I have had my 2008 Jaguar XK for over a year now. During this time, I have had many of the usual electrical gremlins Jaguars seem to suffer from. In the case of later model Jaguars (like mine) virtually all the gremlins are in some way related to the car's battery ending up in a state of discharge. I have come up with some suggestions to keep your Jaguar's battery healthy and reliable...

1. When you pull your modern day Jaguar into the garage and shut it off, the car is not truly "off". In reality, there are all sorts of computers computing, radio transmitters transmitting, and gizmos "gizmoing". All these things pull major juice out of even the strongest battery. The way to get most of this stuff to turn off (go to sleep) is to lock the door via the electric door lock button. This might seem like a "no brainer", to most folks, but in my case, I live out in the country. I have NEVER locked any of my cars out here. So, in the case of my XK, for 25 minutes or more after parking the car, all the electrical stuff kept doing their thing until finally the battery saver circuit kicked in and shut everything down. By that time, the battery was weakened. After a few days of this, the battery was well on its way to dead. I now lock the doors everytime I get out of the car anywhere, including home.

2. If you get the battery replaced MAKE SURE the dealer "flashes" the ECU, or the car will not "talk to the battery" the way it should. This also causes dead batteries.

3. If you are leaving the car for more then a week or so, put the car on a battery tender and MAKE SURE you do NOT attach the negative side of the tender directly to the negative battery post. This confuses the ECU. You must attach the ground side to the body of the car (The spare tire post in the trunk is a good place.

I have a few more things to share, but the grill is hot and my wife wants her steak well done...More later...

 

Many modern day automobiles share the battery drain you're experiencing. I had a couple of Lexus' that would do the same thing--and required keeping the doors locked. They too would run the battery down after a couple of weeks.

I would suggest you get a multimeter, and go through all your fuses one by one (with the car sitting for awhile) to figure out where the drain is going. You might have to tape up the door post switches that turn on courtesy lights. After you identify the problem area, you'd need to diagnose that individual circuit. Sometimes, it's something like a burglar alarm--or something that can be disconnected or deactivated.

If you replace a battery or if the battery is completely discharged, your engine usually "relearns" its settings in a short amount of time. Auto parts stores have a 9 volt battery hooks up to an accessory plug to use when replacing batteries--that holds current engine settings.

I too am a believer in Battery Tenders, and keep my battery hooked to one if it's not going to be driven for a week or two. They're great things to have on lawn mowers, boats, etc.

Sorry you had a hot grille, and your wife was wanting her steak. I've got to close up shop because my wife's hot, and she's wanting her steak.

 

Thanks for your inputs guys ,keep them coming