On December 31, 2016, about 0740 central standard time, an amateur-built Gosselin Glastar airplane, N120CG, was substantially damaged during a forced landing near Lee's Summit Municipal Airport (KLXT), Lee's Summit, Missouri. The private pilot sustained serious injury. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no Federal Aviation Administration (FAA) flight plan had been filed for the flight. The flight had departed LXT about 0730 and was en route to Miami County Airport (K81), Paola, Kansas.According to the written statement provided by the pilot, his preflight inspection did not identify any problems. While attempting to start the airplane engine with the "A ignition system" the engine would turn over but would not start. The pilot switched to the "B ignition system" and had the same result. The pilot used a portable battery to "jump start" the engine; the engine started and ran within normal parameters. During the engine run-up, prior to takeoff, the parameters continued to indicate normal and the voltage indicated 14.2 volts. Several minutes after departure, the engine lost power. The pilot vaguely recalled trying to restore engine power but did not recall any of the events that followed. According to the FAA inspector who responded to the accident, during the forced landing the tailwheel struck the ground first followed by the main landing gear. The fuselage and both wings were substantially damaged during the impact. The airframe, engine, and related systems were examined under the auspices of the responding FAA inspector. The airframe was equipped with an "A", "B", and "AB" battery system; however, the batteries were in series and not parallel. The operation of the engine, fuel system, and electronic fuel injection system was dependent on electrical power from both batteries. The examination revealed that one battery had a short and would not take a charge. When that battery was replaced with a known serviceable battery, the fuel boost pumps, and alternator functioned as designed.