Dead battery issue

I recently bought a 2004 911 from a used car dealer. When I went to pick up the car they were charging the battery. I was assured that the battery was new. The manager told me that he had owned multiple 996 models and he showed me the trick of leaving the trunk unlatched if I had periods when I wasn�t going to drive it. He told me that periods of non use would result in dead batteries and that this would make it easier to jump or charge. I went away for 6 weeks and as expected the battery was dead. Neither of my other cars had the problem. Is this really a problem that I should expect?

The dealer was likely not being truthful, but 6 weeks is a long time for the car to be inactive. Use a trickle charger when the car is not being used. There are many posts here about how to open a frunk (Front Trunk) when the battery is dead. There is a jump point in your fuse box. Also there is an emergency release cable hidden in the front bumper. Many people reroute the cable for easy access when needed. Leaving the frunk unlatched is likely to cause the light to be on, hastening the battery drain. Have the battery tested at a chain auto parts store. They usually will do it free of charge. (no pun intended).

Test battery voltage. You may have a parasitic draw draining the battery.

Quotes source post: 16377931

Thanks. I unplugged the trunk light before I went away for the 6 weeks to avoid battery drain. Guess the best is to trickle charge. It just seems odd that I can park my other cars for months while we travel but not the Porsche.

They do have parasitic draw, as do many modern cars, as computers, and security systems continue to run even when shut off. A couple of things to consider, first, check your manual. There is a neat little feature on the fuse panel that allows you to jump the hatch opener if battery is dead (so no need to leave it open and disconnect light). Second, apparently draw is less if the car is left locked. Third, these cars can have a battery maintainer connected through the cigarette lighter plug, so no need to open hatch to actually access battery. This makes an easy connection for maintainer use when parked. Last, I would agree with others, I'd have your battery tested. Three weeks to dead seems a little extreme. I've had mine go flat, but it was more like 6+ weeks. I now just connect my maintainer if I know the car will be parked for any extended period.

Dealer was charging the battery, so likely it was drained enough that the car would not start. New or not, car batteries do not last long once they have been drained, recharged, drained and so on. Car batteries are not deep cycle batteries and will last a long time with constant voltage. Thus the need for a trickle charger/maintainer. A brand new battery, car locked so all systems shut down, should last 6 weeks.

Quotes source post: 16378081

No need to unplug the light - the car's load management shuts the light off after 2 hours. Load switch-off after two hours or five days If the ignition key is removed, loads which are switched on or in standby (e.g. power windows, luggage compartment lighting, interior light, radio) are automatically switched off after approximately 2 hours.

You need a battery maintainer (aka float charger, aka battery tender) not a trickle charger for long periods of storage. A maintainer keeps the battery topped up without overcharging; a trickle charger never stops charging, which can damage the battery. You also want to close the frunk and lock the car.

Quotes source post: 16378467

I have a Battery Tender Junior plugged into the cigarette lighter (now 12v socket) but leave the car unlocked. Should it be locked as well?

Quotes source post: 16378718

Doesn't matter when on a tender.

Quotes source post: 16378375

+1 I�ll only add: if you do plan on doing any performance mods for your car, I would get the antigravity battery. It has a feature that all but eliminates a dead battery problem, and saves up to 25lbs or weight or more.

Quotes source post: 16378735

Agreed. Mine is unlocked all winter.

I have a trickle charger in the trunk sitting next to the battery (hidden) tied to the battery terminal with a short extension cord with the end routed next to the wiper and sitting in the area below the window and in front of the back edge of the trunk lid. you don't even see it. it is there all the time. when I am going to be gone more than a week, I use an extension cord to the plug/wall outlet and drape the orange cord over the side mirror so I don't miss it when getting into the car. That way you can lock the car.

You can also route the battery tender wire, when plugged into the cigarette lighter, through the notch in the door weather stripping, which is why the notch exists. The notch is located on the handle side of the door, up a few inches from the very bottom. The door can then close easily and be locked or not as you prefer.

Quotes source post: 16389450

Which door, driver or passenger? I didn�t know a notch existed!

Quotes source post: 16377880

OMG! Classic "used car salesman" shtick! Unbelievable... Anyway, once you have a good battery just make sure you lock the car when you get out (especially if you're not going to be driving it for a few days). If you're going to leave it for a week or more and you want to play it safe, put it on a battery tender. If you don't lock the car it won't go into "sleep mode" and the parasitic drain will be higher... it's not rocket science.

Just a reminder - car locked the systems shut down except for the remote/immobilizer. It continues to "listen" for the remote for five days, then it shuts down and the car needs to be opened with the key in the lock. So make sure your key works to lock/unlock the car, not just the key fob remote. And, as a good practice when everything is working the way it should, pop out the passenger headlight, locate the frunk emergency release cable, and relocate it to just inside the front bumper tow hook plug. Dead battery...just pop the tow hook cover and there is the frunk emergency release cable. Pull it and you're in.

Quotes source post: 16389461

Driver's door for sure, but my recollection is passenger door, too.

so a Porsche engineer was clever enough to design a modification to the door seal but not smart enough to extend the front trunk emergency release wire from behind the headlight cluster into the refueling compartment!

Quotes source posts: 16384488, 16378718

Could you please show a picture of this setup? How do you connect battery tender to a cigarette lighter? Is there a mod for this or adapter? Could you also explain, so as i understand the power from wall socket goes through battery maintainer and cigarette lighter and to the battery? Thank you!

Quotes source post: 16619291

Super straight forward. In fact, if you google Porsche’s own battery maintainer, this is how it is setup. Simply take the leads from a Battery Tender, or any battery maintainer, and replace the battery clamps that are usually on the ends of the leads with a cigarette lighter plug. Many chargers have a pre-made plug you can buy, or you can simply cut off the clamps and install a plug off an old 12V auto appliance, like a GPS or such. https://www.suncoastparts.com/product/CHARGER2.html

Quotes source post: 16619291

never see it and always there setup on my 992. exactly the same on my 996

Ok, I have ordered this cable today, will see how it works. Funny thing, I was just thinking to replace cigarette lighter with USB ports, but looks like I'll be staying with it)) How long does it usually take to fully charge a battery with battery charger maintainer? I have 2A model, it says on it "slow charge" and it's been charging for more than 24hours. I took the battery out for this to make sure there's no drain from the car. PS. I used to have a phone charger cable with wireless charger always connected to the cigarette lighter port. Is it possible that it could drain a battery when the car is off?

1. never clocked the charging. I think the charger has an indicator when charged?? 2. for me, the cord up to the wiper has worked out great - no hassle. always there. 3. they say that device chargers always drain some electrical energy when attached.

Quotes source post: 16621565

thats the thing, it still shows like its charging..

my Deltran battery tender (Costco) says when green light steady, charging is complete (whatever that means) time required to charge: charges at a rate of 3.0 amps/hour so a 15 amp battery should take 4 hours to 80% charge. I'll get a better picture when I get back to mainland and start my 996 which has been on a tender since January 9th

Quotes source post: 16621537

I believe that would be the case. My understanding is that the cigarette lighter is always on. I can confirm this as I use a 12v FM radio Bluetooth adapter that will stay powered on even with the car off for an extended period.

I use this battery charger/maintainer. Works great and easy to just plug in and walk away.

Hi everyone, just wanted to mention some additional options we offer for battery management solutions in our Lithium Automotive Battery and our Battery Tracker module. The Automotive line offers groundbreaking advances by providing a full battery management system along with the first built in wireless jump start feature! You�ll find huge advantages in comparison to traditional lead/acid batteries in regards to weight savings (up to 70%), performance and overall lifespan. Not to mention the built in battery management system which will ensure you�ll get the best out of it. The system basically monitors current conditions and will go into a sleep mode if it detects the threat of overcharge, over discharge, as well as excessive thermal conditions. A button directly on the battery can be pushed to engage the Re-Start feature OR you can use your wireless keyfob and activate it! This is an amazing battery that will provide a great solution so you'll never be left stranded or with a dead battery! In addition to this we all offer our Battery Tracker module for lithium Batteries as well as Lead/Acid options. This device allows you to KNOW the voltage of your vehicle and have that information sent directly to your smart phone via Bluetooth. If you walk within 30 ft of the vehicle the data is sent to the Battery Tracker App you put on your phone. It will also alert you if the voltage is getting low and your battery needs a charge as well as allow you to review your historical data while the vehicle is in storage so you can see how fast your car drains during that time to get an idea of how long you can let it sit before it needs to be put on the charger. Lastly it also has a cranking test and an alternator test...You can track up to 5 devices on your apps so it can work on Automobiles, Motorcycles, RVs or any 12v system to track your batteries health. Very easy to install and use. Please feel free to check out the links and additional info below and let us know if you have any questions. Auto Battery https://antigravitybatteries.com/pro...es/automotive/ Lithium Tracker https://antigravitybatteries.com/pro...acker-lithium/ Lead/Acid Tracker https://antigravitybatteries.com/pro...ker-lead-acid/ You Tube

after some research on amazon, I decided to buy NOCO Genuis5 battery charger and maintainer. I was able to finally charge my battery (Napa charger/maintainer couldn't do it at all) within about 12 hours. The car started right away with no problem. The cigarette lighter plug cable for maintaining didn't work with this brand though, they have slightly different connector, ordered correct one.