERED DURING TEST THAT SEVERAL OVERHEAD AND OUTSIDE EMERGENCY LIGHTS DID NOT TEST. MAINTENANCE FOUND POSITION 300 POWER SUPPLY WITH GROUND WIRE BROKEN AND ASSOCIATED BATTERY OVERHEATING. BOTH WERE REPLACED BUT PROBLEM STILL EXISTED. SUSPECT OTHER BATTERIES WERE AT FAULT, AND ALL BATTERIES WERE REMOVED AND RERPLACED, OPERATIONAL CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.