Drove the car to the grocery store this morning. Fired right up as always. No hint of problem. Window bumped down and back up like supposed to when opening/closing door. I know when it does not bump back up that can indicate a weak battery; but worked fine. Drove less than 2 miles to store. No problem. Came out of grocery store - say 20 minutes later. Car completely dead. No lights, no accessories, no clicks, nothing. Tried to jumpstart, lights and accessories came on, but not enough juice to crank. Took battery back to parts store. It's only 3 months old. The tester showed it is good. Any ideas? Heading back to Publix to reinstall the battery and if it does not start, guess I'll have to tow it. So will very much appreciate any ideas. Luckily there is a Jaguar repair shop nearby. Unluckily they are big $$.

 

Check the ground and main power straps. Make sure they are clean and tight.

 

Mine did the exact same thing, turned out to be the main battery ground strap. I got one from an auto parts store for $10 and have had no more issues. Might have been connections, who knows. I had been experancing a lot of and frequent after cleaning, corrosion on the negative battery terminal before this happened.

 

Thanks for the suggestions.
Autoparts store tested the battery and said it was fine. Suggested roughing up the leads before reinstalling. They looked good to me, but did as suggested. Reinstalled battery. Fired right up. Go figure.

 

The crimp on the battery leads is a known problem. Moving them around may have improved the connection temporarily, so inspect them carefully.

 

Check your alarm system.

I've had this happen to me with my truck. The battery in my key fob was going dead, and wouldn't deactivate the kill switch (or whatever it's called)