Suddenly dead battery

2008 /cadillac CTS. All maintenance up to date. Parked for 1 1/2 hours for dinner - weather 78 degrees and clear. Came out and car battery completely dead. No radio, lights, etc were left on. Jumped by AAA and works fine. Battery relatively new. This has happened now three times in three years. Taken to dealer after episode 1 - found nothing wrong. Taken to NTB after episode 2 - found nothing wrong but made a few minor adjustments. No one seems to be able to figure out what makes the electrical system completely drain in minutes. Any ideas???


“Taken to NTB”

Who is NTB ?

I assume you have no parasitic draw?
Has this been verified?
Has your charging system been tested?
Do you drive only very short distances?

“Battery relativey new”

Please clarify

1 year old
6 months old

“made a few minor adjustments”

please clarify

I would have the battery “load tested” before I assumed it was a good battery. A simple voltage check with a voltmeter will not suffice if it’s a problem battery.

Power connection problems between the battery and the ignition switch and even with the switch itself can make you think there is a battery problem. I suggest you carry a test light probe with you so you test some things the next time this happens. Also find out how power is connected from the battery to power panel under the hood so you can check things there using the probe. There should be a main fuse in the panel that supplies power from the battery to all the things inside that panel that can be checked using the probe. Another quick check that can be done is to see if the brake lights work. They are tied to power directly and if they don’t light up there are just a few possible places the trouble can be at between the panel and the battery.