isseps

I bought my 04 996TT cab last year with 25K miles. It's a CPO. Yesterday I took it to the office and had no problems. This morning it would not start. The battery seems dead. I poped the hood and the battery is an Interstate with 85 months of warranty. Obviously not the original battery. Even if the original lasted for only 4 years, this battery can't be more than 3 years old and I have a Porsche maintainer on it too. I had the auto club tow it to the dealer. Do you think I may have a short in the car? Anyone with a similar issues? Thanks.

Macster

Well, I might be more pessimistic than most but imho the battery did its job. Its 85 month warranty sucked you in and when you take the battery back and get some credit you walk out with a new Interstate battery.

The idea is not to sell you a battery that lasts but a battery that doesn't and brings you back to get credit and another battery, over and over and over again.

Sure there might be an electrical problem. You'll have to check for excessive parasitic electrical loads with everything off and check the alternator delivers suitable power to charge the battery and supply the car's electrical needs while running.

I have an Interstate battery in my 03 Turbo. Car (used) came with it. Not my choice. As soon as the Interstate battery requires replacement I'm going to yank it out pronto. Not sure what I'll replace it with. I've had good luck with the OEM battery in my 02 Boxster. The battery lasted around 7 years. I might just drop in an OEM battery onto the Turbo and see if the good battery life repeats.

Sincerely,

Macster.

ltc

Batteries are usually good for about 5 years, give or take.
Failure modes are due to mechanical/vibration (cracked/shorted plates) and electrochemical (improper type of electrolyte, improper charging, etc).

On a more recent note, most batteries are no longer using virgin lead; rather reclaimed/recycled lead...which is not as good as virgin lead from a plate perspective, so again, problems will occur.

If you want something a bit more 'reliable' and have about $2400 available, Porsche will sell you their Lithium based lightweight battery, which should be a bit more reliable.....
http://www.suncoastparts.com/product..._Code=997TURBO

okbarnett

they go fast if you dont drive the car a lot. it could have a shorted cell in a day

MitchW

I have an 04 as well, and it is on its 3rd battery. I've put a trickle charger on it, but hard to tell if it is working as the new battery is only a few months old. Be sure to keep the car locked when you are not using it as it will use a fair amount of juice when not locked with the alarm armed.

brooklynkid

same problem. i bought a 04 TT cab last august and its interstate battery lasted until march. I agree if car sits long the battery just dies

BostonDuce

FWIW, I was able to use a CTEK 7002 changer set on "recondition" to bring a battery back to life that refused to take any other charging method.

That Porsche lithium battery was interesting until I found out that it doesn't work below 32 degrees. Porsche says you have to change it out during cool months.

BD

theporscheguy

My battery has been showing signs of weakness although I only take the car out on weekends. I figure with my use any battery I put in it will need a maintainer to make it last more than a year.

Michael-Dallas

Everything you wanted to know, and then some: http://jgdarden.com/batteryfaq/carfaq2.htm#die

That entire site is a wealth of good info on automotive batteries.

/m

isseps

So they replaced the battery with a new one about 45 days ago. Last week I was out of town and the car sat in the garage unlocked with key in the ignition. When I got into the car, the battery was totally dead. Normal?

Macster

Can't say. I've never left the key in the ignition for more than a few moments if I'm not going to start the engine and drive the car.

The key's presence might keep more of the car's electrical systems "alive" (powered up) and the parasitic load that is normally present can be increased substantially.

For instance, if the Ecu is alive it can draw considerable power that can have even a top tier/top notch battery dead in just a few days. (Since I write firmware for vehicle test equipment I have to be very careful I avoid 'talking" to the car's various controllers due to spurious signals lest I wake up the engine/drivetrain controllers and run down the battery.)

Unless someone chips in that he's left his car parked with the key in the ignition and has had no battery problem I'm going to suspect the key in the ignition caused the battery's premature demise.

Sincerely,

Macster.

Mikelly

What I was told, by both Porsche technicians and two indies, was that you're best bet for a healthy battery were to LOCK THE CAR with the keyfob even when the car is sitting locked away in the garage. I was told that when the car is unlocked, the locking interface allowed the multiple computers to "chatter" back and forth to confirm that they're still all active and ready to perform. A strong battery sill drain slightly. A weak battery will die a quick death within 12-18 hours.

I don't know this is the case, but my current battery was recommended to be replaced two years ago, and I've kept the car locked when I'm not near it (much of that time sitting without running) and the battery still registers the required voltage.

Mike

wross996tt

If you leave the key in the ignition the battery will be dead in less than a day...normal. I leave mine unlocked with an interstate maintainer and it works like a charm.

911SLOW

Very normal. When you forget the key in the on position the power consumption rises and can kill a 60Amp /70 Amp battery in a matter hours to few days depending on the car.

John

dantzig

Slight modification of the above... If you just turn off the key and leave it in the ignition, it will indeed drain the battery quickly as the folks above have said. However, if you turn off the ignition, remove the key, and then reinsert it without turning it, then it will not drain the battery any more than if it were removed.

If you lock the car with the key fob, as Mike said, then after a couple of days the car will go into a deeper sleep mode and consume less power.

Jon