Dennis C

I find my 996 C4S to be a reliable vehicle most of the time. That being said, it seems to be really hard on batteries. It's not a garage queen that is rarely started - this car is my daily driver.

This morning, I went out to the garage to start up the car to go to work and the battery didn't have enough juice to crank the engine. It was just driven on Saturday and it didn't have an issue.

My batteries seem to last for roughly 18 - 24 months. Is this normal? Perhaps I have a failing alternator or a slow power drain somewhere...

My Cayenne is also hard on batteries, but it's not as bad as the C4S.

fpena944

Dammit Dennis you jinxed me!

I was thinking to myself how I've had good luck with mine. But of course mine died in my parking garage at work.

On my way to buy a new battery now. Anyone know the sizes of the nuts on the terminals and the one in front of the battery? I want to make sure I have the right tool sizes.

hollmatt

I had my original 2003 996 battery go after 9 years...was hoping for 10.... It's plugged into a battery tender when not in use.

heligear

The posts are 10mm, sorry can't remember the size for the bttery clamp

G Demler

What brand of battery? I use the porsche battery and get 3 - 4 years out of them in the hot Florida weather and drive it somewhat seldom. My garage swears by interstate batteries

Dennis C

I've always used the Porsche branded batteries from my Porsche dealer. I think it might be time for me to consider another brand.

Mine's connected to the smart charger now. It only registered 10.6 volts when I connected the charger. It's up to 14.7 volts now. Hopefully it just needs a charge and then it will be good for a little while. I last replaced it on February 6, 2013. I'm not sure how long the warranty lasts on a Porsche battery, but I think it may only be one year.

Ahsai

Dennis, a few things to check. What does the voltmeter or the one in the cluster read when the car just started, at idle and at speed? Say with low beam and a/c ON? If it's 13.5v to 14.5v, then it's likely your charging circuit is fine. Typically they last at least 3-4yrs. If driven daily, they could last 5 to 6yrs. If the charging is fine, most likely you have a parasitic draw.

Any aftermarket electronics on the car such as amp, radar detector, lojack, etc?

Ahsai

Sorry but that doesn't count A lead acid battery doesn't deteriorate much if it's fully charged all the time.

Dennis C

The volt meter in my cluster typically reads right around 14 volts when the car is running. I have noticed that right when the car starts, it tends to drop down into the low 12 volt range, but it quickly goes up to the 14 range after that.

Ahsai

Do you have any problem starting the car if you leave it parked for say 10 days or longer?

Dennis C

I don't think it has gone for 10 days without being started since I've owned it.

The longest that I recently let the car sit without starting was 7 days, and it started up without any issues.

Capt. Obvious

The longest I've let either of my 996s sit without being driven is about two weeks (on a couple occasions). Both fired right up after sitting that long.

My car regularly sits for at least 5 days, with doors locked and alarm on and I've never had a dead battery.

silotwo

I hope this isn't a jinx topic. I am at 7 years on an O.E.M. battery in the C2 and never had a problem as a daily driver for 5 years and it still seems strong although it is driven only a few times a week. I have never used a battery tender and we do see extreme temps here in both winter and summer. Oddly I was just thinking about replacing it as I really didn't expect much more than 5 years out of it.

The battery in the C4S is also O.E.M. and about 3 to 4 years old with no issues.

Both of my cars do show a voltage drop immediately after starting but quickly rises to 14v plus then settles in at what looks like about 13.5v.

Ahsai

If you have a low current DC amp clamp, it's super easy to check parasitic draw. If not, I would consider non OE batteries such as costco, interstate, duralast, etc.

MiamiC70

I had to change my bought new Diehard Platinum out at 3 years +/-.