How long is normal for Boxster to sit & battery still work?
 

I did some searching and found some battery related, but nothing that's really a match for the question.

Being... I sometimes am away for business for a few weeks at a time and when I get back the battery has enough power to turn on the interior lights and warning lights but won't even attempt to crank the engine. I end up having to jumper cable it.

I used to own an RX-7 and sometimes that car would sit for months with no issue at all, but the Boxster is behaving nowhere like that.

Anyone find this an excessively short amount of time for the battery to be drained? And if this isn't the norm, then any thoughts on the matter?

My car hasn't sat for longer than a week, but has been close to that and I've never had an issue. But it seems many owners keep their cars on maintainers or chargers all the time unless dd. Seems as though the box has a high battery drain rate, but maybe someone can fill us in on what it is that is draining it? How is it different than other cars out there?

I have left my Boxster for 2-3 weeks a few times with no issues. It probably has more to do with the battery than the car.

If it were me, I'd pull the battery and take it to a shop and have it tested (unless you can do it yourself). A good battery fully charged at rest measures at 12.5 volts. A bad battery at full charge at rest no load is at 12 volts. A good alternator attached to a good battery measures 13.2 volts to 14 volts with the engine running.

Secondly, storage temp in cold weather can also contribute to decline as well as state of charge when initially stored, eg., was it subjected to short stop-&-go before shut down?

Lastly, buy one of these and use it, I've been using them for years, they work great:

Amazon.com: Battery Tender 021-0123 Battery Tender Junior 12V Battery Charger: Automotive

This may seem dumb but are you leaving it unlocked? I have an after market alarm on mine (not by choice) and it seems like leaving it unlocked makes the alarm system drain the battery waiting for locking input. When I lock it there's less issue. Just a thought.

I previously had a Interstate battery. It would start the car after a 1 month storage. But that's probably the longest it has ever sat with out being run. I usually pull it out of the garage warm it up and take it around the neighborhood if the roads are dry through the winter. New this winter is an AGM PC925 Odyssey battery so time will tell.

I had an Interstate, I was not able to find one locally when mine died after 7+ years. Easily one of the best batteries you can get for the 986.

If the battery is more than 5 yrs old, replace it. These cars do have a small parasitic battery drain while at rest especially if left unlocked. If you leave the car unused for several weeks often, put it on a maintainer or add a battery disconnect switch.

Another thing that can kill a battery is a sticky switch on trunk lamps. Both my front and rear trunk switches got fluky over the years so I just pulled the trunk lamps and that solved the battery drain problem. If your car has a glove box lamp, it too can stick closed and kill the battery.

All great leads. Thanks everyone. Keep them coming.

I always lock the car even when in the garage where it is kept.
Given I don't know the history of the battery as I just bought the car recently I will check that as the first possible weak link. The guy I did buy it from did have the front trunk bulb disconnected though and said he had on a trickle charger for storage, but I'm thinking maybe I didn't get the whole story and it was more that he always had it charging because of some sort of parasitic drain. Maybe I'm wrong though.

Either way, some of the cross section of replies gives me an idea of how everyone else is shaping up on this issue.

Thanks again

I often leave mine for a month or more when I'm out of town. I disconnect the negative terminal from the battery (no issues with the computer) and I remove the frunk catch from the frunk (2 bolts) so it can't lock. Since I got an AGM battery, I don't bother with a trickle charger anymore.

Although I agree the Boxster might cause more drain on the battery while not in use than our other vehicles, for most its also the vehicle that might sit unused longer.
In my case the Box is my daily driver in the summer, and my Canyon ends up parked for weeks at a time and with a very low or dead battery if I forget to take it for a drive at least every 2weeks, its a 2012 and the battery never gives me trouble when used regularly. My Boxster will go on the Battery Tender if I don't use it more than a week.

Curious....why would locking the car use less power than leaving it unlocked? Locking it activates the alarm, which causes drain. Unlocked....what's draining then? I always leave my car unlocked in the garage to save the battery from the alarm and constant flashing alarm light.

Ditto. I thought the same. I always leave mine unlocked and I had it die a couple times initially but since getting a new battery and subsequently a new alternator, not once has it died after having sat for over a month unlocked.

I wonder if the lock/unlock question mentioned above has anything to do with the remote lock deactivating after 7 days. (i.e. - After 7 days you have to open the door with the key, the remote unlock will not work.) That battery savings by locking the car could be significant over time, versus leaving it unlocked.

3 years/old BOSCH battery 80amp (I think) and its already starting to flat out on us. If I haven't rolled the boxster for let's say 4~6 weeks, it revs clicks only. Needs a quick 15min charge and ON it goes!

Got an (ultra)slow leak in the front-left tire. That goes down to 20psi every 4~6 weeks as well lol

Sings of failing IMS? Need a new car right?

A good question. I don't remember the "why" but only that several Porsche factory guys have suggested this. Perhaps the DME goes fully to sleep when locked. Easy enough to test if you can connect an ammeter and measure current draw before and after locking. Running long leads out from under the hood should work.