2002 Jaguar XKR replace battery - idle wont sustain

Car is rarely driven (obvious from miles). I ususally keep a trickle on the batter, but it got mistakenly unplugged. So recharged battery and reset windows.
Car will start but runs rough and dies after about 5 seconds. Have tried all throttle settings.
Read post about reset idle, but car won't run long enough. Car has been sitting for about six months. 5