Originally Posted by jaglover922

I Know what your problem is but I'm not going to tell you. Techs within the Jag community keep info to themselves, so unless your battery is bad, then there is a drain. But chances are your battery is straight up bad. Jaguar doesn't make their own batteries. There is really only a few battery manufactures in the world. They just slap different stickers on the batteries. How often do you drive the car anyway? Does it sit? Was it sitting for more then a few days before you started it?

Originally Posted by jaglover922

I also don't want to reveal info so that you would not have to take your car into the dealer or Jaguar Specialty shop for work.

Originally Posted by jagular

The state of the original battery is not affected by jumping. Any jumper cables are connected in parallel to the car battery and no current passes through the dead battery. Any charging happening would feed both the dead battery and the jumper battery simultaneously. The jumper battery cannot charge the car battery.

If the engine won't turn over with a jump from a known good battery then your problem is with the starter or its wiring. The alternator is never relevant to a fail to start except if it is the cause of the dead battery. A failed alternator will not prevent the engine from starting and running.