altec914

How long should your battery in a 996 cab stay charged? I read somewhere around 5 days with doors locked and the alarm set. Is this true? Last owner had a battery tender but it did't come with the car but the manual was with the paper work.

Porschetech3

All batteries will "self discharge" with time. The general rule of thumb is 10% a month (in reality it is a lot less than this). Add @ 30ma battery drain for KAM memory of the DME, radio, clock ect. on a healthy car with no drain issues. This means a car battery should be fully recharged every 2 months or put on a maintainer if not used regularly, to keep the battery near full charge. Non-deep cycle batteries like to stay near full charge for the longest life.

Porsche 996 remote alarm system will go to "stand-by" after 5 days without being used, to conserve power. When in stand-by mode the alarm will not react to the remote signal until it has been "woke-up"..

griffo

If I know I'm not going to be using mine for over a week I disconnect the battery. If I don't it will be flat as a pancake.By disconnecting and connecting when I need it it stays charged for months.

Horsepwr

Parked mine in November, started it in April, no tender no issues fired right up.

AA717driver

I routinely leave mine for two weeks and no issues starting and no unusual indications on the battery meter (lengthy charging) upon starting.

TC

Porschetech3

A good/new battery can sit in a healthy car for as much as 6 months and still start the car, but will be damaged and not return to full capacity.

Griso8V

Mine will be dead after about 10 to 14 days. Not sure why but I need to have mine on a tender if I leave more than a week without starting, otherwise battery will be too weak to start the car. I have replaced the battery and it still needs to be on a tender.
Not sure why...

sparks259

Dead after only a week? Wow. My Interstate has never failed me after at least two weeks when I had my rotator cuff done. Gave a neighbor a thrill taking it out for a spin. Started right up.

Battery Guy

Battery manufacturer guidelines are six months before a boost charge is required with proper storage, based on 77 degrees F. Warmer temps will self discharge faster. If the battery is going dead in less than a couple of months there is some amp draw in the car.
This is for standard lead starting batteries - lithium batteries self discharge at a slower rate and should be good for over a year properly stored.
Daryll

Horsepwr

Dudes name is battery guy, he has to be correct!!! LOL

Battery Guy

Ha ha. Thanks! Been in some form of the battery business for close to 30 years now.
Daryll

mattsub

I can last about a week and then the battery is dead. I had the car checked and there’s no parasitic draw on the battery. I just spent the money on a battery tender and plug it in whenever parked at home.

fpb111

Porsche published draw =

Antigravity

Well... being blunt... you can try to ASSUME about how long a battery will last in a car, but its all relative and not very accurate by any means. It depends on the age of the battery, if there are after market accessories on the car. What year the car is.... because a 991 has a better on-board
"battery management system" than the previous models, and by that I mean it shuts down the systems on the Car more completely than the previous models, and will not discharge the battery nearly as fast. They went through a lot of effort ot improve this because the older models were drawing down the batteries fast. I know this because I have tested for this to the point of ridiculousness. Because we sell Lithium Batteries I had to know about how long the 30Ah model would hold a charge for in cars. What type of draws it was encountering and such. So this is actual testing. But as I found most all the cars are different and draw down alot depending on the accessories, year, brand and so forth.

On another thing, even if you have something as simple as a USB charger in your cig lighter that can create a significant parasitic drain. Or if you have a Camera, or radar detector connected it is a very large drain on the Car. Also Aftermarket Stereos. Its because on alot of Cars people or shop connect these devices without always considering if its a Keyed connection or not. We've seen some stereo work with out the key being turned on which can ad another level of parasitic draw on the battery.

So for your particular car, there is not saying.. but what I can say is if you have a 70Ah battery in good condition you should be getting absolutely more than a week... So something is going on there.

Now here my pitch....below is product we made called the Battery Tracker, this is the actual only way to know how longer your battery will stay charged and be able to know HOW FAST it is being discharged. WE made it because we are a Lithium Battery Manufacturer and saw how many people were needing this info.

It is a small Bluetooth device the connects to your Battery. Takes about 2 minutes to install the App and the Battery Tracker onto your battery. This device will give you a Read-Out of your real-time voltage, as well as your historical voltage over 31 days previous. So you might say "why do I need that?", but the fact is you don't have to open your hood to see the voltage of your car, no need for a Multimeter also... it sends the data to your phone automatically if you are within 30ft of the car. So you can easily see if your battery is running low. But additionally you have the History of 31 days in a Graph. So you can see every time the car was started, every time you drove it. How fast the voltage was going down during storage.... its all on the graphical interface. So say you drive your car, you going to see you voltage go up in the 14s or whereever it is charging at.... then when you stop you see your voltage sag back down to resting voltage.... then when you look at 2 weeks in storage you can see it drop from after driving and charging from 14.2v down to 12.8v and lower if it keeps going down, all in a easy to read graph in the App. Then you can also test your Starting Performance and if your Charging System is working.

So the Battery Tracker is actually the easiest way to REALLY see how your battery is actually draining , charging, and doing anything over the course of prior 31 days. You can see it here BATTERY TRACKER, we make them for Lead or Lithium Batteries, works on RV batteries or any 12v battery you need to monitor. Below is a video also