What was found
IAH- MAINTENANCE, WHILE INSPECTING THE ARICRAFT THE MECHANIC NOTED THAT THE LOWER CENTER EMERGENCY LIGHTS FAILED TO ILLUMINATE. IAH- MAINTENANCE REMOVED AMD REPLACED THE #2 (TWO) EMERGENCY BATTERY, PERFORMED A OPERATIONAL CHECK OF THE EMERGENCY LIGHTIBG SYSTEM,NO DEFECTS NOTED, AND, THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.