On February 25, 2017, about 1115 eastern standard time, a Socata TB20, N2519T, was substantially damaged during a gear up landing at Melbourne International Airport (MLB), Melbourne, Florida. The private pilot was not injured. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the flight, which departed Key West International Airport (EYW), Key West, Florida, about 1012.The pilot reported that during his cross-country flight he noticed the alternator warning light flash and the battery began to discharge. He contacted air traffic control, but did not declare an emergency, and began a slow descent while initiating the emergency gear extension. After multiple unsuccessful attempts the pilot performed a gear up landing. An examination of the airplane by a Federal Aviation Administration Inspector revealed that the main landed gear was extended but not fully locked. The nose landing gear did not extend and remained in the wheel well. Examination of the airframe revealed that the bottom forward bulkhead was damaged during landing sequence. An examination of the nose gear assembly revealed the circlip on the nose landing gear strut was dislodged from the nose landing gear leg assembly, which allowed the strut to extend further than usual. The circlip used to retain the nose gear strut inside the nose gear assembly had paint on the outer portion of the circlip, which should have been fully set inside the groove used to keep the circlip in place. An examination of the circlip groove revealed that it was in serviceable condition with no corrosion or other deformation within the groove. A review of the maintenance records showed that the nose strut was disassembled and repaired on July 15, 2015, and the airplane was completely repainted on April 5, 2016. Further review of the maintenance records revealed that since the disassembly of the nose gear, a total of 75 hours of flight time had accumulated since the maintenance. According to the airplane's maintenance manual the, nose landing gear strut retaining circlip should have been fully installed in the groove. After it is installed, the landing gear should be rotated several times to confirm proper installation.