Hi there ,
here's my 2 pennyworth
as I understand if you have a flat battery and need to jump start ::immediately the car starts you have to load the alternator via the battery, to do this put all the electrics on ( headlights, heater , wipers,heated windows ,indicators, rear fogs,front fogs) this loads/sets the alternator and tells it to put in a high amount of charge.
This info is in the car manual.
Regards