Alfaguy2

Is it normal for a 911 to drain its battery so quickly? I think its quite common on 997's?
I went out to my 997 this morning after not having used it for about a month and the battery was dead - again.

I bought a new battery last year thinking it might be a faulty battery but it drained it in the same manner so now I alternate the two batteries - and always leave the bonnet (hood) lid open so that I can get to the battery if it goes flat.
Could it be that the interior light is on under the bonnet as a result of leaving it open?

I always lock the car when its garaged so it goes into sleep mode if not used often but that does not seem to help much.

No HTwo O

Yes that is common.
Yes it could be the frunk light.
By a Porsche (or C-Tek) battery maintainer. If not being driven, it should be plugged in.

user 72902

I use a Battery Tender to keep my battery charged because my 993's got schizophrenic and did weird things when the batteries were weak. I do not close my trunk lid all the way but close it to the point where the latch catches. The trunk light goes out after a few minutes and I can still activate the alarm; it is easy enough to see if your P lights are off by going into the garage when its dark.

Menmojo

It's normal.
997's are known for this issue.
Get a battery tender.
If I don't plan on driving it for a couple days it's plugged in.

AllForTheCash

Normal as well, Happens after a weeks of non-use.

irish guitar

Alfa, as I travel so much, my '06 Carrera S sits for up to 6 weeks at a time in the garage plugged into a Porsche battery tender. Happy to report that after 30K miles it's still on the original battery and never once has it had an issue starting.

Hope this helps.

Minok

I think if you drive the car once every 2 weeks for at least 30-40 mins, you are probably fine. Once you go beyond 3 weeks of sitting, a battery maintainer makes sense.

chinole

Also true on the 996. So battery tender is well worth it if you don't drive enough...

Mumbles

If you'd like to pass over the keys, I know of a few friends that'll be more than happy to keep her warm !

19VFB19

Fell victim to this today....haven't driven the car much at all (stupid rain), and today wouldn't start.
I do have a battery tender hooked up direct to the battery now, need to buy the cig lighter adapter.

Odd that the battery (new Porsche battery installed by the Dealer as part of the CPO), is dead already. I will keep the tender plugged in when the car is going to sit for more than a few days.....

I need to drive the car more.......

Topwind

I recently was told by service mgr at Porsche dealership that if the car isn't driven at least once/week, you're at risk for draining the battery (especially with an older battery). As others have said on this thread, get a battery tender.

Lance-AR

I was told 500 miles a month or use the tender.

gabe2006

It's normal. If I don't drive it for roughly 30-40min every week it cranks really slow and may throw a 'PSM in diagnostic mode" message if the battery is really weak. Drive it more often or buy a trickle charger.

tigerspill

If the battery does go flat, is it just a matter of charging it again? Or is there any special procedure required?
Also, If it does go flat, does the alarm start sounding?

Macster

Lead/acid batteries do not like to be fully discharged. While you might be able to recharge the battery enough that it will start the engine the battery will never be what it was before it ran down.

If the battery is new or nearly new it might have enough margin to give you some more life but it could let you down again, almost certainly will let you down again at some point the future.

Thus I would bite the bullet and replace the battery then take whatever steps are necessary to keep the battery fully charged. If one can't drive the car every week or so and run the engine half an hour to top off the battery to replace what it lost over time and then at engine start some kind of battery maintainer is called for.

BTW, if one leaves the front trunk open this can have the interior light on which can drain the battery very quickly. At the dealer in the service bay while almost every car has its front trunk open the tech disconnects/unplugs the interior light so this doesn't discharge the battery.

There is a front trunk lid emergency cable release and what one can do is have the tech find this and reroute it so you can use this to open the trunk in the event the battery dies.

Or you can connect 12V power to the special post in the fuse box and then connect the 12V power source ground to the door latch. This supplies enough power for the front trunk latch to work. It will not recharge the battery or supply enough power to start the engine. Do not turn on the key if you use this technique to effect an emergency opening of the trunk.