enzom

All - I was curious to find out how long you think the car can sit in the garage before I need to worry about the battery. I guess I can always just hook it up to the battery tender every time I park the car for the night, but when I feel that I will be driving the car again in "a day or so", I just let it sit. What I'm wondering is what happens if a day or so becomes a week. Has anyone noticed difficulty starting the car if it has sat for a week? Two weeks?

Thanks.

ruhlich

When I know the car will be setting for at least a week, I connect a Tender. For up to three days, not a big deal.

I have discovered that my past BMW motorbikes have short-lived batteries, even if kept on a Tender. So, I bought an Argus BB-SBM12-PS battery Bug and installed it permanently on my bike. It continually monitors voltage and %capacity that is left. (Available on Amazon...$50). (Note: The battery can indicate over 13V and still only have 1/2 or less of its new capacity left. My bike's battery now shows 58% capacity and 13.8V and I've kept a Tender on it 100% of the time when it's parked.)

You could attach one to your 991 battery and tie-wrap the monitor (about 1" x 1") to the frunk liner grill. The downside is having to open the frunk to inspect the readout.........unless you run the leads (monitor) into the cabin someplace (about 36" leads).

Otherwise, it's pretty much a guess from anybody as to a safe life length of time. But keep in mind that even though the car sits for a time but the battery has retained enough voltage to start it, that it can lose capacity that can't be regained even with an auxiliary charger.

Thus, the battery monitor.

BradB

If over a week I put my cars on life support. I use CTEK's.

John's 991

I do about the same as ruhlich. I keep a tender connected if I won't be driving the car for a week but three weeks should be ok. The tender I use connects to the positive terminal on the battery and ground post in the "frunk" to the right of the battery.

It takes less than a minute to connect and I like knowing I have a fully charged battery so use it very regularly.

Team Plutonium

Same here.

ricm

After a week or so; sooner in cold temps.

1analguy

Not to highjack the thread, but I've seen this same statement more than once. I sold my '07 BMW R1200RT last fall, with only 13,000 miles on it, because I was no longer using it enough to justify owning it. When I first got it, I got a gel-cell Battery Tender for it that I kept on it whenever I wasn't riding it. The day I sold it, it still had the original battery in it and it still started like brand new. You did know that many BMWs have gel-cell batteries, right?

VIC_50th

Same as BradB - use a CTEK.
I went through two batteries in 3-4 years with my 997 - driving the car anywhere from every day to every week-10 days. I would normally only use the CTEK when the car sat for a couple of weeks or more.
After the second battery died, I mounted the CTEK on the garage wall next to the driver's window, plugged it in to the cigarette lighter every time I parked - never another problem.
If I were you, leaving your car for >3 days I would certainly use a CTEK or similar.

CTEK supplies the Porsche branded battery maintainer - identical in appearance (except the logo, of course).

LexVan

I use the old style Porsche battery maintainer. Center console (smoker's package) cig plug. Close door on cord. Simple. I plug in whenever parked in the garage. I can easily get +6 years on a Porsche OE battery.

Slantnose!

Like they said, probably a week...but it'll last about a month or so fine.

rpilot

mmm.. what makes a Porsche different from say a Honda, whose batteries I have left for over a month before without any starting problems. Or my old BMW whose batteries were regularly left for 2 weeks or so. I ask because I am curious.

I have never had to leave my C2 for more than 8-9 days and it has started fine so far without any problems without a tender. I will soon be moving into a highrise condominium building without access ? to a plug in the parking garage soon and my business travel is going to increase to the point where I may regularly be away for 2+ weeks. Am I going to come back to a dead car every time ?

MerlinsGarage

If the battery is completely dead, to access the (electrically controlled) frunk you need to connect a 12v source to the "rescue" terminals next to the fuse panel.......drivers side left kick panel.
30 year old Honda.........well you know, "PULL".
Porsche HAS to correct this issue, and have a retrofit for prior models. Flip up/over hood emblem and lock!
IMHO of course.

kosmo

1 week or so.

robsc2s

+1

willyspub

I had the same problem years ago with my 996 C4S. Parking ramp in my condo had no plug, and it wasn't my DD so I might go a few weeks.

The fact that I needed to jump my way into my own hood to get to the dead battery was unbelievable. What's even more unbelievable is that they haven't remedied this oversight two full redesigns later. How is there not an analog hood pull when the battery is dead? Crazy. I mean, there is an emergency cable (at least there was on the 996), but it was not really accessible.

To remedy it, I would actually unplug my battery if I knew it would be sitting for a while, then bring a little portable charger thing next time to jump the fusebox to get back in. Annoying to do that and to need to reset the clock, but better than buying yet another new battery. And adds a level of defense from thievery. Although, you'll need to reconnect the battery each time you open the door before you repeat the trick, because otherwise the window won't retract slightly and you won't get a good seal on the jam (or possibly even shut the door).

As for the question about what makes Porsches different, I don't have an answer other than that it seems like their passive systems require (much) more juice than other cars. Although I believe Porsches and batteries have been getting along like dogs and cats since before there were tons of on-board computers, so who knows.

What I do know is: leave virtually any other mfr alone for a month, and it would be shocking if it didn't start; leave a Porsche alone for a month, and it would be shocking if it did.