The ONLY decent way to do Amp Checks is with an Amp-Clamp type meter. Using a regular VOM meter is diabolical in such an operation.

 

Macc, if you can charge the battery fully outside the car and let it sit unhooked for a couple days. keep checking the voltage daily and see if it keeps dropping from an internal short.

 

I have the same problem on my 2010 XKR owned from new. 2 months new and the battery was dead. The dealer replaced the battery and no problem for the next 7 years then intermittently I would come to the car and find a completely dead battery. Had the dealer check it out, they indicated a parasitic drain on the audio system and a rusty ground strap. The software of the audio unit was reloaded and the strap replaced. I also changed the battery as it was 7 years old and winter was approaching. A few weeks later same thing. This time the dealer replaced the alternator as it was not charging when hot. This issue continues with no suggested solutions. Last year it came out of the garage in April after being on a battery conditioner all winter and ran smoothly until September, then the problem started again.

It is a random event and so difficult to check I appreciate but I am surprised there is no diagnostic tool to identify this type of event. They exist in other fields, e.g. power supplies. it is as likely to occur after a long run as after a shorter one but the discharge must be rapid as it goes from full charged to dead overnight.

I understand there is a built in battery conditioning circuit that monitors the battery and periodically puts it through a discharge cycle. Is that the case and if so is it software driven.

Another possible cause suggested by the dealer is the heated front or rear screen switching on, which can be checked by hand!
Sorry for the length of this but any guidance appreciated and it lets Gordocat know he is not alone out there.

 

Well that was not very comforting...situation seems to be same here :/ Have to test the parasitic currents anyway, and perhaps try to get the battery out for some days as Ranchero50 suggested.

 

I was also told my battery was good to go by a specialized battery shop. Battery would go dead in less than two days if not driven. Battery was toast, specialized shop was wrong. I put in a new battery and and installed a battery tender and no issue's in last 4 years.. Your car needs a new battery... just my opinion. Batteries are cheap, chasing your tail not so much.

 

What he ^ ^ ^ ^ said.
I had an F150 that I suspected either the battery or alternator so I took it to a shop. Then a different shop. Then an Autozone, and a different Autozone. Then an O'reilley's.
EVERY PLACE told me something different. I bench checked the alternator myself and found it somewhat bad, then I bought a battery tester and found the battery ALSO not in the greatest shape.
I replaced both, and it went another five years until I sold it.

 

well it is comforting to know you are not suffering alone ;-) I will have a long discussion with the dealer next week to try to identify possible causes and will keep you posted. I have learnt that locking the car should shut down all systems except the alarm, but my issue occurs even when th car is locked. Logically this suggests that the system is not shutting down as required, so maybe that is a starting point.

I also found a service bulletin dealing with 2010 -2012 xk vehicles where customers have experienced loss of starting capability, i.e. battery failure. I have attached it so you can see if it applies to you. I do not know if this was done for my vehicle, I certainly did not receive a recall letter, It does point to a software glitch in the battery monitoring system, which is the system that periodically puts the battery in discharge mode to monitor its performance I believe.

I would normally agree with the sentiment of checking the battery and replacing it, but in my case I experienced the problem after a new Jaguar OEM battery was fitted at the dealership, and after they subsequently refitted another new battery. In my case I think it is something more than a tired battery.

By the way, I have fond memories of a visit to Helsinki in 98. The Finnish countryside is so much like of the area of Canada that I live (Muskoka) with pink granite rocks, lakes and trees, etc. I thought I had forgotten to get off the plane!