Battery keeps draining in Porsche Boxster

I recently purchased a 1 year old Boxster with 12,000 miles. It is fortunately still under warranty. Roughly every 3 weeks the battery completely drains. After it is jump started, the dealership can not find anything wrong. They have replaced the battery, and the same thing happens. No faults on the computer are tripped and under monitoring at the dealership, the battery does not drain. It seems to be an intermittent problem. The dealership has checked “all the systems” including the starter, and can not find anything wrong.

It would be nice to know how much current drain there is on the battery while it is parked and things have gone into the sleep mode. I assume the shop has checked that along with the charging system and found nothing out of the ordinary. There could possibly be something like a faulty door switch that is causing things to turn on when they shouldn’t be. If the dealer can’t help you any further with this issue then you are most likely going to need to find a shop that specializes in electrical faults. They should have the test gear and expertise needed to find the problem. There might be a problem getting the service done under warranty though unless the shop can do warranty work.

You may find this helpful.

If it has an alarm system, that would be a prime suspect…

Am aftermarket radio sustem inocrrectly installed can also drain a battery.

A mechanic can find which fuse circuit is causing the drain by following Barkydog’s procedure posted above. Once he finds which fuse circuit is causing the drain, it’s not difficult to track down the exact culprit, e.g. alarm system, radio, whatever.

Not the first time someone has experienced this, the door switch could be sticking or something like the glovebox/trunk lights could be staying on. How often are you driving the vehicle? You might consider buying a trickle charger.

So I got the car back from the dealer and they’ve solved the problem (not). Porsche/ the dealer claims the car was not driven enough. Even though we drive the car at least every 2-3 days for at least every 15 minutes at a time, that apparently is not enough to maintain the charge ( so they claim - why they are just telling us about this now and not when we purchased the car or after the first 2 times we brought it in is beyond me). They even pointed out in the owners manual that if the car is not driven for prolonged periods then the battery should be charged at least every 6 weeks. Apparently Porsche’s/the dealer’s definition of a “prolonged period” is now 2-3 days, and yes I have this in writing. Either Porsche/ the dealer is blowing smoke, or we need to get the word out to all Porsche owners that not driving your car for 2-3 days is now considered a “prolonged period” and virtually all Porsche’s need to be hooked up to trickle charges.
I’ve already got an appointment with another repair shop. Fortunately it is still under warranty.


It seems like the dealer can’t get a handle on the problem

It also seems like they’re feeding you a line of BS

It seems like it’s time to go to another, hopefully friendlier and more competent, Porsche dealer

Good luck and please keep us in the loop

A new battery should not be running down in 2 or 3 days so they’re blowing smoke.

First thing to do is find out what kind of current draw (in milliamperes) is present when the vehicle is at rest.

Somebody is smokin’ sump’n if the dealer is telling you 2 days is all the battery supply can take on a good fully charged battery. You need a shop that has some test gear that can show historical data on the current draw of the battery. It seems like the real problem is happening after the car has been parked for a while and the shop hasn’t been able to pin it down.

My neighbor was told the same story by the Porsche dealer in Northern California. He was also told that if he didn’t drive more than 4000 miles a year, the battery warranty would be void. If you look at the warranty, it says “This warranty does not cover: 2. Batteries damaged from storage, lack of normal vehicle use, or non Porsche approved electrical or accessory installation.”

It also says that it is your responsibility to understand that the car is meant:

• To be driven on reasonable road surfaces within legal speed limits.
Porsche Guidelines specify reasonable mileage to be at least 15
miles / 24 kilometers per day or 6000 miles / 9600 kilometers per
rolling 12 months.

It also says:

(Note: A battery maintainer is available at your local authorized
Porsche dealer. It must be used to maintain your vehicle’s battery
state of charge if your vehicle will not be used for several days.)

Maybe you or I think this is bogus, but there it is.

I would like to know what the normal current draw is supposed to be for this car while the car is parked.

how ofen do you drive the boxer? if it sits for days at a time by a battery tender for it

Maybe the battery isn’t getting charged when you’re driving around. There might be enough voltage to keep the alt warning light off, but not enough to recharge the battery.

Sounds like Porsche is covering their worthless ass

I’ve never read that in ANY owner’s manua

I just can’t buy into the part about allowing a Porsche to sit more than a few days and the ensuing dead battery being considered normal. A number of Porsche owners state they allow their cars to sit for weeks and there’s no problem.

The parasitic current draw needs to be known and near as I can find; approx. 30 Milliamperes is what it should be. Get into a 100 or more and there likely will be a problem.
There are also several references to others having similar problems and the cause was some widget tied into the ignition switch barrel.
Not being a Porsche guy I do not know what this widget would be.

Offhand, it sounds like something is not going to sleep as it should.

In any case, OP’s worthless dealer is referring to the owner’s manual BECAUSE they can’t, or don’t want to, get a handle on the problem.

Time to find someone willing and able to solve the problem.

I agree with @ok4450 . . . it sounds like some module isn’t going to sleep, or perhaps it’s waking up and killing the battery

Since everyone is asking, the dealer found no draw on the battery, but I have no confidence in this dealer. Since taking ownership, we have been averaging 500 miles per month, within the guidelines. I checked the records of Boxsters on sale in the area and the typical Boxster driver averages 380 miles per month. Again, that should mean that most Boxster drivers should be experiencing similar problems, or there is something seriously wrong with this car.
We’ll see what the other dealer in town says later this week.

Please try to find out what the current draw is on your vehicle and let us know what that is. Normal current draw for most cars is around 25 milliamps. This keeps memories alive in things like the engine ECU, radio, and other modules. There has to be some current draw on the battery so I’m not sure why the dealer stated they couldn’t find any draw on the battery.

I suppose the problem you are having could be due to a different problem that could make it look like the battery was discharged. If there is a bad connection in the primary distribution panel, say to the ignition switch, this would make it look like the battery is dead but it really isn’t. Power is getting cut off before the switch. This may be what is really happening unless someone has actually checked the battery voltage and verified the battery is drained.

Perhaps the mechanic blew the fuse on his DMM

I’ll admit that I’ve done it.

There have been cases where I didn’t measure any parasitic draw because the fuse was blown

Nobody’s perfect