Battery dead after two weeks of leaving it parked?!?

My battery has been fine on my Cayman for the 2.5yrs I've owned the car. It only died once and that was over 4 months ago, a jump-start fixed the problem. I parked my car for 2 weeks last week and when I came back the car struggled to start (as though the battery was too low). I drove it to a couple of places and then it officially died and wouldn't start. I jumped it off and then drove it for about 20 minutes to charge the battery up. The car then sat for a day-and-a-half and I just tried to start it and no dice. What could be killing the battery ?!? I have no other devices that would cause a drain and nothing has changed in the car setup. Could a battery just "die" after a couple of weeks of sitting there after years of good service?!? Do I need a new battery ?

I think what happens in some of these cases, is that these cars are constantly drawing some power (albeit a small amount if you don't leave your doors locked or items plugged in the 12V outlets). If you don't regularly drive your car for more than short jaunts, and leave it sitting for days to weeks at a time without a charger, then I think the battery reserve gradually spirals downward until one day, it doesn't work. Unfortunately, driving it around for 20 min. probably didn't really charge it fully (I seem to recall seeing somewhere that it takes 20 min or so driving, just to "replenish" the charge used to start the car). You could have a bad battery , or you may just need to fully recharge it. I would suggest taking it to a place like Autozone, where they will test (and I think) charge the battery for free, if you don't own a charger. FWIW, I periodically put my car batteries on a charger just to make sure that they are "topped-off" once in a while (I'm still on my original 06 battery - knock on wood).

I agree with Andrew above. From what you've said, can't tell if battery is bad (dead cell maybe) or just needs more charging, so have it checked. I also agree that 20 minutes of driving was probably not enough to fully recharge your battery in that case. While I also use miles driven as a rough "measure" of battery charging, what really counts is time spent at a certain charging rate, whether that's from driving or from a charger.

Once when I went on a trip for a week, came back and car was dead...sitting in garage... Porsche Roadside guys and the dealer both said that up to 08...due to background use of electronic systems that batteries can die...apparently from 09 on they have less power drain when shut off...

My 2008 Cayman S has regularly sat in my garage for a week or more with no issues starting back up. I suspect most cases of a battery dying after a few weeks of being parked involve a battery that was failing to begin with.

If your car is going to be sitting for 2 weeks or more, put a battery tender on it. If the alarm is armed, it may completely discharge even faster. And, trappedatuf, I think you're probably getting very near the end of your battery 's life. IMHO- When batteries go bad, they do it fast. You get a couple notices of slow cranks, then kablammo- no crank, no charge.