lack of power

Hi All, Finished building my F450 today, Naza Lite with my Turnigy 9x TX and RX. Motors are DJI 2212/920KV with 30A ESCs with stock dji props (8045), battery is a turnigy 2200mah, voltage alarm showed cells as full. First flight in back garden was great, so we took it to the beach. On take...