JasonNY

Have a '12 997S Cab that i drive fairly regularly. Didn't drive for a few days and last night battery was dead. Checked and no inside lights or anything was left on. I bought the car over the winter and had it on a trickle/battery tender until April, so it was fully charged then.

I have a battery/alternator/starter-motor tester that when the car wouldn't start said "weak" which according to the instructions means "ok" but needs to be charged. After a jump start the load test (picture shown) says battery is good. I trickle charged the battery overnight and it still didn't finish charging so it was pretty run down. Tested the charging system (alternator) and put it through it's paces, AC on, heated seats, lights, ventilated seats, put the top up/down a few times, and can't get any tests to fail. So the question is why the heck did the battery die? I'm more concerned about a problem with the electrical system in the car. Shouldn't be going dead, especially in warm weather. Any known issues to ask the dealer about?

kosmo

what was the voltage w/ the engine running? it s/b about 14.

Lastly the cable b/w the battery and alternator is known to go bad.

JasonNY

Yep, it was 14v, right in the green ok box above "charging system".

Thanks for the info on the cable, i'll definitely mention that to the dealer.

JasonNY

Ok, so I just spoke with my service advisor at my dealer. I told him everything is checking out, alternator to battery, and he says if you leave the car unlocked like I did for several days these Porsches' electronics will drain the battery. He says to lock the car whenever im going to leave it for longer than a day to avoid battery drain as it shuts off power draining modules when locked. I've never had this happen with any other make of car but he claims it's a Porsche 'issue'. Can anyone comment on that?

G356

Dayum...didn't know that. Just had a battery replaced under warranty n dealer never mentioned this.

BIG smoke

Did you buy the car new?
If you bought it used, could it have a LowJack in it.
Had a few friends with LowJack/Boomerang systems that would drain the battery over a few weeks.

jhbrennan

Yes that could happen but usually only if you have a very weak battery to begin with and the period of time is lengthy - I don't think several days is lengthy. Since it looks like everything has checked out, maybe you just have a bad battery - won't hold a charge.

JasonNY

Possibly, but the load tester I'm using should spot a bad battery. The needle would show as bad or the needle would be slowly moving down when the load is subjected. All that said I can't say if these things are 100% accurate. I'll keep a close eye on it, and replace it if it looks to not hold strong.

fskof

The cable b/w the battery and alternator is known to go bad on the 997.1. It was changed for the 997.2 so that is not the problem. My first question is do you have any after market items installed like radar detector, Ipod,Sat radio that could have drained the battery?

JasonNY

Only an Escort 8500 hardwired to the rearview mirror dimmer, but that shuts off with the ignition. Nothing else installed, and no left on interior lights.

fskof

Good.. now we know that is not the problem.
When you do drive the car do you take it on short drives or do you go on longer drives where you can get the revs up. These cars dont like the short stop and go drives. Its possible the battery never had a chance to charge fully and it died. I have seen this happen to my friend who lives down town and only goes on short 5 min drives in stop and go traffic. The battery never had a chance to charge and it died after 1 year.

JasonNY

It's a mix, say for every two short drives there is one longer one (45min+). I believe the last drive I took before it wouldnt start was a longer one. One thing I did do, and I try not to do was shut the convertible top without the engine running. I'd imagine that'll burn a few amps to do. Usually I open/close when the car is running, but I remember I left the top down didn't use the car again that day so closed it off the battery power.

fskof

Sounds like you are doing everything right. What I would do is to try to repeat the problem. Park the car for a few days and then go try to start it and see if the battery is dead again. You might have a weak battery. I have never heard of a battery drain issue with the 997 that didnt have some sort of after market item installed.
Many here will keep a battery tender plugged into the car when the car is parked but I only do that if I know the car will be sitting for more then 2 weeks. I have never had a problem.

Let us know what happens...

stronbl

I have kept mine off a battery tender for a couple weeks at a time, but with doors locked. No problems other than cannot unlock with remote (normal). But car starts fine and battery recharges to full quickly.

I would test the locked doors part first and see if you have a full battery and can start the car; if it works as your service manager says, then test it again with doors unlocked. If you get the dead (drained) battery from the unlocked, then you know there is something to the door locking claim. I know the 991 has a battery protection mode that gets triggered under some conditions, perhaps it is a learned change from the 997.

USMC_DS1

I leave my car on the trickle charger. It's an inexpensive and convenient $100 investment compared to all the complexity of trying to open up a drained car. FWIW, if you don't lock the car it should shut down all non-essential electronics after a few hours. One thing I've been mindful off in our TX heat is the fact that my engine fan will kick in after I park the car. This will drain my battery a bit so I've gone to a policy of just plugging her into the trickle charger every time she's parked in the home garage.