Dead battery- what could it be?

[PLP]

9 years old...

I have the original battery in 2015 Audi Q5. The car was in CA for the first 3 years and since then in MI. Car has about 65k miles and no problems starting whatsoever.
It is parked for 2 weeks quite often with no interactions. Alarm is not armed.
So they may last longer...

As for you, what that could be?

Maybe a loose connection?
Can battery die all of sudden? Yes, the cell will short when you are driving and it will discharge quickly once parked.

If the battery was left completely flat for more than a week, it will be a toast. No charger will bring it back to life.
Yes, you could rinse it with DI water and charge it, repeat 3 times and then flood with acid. I had done it years ago. Worked. But nowadays - no access to cells. Plus getting sulfuric acid is not easy.

If you think you have a leak somewhere (current leak), you could use this gauge. I chased my daughter's car issues with it.
https://a.co/d/6YPXpbk

[MikeMcMo]

Originally Posted by PLP

As for you, what that could be?

Maybe a loose connection?

If the battery was left completely flat for more than a week, it will be a toast. No charger will bring it back to life.

Thanks for that! I won't go as far as to get the gauge- would need more background learning before i could make use of it.

btw FWIW it was a 5 year old Interstate battery and a night on the charger brought it back to life (for now). It was dead for between 6 and 11 days but I don't know when the short happened. Guess I should be glad it didn't burn down the car and the garage, but I guess that's one thing fuses do.

It turned out to be something under the passenger seat. Pulled the fuse for that and it stopped. Put the fuse back in, it started clicking again, but then I hit the seat adjusters and it stopped. I have to take the seat out and see if there's anything obvious I can see but I'm not optimistic, and I don't know if I could count on it not happening again and running down the battery at the worst time.
Hope to get to that soon.