What is normal battery current for a parked 997.1? My clamp meter reads 200 mA, maybe less when the car is locked. (I removed the trunk light bulb--it always drains the battery if the hood is inadvertently popped.) Just unlocking it brings it up to an amp and a half or so. I know it's enough to drain the battery without a trickle charger after a couple of weeks. But what is normal drain if it's sitting in my garage?

I have a 6-CD changer that wakes up and hums for a while if the battery is reconnected. I assume there are other idle currents as well...

 

How old is your battery? Maybe its time for a new one

 

My battery drained when the car was not driven just for around two weeks back in Jan. battery was completely a goner and had to be replaced.

..my 1999 Lexus LS ( yes 1999 ) left not driven after 1 + mos always starts!

Go figure, got myself a trickle charger now.

 

Right. Been there, done that. The dealer will tell you that you NEED to drive at least 25 miles a day to keep the battery charged.

I drive about 12 miles a day. Probably the most fantastic drive to work imaginable, right out of a Porsche ad. But I digress. My car is designed so as to drain my battery without a trickle charger. Who engineers something like that?

If a battery is chronically near discharge its plates will get sulfates deposits, increase the internal resistance, reducing battery life. I know that...

But what is a "normal" amount of current drain when it's just parked, sitting there? How much is too much?

 

This subject came up the other day for reasons I won't go into and a Porsche tech told me he likes to see under 100mA and 50mA or even 25mA is better. I didn't have a chance to ask him why the difference but it may be due to different options that have a different parasitic draw.

The clamp on meter may not be giving you a good number. They can be hard to zero. Connecting a meter in series is better.

Be aware that when you unlock the car lots of things wake up. Some controllers/gateways come alive and message traffic on the Can bus just flies over the wires.

If you wake up the engine controller the load can go up to scary levels. A 2008 BMW 330XI registered 9 amps when the car was unlocked and the passenger driver's door opened.

In my 03 Turbo when I unlock the car the car's memory seats and heater and such adjust if these were changed before I shut off the car the night before. I have not measured the electrical load in this case.

Even when you lock the car it can take 3 minutes (by my watch) before the ECU and other high electrical load items power down.

If you do not lock the car things may remain powered up even longer.

You have to connect the meter and be sure the trunk compartment light is out -- I remove the light housing from the trunk -- it just pulls out -- and then unplug the light (LED?) bulb. Then wait. We used a logging meter the other day to capture minutes of readings. Has a Blue Tooth feature too so one can pull the data out of the meter without disconnecting it...

 

While computers are the cause of battery drain in modern cars, it's interesting that a Porsche can drain a battery in a couple weeks while my new Jag, with an equal number of computer controlled options, can sit for a month with no perceptible battery dain at all. My 2006 GMC truck sits for the winter months and still starts though it admitedly is pretty basic in design and has a limited option count. Only the Porsche has to be on a charger. Would love to know why this issue is problematic for Porsche
.

 

How about a battery maintainer or charger. I picked up a CTEK (I think) off amazon with the adaptor for the cig plug.

Works great

 

Unless your battery is in really poor condition the luggage compartment light should not drain the battery especially since it will shut off in about 2 hours - "Load Switch-Off info from the Owner's Manual

If the ignition key is removed, loads which are switched on or are in standby mode (such as the luggage compartment light, interior light and radio) are automatically switched off after approx. 2 hours.

 

Thanks all--yes, the clamp meter is tricky to zero--and about 3 or 4 minutes after locking the car (with the hood open--and the trunk light bulb removed) it looks like the current draw is less than 100 mA. Yes, at this point I could put an inline meter to see how low, but below 100 mA it's probably not important, and if the jumpers jiggle, the current surge at reconnection would blow the fuse in the meter. Already done that.

Does the trunk lamp really turn off after 2 hours? Do I need to select that feature, or is it a default?

In any case, I still don't drive enough per day to keep it charged as recommended. I suppose that's the price I pay for having a short commute.

 

The "Load Switch Off" feature is automatic - nothing to select. Another feature - if you open the hood and then arm the car, the light will go out in about 20 minutes - same for the engine compartment light

 

I also have the CTEK, I hook it up once every week or 2, one weekend I do my Shelby, the next I do my 911. It seems to take about a 12 hours to get it to full each time.

I do it through the moonroof with the Cigarette Lighter hook up.

 

i think battery maintainer is a must for porsche cars
the original one is very expensive in comparing to aftermarket ones
i used one from & it works fine
its almost as this one here
http://www.batteryweb.com/12106A8V-batteryminder.htm

 

Use a battery maintainer. I use mine anytime I am working on my car and its out if commission for longer than a week. Plugs in to cigarette lighter. I close the door right on the cord and lock the doors with no problems or damage to the cord.

 

That would be a great question for Porsche to answer....it seems that this is their Achilles heel.

 

When you lock your car via remote, the alarm is armed which is a constant draw.
There's a radar sensor as well on the interior of the car that is always monitoring when armed.
Also, apparently, either the car is always communicating to the remote or running an internal timer.
This is why after seven days, it locks out the remote and you have to insert the key to reinitialize.
If you have a secure garage and are comfortable with not locking the car as I am, then the car will not forget the remote and the battery drains at a much slower rate.
Still, having said that, I always plug in the battery tender anyway. I replaced my OEM battery this past summer and it was an original from 2005!
The average car will last about a month or so before the battery goes flat if it's not charged so it's really not that unusual.