battery keeps dying

Hi, Im a new member and I need some help. I just purchased a 99C4 with 19K miles on it about 2 months ago. A few weeks ago the battery went dead. I jumped it and a couple days later it went dead again. After jumping it again for the second time, I made sure to start and drive it at least every other day. Then I had to go on a trip and whebn I got back it was dead. One of the other threads said that porsche batteries went bad without notice and were weak and recommended the opitma red top battery which I purchased and installed. I continued to start and drive it every couple days. Then I let it sit for about 5 days and it went dead with the doors locked. As many of you know, this is a total pain in the butt. The dealer sent two tow trucks and finally the service manager to get the car back to the dealer. The dealer is going through it, looking for what keeps draining the battery. So far they don't know what the problem is. Does anyone have any ideas as to what it may be? I though it may be a broken trunk or hood light that wouldn't shut off but that isn't it. they also ruled out the alternator. Thanks

I have no idea what the cause might be, but it might be wise to have a "trickle charger" handy. I use one now if I know I'm not going to drive for a few days.

A five year old battery is a five year old battery -- regardless of miles. My MY99 has 14k miles and I expect the battery to go any day

well, i replaced the battery with an optima red top just a week ago and it went dead also, so it isn't a problem with the battery. THe althernator looks okay too because if i started adn drove it every few days the battery looked good. Thanks Bobby

My OEM battery had to be replaced after only 2 years. The service guy told me that Porsche OEM batteries are not designed to last very long and that they have much lower CCAs than many other batteries. If you have an older battery and don't drive the car but every 5-7 days the battery will discharge. I have since bought the Porsche Battery Maintainer and I've had no problems. BTW, the dealer replaced my battery under warranty (100% free of charge). I always thought that battery warranties were pro-rated.

You have a power drain then. Best start looking for the obvious -- like the front trunk light no shutting off (broken switch), rear light, etc.

I, too, bought a 1999 C4 a couple of months ago, and I'm having problems with my battery dying frequently. It seems that if I don't drive my car at least every couple of days, the battery will die. I have 20K miles on the car, and it's on its second battery. I'm bringing it to the dealer to have it checked out on Monday. So if I find out anything useful, I'll let you know.

what are some common battery drains that I should be looking for?

A coomon drain is leaving the key in the ignition after you turn the car off. But since you said the car was locked.....

Dealer says that there are so many computers onboard that there is a natural power drain even with all lights & ignition off. They recommended starting the car and letting it idle for 5-10 minutes at least every 5 days if I'm not going to drive it. Either that or use the trickle charger.

That's crazy. I have a LS400 with 175000 miles on it and if I leave it in the garage for 2 weeks it starts right up. Your telling me that if I leave my 911 for 3-5 days that it won't start at all. Not only is that terribly inconvenient, but it is also dangerous. My battery went so dead after sitting for only 5 days that it had to be towed to the dealership because the hood would not unlatch. Sorry to b*tch but although the car has awesome performance, I might need to get something else if the car dies like this. The trickle charger is for long term storage so that the battery will not go bad, and is not for daily use. It is a temporary solution to the problem. My SC430 sits for weeks in the garage in cold Chicago winters, starts right up and I know that thing is one big computer that drains the battery. The dealer is looking for the prob as we speak but has come up with nothing. Thanks for your suggestions as of thus far though.

Chit, your experience is atypical. I own an 02ttX50 that will go flat in 2-3 weeks, but not in the few days you describe. You clearly have a drain. I'd go over the really simple things first (speaking from experience-having left an under dash interior light on in my son's Alfa and going thru your process) Like- no cell phone charger on, headlights and turn signals definitely off. I'd look at the car in a darkened garage after turning it off to see if there are any hints. After that it will be up to the dealer. By the way, I have a BMW 850 that will go a little longer before going flat...but it has 2 batteries in the trunk. AS

you guys think that a battery cutoff switch would help if you don't drive the car for periods of time. I dont' care for radio settings much. Here is a link to what i am talking about http://www.performanceproducts.com/P...producttype=10

I have a 99 C2. I have left it sit for up to a month at a time, the keyless entry stops working and the blinking light on the dash goes out automatically. That said, it always had started on the first try, original battery. Maybe I'm lucky, but the dealer bit about constant computer drain sounds like bs to me. Happy hunting...

If everything is right it should start after sitting a month or so. The computer shuts down most of the current drains after it sits 5(?) days. Are you leaving anything pluged into the lighter?

Nope, nothing. I called the guy on Friday. He let it sit for 2 days and the battery was dead so he said there is a definite battery drain. He is gonna go through it next week. I'll tell you what he says but please let me know of any ideas you guys can think of.

car has been at the dealer for almost a week now. The manager let it sit for 2 days adn it went dead so he confirmed the drain but has yet to find it. Has anyone had this problem before?

just a thought.... maybe you have a bad alternator (not charging up the battery during driving) which would eventually run down any battery. experience: old VW GTI bad ignition switch which messed up the electronics which messed up the alternator which messed up the battery..... can't say a Porsche is the same as a VW but those Germany guys get around. otherwise try the trickle charger (works well for me).....too many weeks of sitting idle and frequent run-downs will kill most batteries.

I had my 996 C4 in the shop yesterday for them to check why my battery keeps dying, even after just two days w/o driving my car. They said that my electrical system was just fine, and ultimately I need a new battery (even though my battery is <2 years old). They said that Porsches are notorious for drawing a significant current even when the car is off due to the computer, radio, and a few other items. Still, it seems that a battery should last for more than 2 years without dying every couple of days. Anyway, the bottom line for me is that I need to either drive my C4 every day to keep recharging the battery or get myself a trickle charger that I use regularly. In the meantime, I need to buy a replacement battery.

If it's gone flat a number of times, you could need a new battery that often. The unanswered question is why is it going flat so rapidly? Eagerly await the dealer's solution. AS

bpr, that doesnt' sound right though. Several others have said that they leave their cars sitting for several weeks without a problem. Although there is a battery drain it shouldn't drain it so rapidly in 2 days that you can't start the car. I replaced my battery with a new optima battery a week before sending it to the dealer and it went dead within a couple days again. Thats why I don't believe the battery drain explanation. I don't think my alternator is bad either because if I start it every day there are no battery issues. I'm gonna call him later today to see if they found anything. If I were you I'd change the battery out immediately and see if your problem is solved.

Chitownbob, I was under the impression that Optima didn't make a battery to fit Porsche's. I'd be very happy if you tell me I'm wrong. By the way, congrats on your Cubs win. Pat

Thanks, Im a White Sox fan but am cheering for the Cubs. Optima doesn't make a battery that fits the 996 exactly but there are instructions somewhere on this site that shows you how to do it. Underneath the battery is a removable battery tray. I removed it, drilled a hole into it and then secured the battery to the tray directly with a screw. The optima battery came with holes on the bottom. THen i just reattached the tray. The instructions called for replacing the positive cable becasue it was short but I was able to use the owm cable. Its not a perfect fit but works well. I chose the optima becasue it was more powerful than the OEM battery. Also it was sealed so I didn't need to worry about battery fumes getting into the cabin. You have to be careful of that because if you notice, the air filter for the HVAC is located directly next to the battery. Bob

chitownbob -- I agree that it doesn't sound right that my battery is draining so quickly. I'm getting a new battery tomorrow and will see if that solves the problem. If not, the car will go back in the shop for them to diagnose what's at the root of the problem.

chitown It sounds like you have a drain problem. Often the light in the luggage or engine compartment. Once a battery goes dead, there are good odds that you damage the cells and it will not take a charge ever. My 993 could go about a month without being started. My GT2 about three weeks but I have a (mandatory) tracking device which always drains some current.

Its been two weeks with no drain found. What is the procedure porsche uses to find such problems? Is there some diagnosic's program that can be used? Thanks Bob

First you disconnect a battery terminal and connect an ampmeter to measure the drain in milliamps. Then, watching the meter you pull fuses until you locate the circuit causing the drain. Be sure you have the radio code.

Hey ebaker Which battery terminal do you disconect. I am not an engineer so I don't understand how the ampmeter would locate drain when the battery is disconnected? THanks Bob

Didn't see this mentioned previously but it happened to me so I 'd thought I'd jump in. My battery was going dead after 2-5 days when I first got my car. It turned out to be my V1 that I always left on! I was able to leave previous radar detectors on all the time without a problem but I was told the V1 drains more power. Maybe you removed the detector before bringing it to the dealer and therefore the service department ruled out that possibility?

I thought it was the radar also but the drain has been happening for the last month or so. I had a k-40 installed which shuts down with the ignition within the last month so it has nothing to do with the radar since the problem started before the k40 was installed. thanks for the input though. bob

The amp meter must be put into the circuit in series so the current that is being measured goes through the meter. I'd disconnect the negative terminal and connect one meter wire to the bare battery terminal and the other to the battery ground cable. Most amp meters have a maximum current that if exceeded it will blow a fuse in the meter. Don't turn on any high current devices with the meter connected or you will blow the meter's fuse. After you figure out which circuit is causing the drain you'll have to study that circuit on a wiring diagram to try to figure out which item is using the current. You can spend hours trying to track it down.

Same problem here, couple of days sitting in the garage, flat battery, I suspect the alarm system. Even when not activated it still drains. Understand that older alarms are even worse. 911SC, 78

Just got the car back. The dealer said that it was the installed cell phone in the car. He removed it and let it sit for several days and said it started right up. It been at the shop for 3 weeks so Im gonna drive it but next week I'll let it sit for 7 days to make sure the problem is gone. Bob

Your post remined me of an STS which used to die after several days sitting and also turned out to be the built in 3 watt cellular amplifier which the handset plugged into. I used to detach the booster power lead when I was leaving the car for travel etc.

Do I get brownie points for my call on "no cell phone charger on"? Had that problem on a Suburban. Thanks for the update. AS