One of the things that's always bugged me about my car is the speed in which the battery goes flat

I've heard lots of stories from various sources, all seem to say it's a pretty common thing with Porsches

Since I won't be satisfied/convinced that my battery drainage is 'normal' until it's been tested - Can somebody give me instructions on how to test for battery drain?


I've recently remembered that my car has a GPS tracker device fitted (incase it ever got stolen) and I've heard they can have quite an impact on battery drain - Is there any truth in this?

And other than taking the car to the Manufacturer, How would I go about tracing where in the car my tracker device has been fitted?

 

Alot of time if your car sits for a long time the motion sensor inside the car will stay active for a week or so and only turns off to conserve the battery. You can avoid this by quickly pressing the door lock button on the remote twice. You will get a light flash and horn honk to verify its in effect.
Sorry I don't know about gps placement. But this step will increase battery life if you don't drive it often.

 

Thanks
I'll look into it

(just reading your GT2 clutch DIY)

 

you are going to need a good voltmeter w/ an amp meter that has at least a 10 amp setting which should have user instructions on how to hook it up to perf. amp test ( in series neg cable to neg batt post).Once hooked up properly,you should see some amperage activity on the meter & make sure you have most elec. accessories off(door closed,key out) too high a load will blow the voltmeters internal fuse.Let the cars computors cycle down into "sleep" mode,turn off the int motion sensor w/ dbl lock sequence,approx 5min.Once in sleep mode you will see a constant figure on the voltmeter.That will be your key off draw measurement.General accepted figures for most cars is below .9 amps.If above you can track down which circuit by disconnecting the neg cable to voltmeter,pull interior lamp fuse so you can keep drivers door open,reconnect voltmeter amp setup procedure & start pulling fuses & or disconnecting elec. items while watching for the sleep figure to drop.A wiring diagram is almost manditory for finding the culprit sometimes.There are other ways to track key off draws,but this seems the easiest for most people.Yes our cars do have above avg. key off draw,so dbl. lock & trickle/maintainers are rec. for long periods(3-4 days) of non use.Also remember batteries can be bad & still accept a chg,w/ the true test being a proper batt. load test.Your GPS has to be wired in somewhere & prob under the dash or console

 

The simplest way would be to read the voltage of the battery day after day at the same time, with a multimeter. But then you would need another 996tt to compare it to doing the same thing.

Anyway I would recommend the cigarette lighter trickle charger (Porsche makes one), it maintains the battery if you don't drive the car at least a few times a week.
I use it: http://www.amazon.com/Porsche-Dual-Battery-Maintainer-Charger/dp/B001684YCK/ref=sr_1_1?ie=UTF8&qid=1324654760&sr=8-1

 

You're kidding right ????

 

I'm sure he is. Mine lasts about three weeks "if" I forget to turn off the interior motion sensor.
My battery is about 2 years old. Just a cheapy interstate brand.
But the "Porsche" labeled charger in his post is just a rebranded ctek charger. And they are awesome. I love mine.

 

No the charger is recommended

Those GPS tracking devices are constantly on so they will contribute to the drainage.
By the way how long does your battery last when the car is sitting, ant_8u?

 

Would like to add the current draw should be around 10 milliamps which is .01 on the multimeter. Aftermarket electronics would not be unheard of to bring things up to 20-30 milliamps depending which would be .02 to .03. Under no circumstances should it be .9 which is nearly an amp. That reading would kill in 24 to 48 hours depending on the condition of your battery. When doing a current draw test always latch the hood with a screwdriver to turn off the light and close all doors and engine bay. By having the battery mounted under hood tha the engine/starter so far away will cause a voltage drop more severe than a conventional setup with the battery next the the engine.... so when voltage goes down the amperage requirment will go up causing the need for more reserve cranking amps required which often gives us that click click click but no start on a sub par battery. If you go through some of my older post you will come across a detailed currend draw test procedure........good luck and Merry Christmas

 

Yes ideally should be under .09 amps-forgot to put in the zero,but I've seen some diff car makes with much higher,some in the .09-.10 range-not on a 996tt though

 

Thanks to everyone that's replied so far
I'll pick up a voltmeter next week and see what I can find

What is it about the Porsche electrical system which causes the battery to go flat?

Other cars I've had could be left for months at a time, but I doubt I could do that with the Porsche even without a battery drain

 

have had collector cars in the past and alway had a dead batt and it was always the one or two in the front of my storage area so i could not get the one out out that i wanted to drive... got a trickle charge and all was well.... now all i have is the porsche which i drive about once a month and yep the batt is always dead, just recharge that baby the day before i drive it