So I found a big 12V only marine charger. By the time I came the battery had come up enough where my smart charger was now pushing 12V into the battery. Returned charger 3 and put the charger on 5 amps for 5 hours and then to 3 amps over night for final charge. Came up to 100%. Had it loaded tested and it was 100% good. Reinstalled the battery in 10 minutes and she fired right up and is fine no issues.

Has anybody tried simply disconnecting the positive battery terminal in the trunk and leaving the trunk slightly ajar ( using a cloth to stop it closing and locking) during Winter storage?
I would not expect the battery to die when disconnected for a 3 month period, though it would likely benefit from a charge before reconnecting.

The issue is the battery needs to come out of the car to full charge according to Jag. Not exactly sure why because there is enough room to get at it. Just wrap the leads up so they don't contact the battery while charging the battery.

Makes no sense to me!!
Only thing I can think is Jag does not want to risk a high charge rate to the battery terminals being "back fed" to the car electronics.
Either way, just disconnecting the positive terminal would avoid any such risk while charging.
I guess it does mean you need to be very careful if you ever need to call out roadside service for a "jump start"!!

My Maserati has a battery switch so you can just turn off the system while charging. Simple and works great to protect the system. Battery in the truck too but they have a hidden key port for the trunk if you loose power.

I charge my battery in the car with a CTEK MXS 5.0 and haven't had any issues so far. I suspect Jaguar is protecting itself from warranty claims when a high rate charger fries all the modules. CTEK is nice and gentle.

Persistence does pay off. Now we shall have to wait and see what happens in a week or so.

I agree but its only $200 bucks and easy to do now. If I have an issue I will swap it right away. Don't want to get stuck somewhere.

AGM batteries will self discharge very slowly when new, but as they age, they will self discharge more quickly and may not hold enough charge to last three months. The negative cable is the one you need to disconnect, not the positive.