The aerodrome caretaker had been requested to inflate a tyre on one of the operator's aircraft. The engines of VH-IGT were operating when the pilot observed the caretaker approaching, carrying a battery which powered an air pump. The caretaker walked around the tail of the aircraft, placed the battery near the right wheel, moved to the wing tip and proceeded towards another aircraft. He then realised he had taken the battery to the wrong aircraft and returned, walking directly towards the right engine. The pilot attempted to shutdown the engines but the caretaker continued forward and was struck by the rotating propeller.