good tip.. will verify that

 

There is always drain, as long as the battery is wired to the car. There are sysems that are permanent consumers. Normal siting drain is about 40-45mA. As stated above that reduces battery capacity by about 1Ah per day.

 

Actually, a simpler trick to awaken a long standing 997 is to just pull up the door handle first. Then click the open door on the key fob. The door unlocks so you now open.

 

Yes, these cars use battery power when shut down. I don't know where the drain comes from. No lights or anything else on. How old is your battery? I've had the same thing as you describe happening twice with older batteries. Quick and unproblematic starts one day. Next day the click so no warning at all of a battery on its last leg. In both cases it went from what felt like 100% healthy batteries to dead from one day to the next. So in one way, consider yourself lucky getting warnings that something isn't right.

With a good battery and alternator you should be able to leave it sitting for two weeks, maybe even three. I've done it with newer batteries. But with a battery two or three years old, I just disconnect it instead of messing with a tender if I'm going on a trip two weeks or longer. Cranks like a champ when I reconnect the battery even after sitting for three weeks or longer.

Why am I doing this instead of using a tender? Because I had a tender once that failed. Disconnecting the battery has been fail proof for me so far. As long as you put an old towel or whatever over the frunk locking mechanism. Close and lock the frunk after you disconnect the battery and you'll have problems since unlocking the frunk to reconnect the battery requires battery power.

 

thank you for this suggestion of CTEK. I just ordered the 5.0 with the cig adapter. I think I might replace the battery and the alternator anyway but this smart trickle charger will be helpful in any case.

 

Good advice about the frunk towel and battery disconnect, but there is also a battery connector behind the fuse box panel where you can connect up and open the frunk. this is normally used to maintain settings when changing out a battery.

 

Gonna keep an eye on this thread as I've stepped into a dead car twice in 2 weeks. Last time it was actually the driver's door bulb that came loose.

So far I've taken the battery and had it tested and was good. I also checked battery voltage after being disconnected for 5 hours (12.7V). Amperage draw in park is 30-40 mA. Alternator charge is 14V+ on idle.

So it seems like generally systems are working.

I'm starting to wonder if leaving it unlocked really was the culprit.

 

Bought a CTEK. I leave it plugged in. I have a 12V cig adapter but ended up screwing in a more permanent battery terminal adapter and leave the end dangling above the battery compartment. no more question about the car starting regardless of how long it sits in the garage. The model I bought for my Cayman is 40-206 MXS 5.0.

 

There is a table in the workshop manual that explains how to perform measurement of the drain and lists the expected drain per module. The conclusion is: with the maximum of extra features the drain is ~20mA. If you have a ~70Ah battery installed it should last approximately 35/0,02 = 1.750h. 70 days/10 weeks/2+ months to reach 50% of its capacity (slightly below 12,1V) (when starting would be impossible without damaging the cells). I have a 74Ah Varta Battery since November 2016 that still goes strong, but I have it always at the tender when in garage. Am curious how long it will last, but probably I will prophylactically exchange before. Fear.

The only way to trace the drain is to measure it.

 

this is the only car I've ever owned with these ridiculous battery drain problems. If a cheap *** domestic car can sit for 2 months without a battery drain, why is this Porsche issue so widespread? and what's the likelihood that most Porsche owners have a loose wire? If that's all this is? I'm not complaining, I'm just saying I'm not putting up with it, it stays on the tender and I'm not going to troubleshoot electrical. jmpo.

 

Little OT but came homw from 2.5 week vacation Wednesday to 2 dead batteries. One my wife's Mercedes E320 Diesel sedan and 2nd my ML320 Diesel SUV.
Both batteries were dated about the same 6/2017 time period.
I tried charging both but couldn't get them up higher than 11V so bought 2 new Interstate's. ---->Boy Core charges have gone up now $25, I remember $5 years ago.

 

I agree chasing loose/problem wire is a bitch. My current (pardon Pun) 06 997 C4 has no battery drain issue but I keep the CTEK Tender on it all the time while sitting in garage.
Just good practice to keep battery in good shape for longer period of time.

 

Do we really need an ODB tool to reprogram the car if we replace with a non-OEM battery? I've been having problems lately -- the most recent time required a jump start after I'd parked for about 20 minutes. I'm sure it's because the 997.2 has gone from being my daily driver to a "when weather's nice and I can move vehicles around to get it out of the garage" driver. This past winter it spent 3 months in the garage before I tried to take it out and found it wouldn't start. I couldn't even pop the trunk using the fuse panel -- ended up getting the 12V power supply for my Davy Crockett pellet smoker and plugging that into the cigarette lighter for a couple days so I could pop the frunk and put a real charger on it.

I'm looking at the Duracell Ultra Platinum but am leery of doing that if I have to worry about reprogramming the car. Never had to do that when swapping batteries in any previous vehicle but these are getting to be computers on wheels.

 

Never had to reprogram anything in a 997.2 with a non eom battery.

 

^^Same here - No need to re-program after replacing OEM with Interstate Battery.