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Old 08-02-2008, 12:44 PM   #1
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Question Is this a sign of a dying battery?

Guys, need your advise on that. This morning my car wont start. Battery was 10 vdc. I jump it with my other car, Boxster starts. Took reading on battery when running, I get 13.75 VDC steady with engine running idle. Stop car, reading goes down to 11.89 vdc and slowly going down by 0.1 volts every 5 minutes... Is this a sign of s dying battery?

Thanks for your help.

Thierry

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Old 08-02-2008, 01:01 PM   #2
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If it won't hold a charge, you should replace it.

Just don't waste your money on a Porsche battery.

Do a thread search and you'll discover that you can pick up a replacement one at Sam's or Costco for far less money.
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Old 08-02-2008, 01:32 PM   #3
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Quote:
Originally Posted by RandallNeighbour
If it won't hold a charge, you should replace it.

Just don't waste your money on a Porsche battery.

Do a thread search and you'll discover that you can pick up a replacement one at Sam's or Costco for far less money.
Or an optima that will last much much longer.
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Old 08-02-2008, 02:21 PM   #4
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It isn't necessarily the battery, though it most likely is as others have said.

The reason I say this is that the Bosch alternator should be putting out a charge of 13.5VDC-14.5VDC. But, it is usually more like 14+ VDC, so your reading is a little lower than expected, but still within range.

This could be caused by the battery, but for peace of mind, I'd first try to charge the battery on a proper charger and then see if it holds a charge. Also, if you later replace the battery, and the alternator reading is still under 14VDC, I'd keep an eye on it because this could indicate trouble with the alternator as well. Not white-hot critical, but it could keep you from becoming stranded in the future or messing up the new battery.
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Old 08-03-2008, 05:14 AM   #5
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Guys, since 12 cars, it's my first experience with battery problem, so I'm a little green with those problems.

Battery still in the car and plugged. Engine off
Took a reading direct on battery last night: 11.54 vdc.
This morning, still 11.54 VDC

Before I go and buy a battery charger, is this a sign of need to recharge the battery or need a new one?

The only thing I can tell you, that battery was in place when the alternator failed. Alternator is 3 week old now and seams to charge well (14 vdc). Do you think battery suffer due to the old intermitent running alternator and now need some help to reach and maintain 12 VDC?

Thierry
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Old 08-03-2008, 06:10 AM   #6
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Forget it, I'm on my way for a new OEM battery. I have an electronic volt meter & an amp reader that I normally use for AC. Is there any way I can use my amp reader on the main positive wire that is plug on the battery to look if there is current drawned out of the battery by something in the car? If not, is there another way to see it?

Tks!
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Old 08-03-2008, 06:30 AM   #7
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Any auto parts store should be able to run an electrical load test, free, to tell you if it's the battery or the alternator. It sure sounds like the battery to me.
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Old 08-03-2008, 11:09 AM   #8
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Thumbs up

Battery change...
Now get 12.25 VDC steady when engine stop.
14.35 VDC when engine idle

Thank you all for your comments and help. Team work is the way to go!

Thierry
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Old 08-03-2008, 11:36 AM   #9
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Tolum,

You did the right thing. You had a cell going out and even though, with a jump, the car will run-the battery was gone. There is a rule of thumb; 2% degradation (from 100%) per month from initiation (adding the acid). So anyone can figure out the % loss of their battery.

I had the same problem, my OEM battery was weak and was turning the starter over slow. After I replaced it the whole car seemed to wake-up and ran noticeable better.
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Old 08-03-2008, 06:06 PM   #10
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I just had this problem and a new battery will make a world of difference. The Porsche OEM batteries are too costly & not that great. Good luck in your choice!
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Old 08-04-2008, 11:52 AM   #11
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Almost the same topic,

The car has sat for 2 weeks, I know I know, it never sits but the MG needed to get driven.

Anyway, I drive the car Friday night after a few miles the battery and ABS lights comes on, after that the car drives fine. When the lights come on I notice the idle is going a little higher, after I give a little gas the lights go off.

It only happened a few times and all of them where at idle.

I assume a dying battery or alternator.

Hopefully a battery not a alternator.

What do you guys think?
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Old 08-04-2008, 11:59 AM   #12
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NEVER let a dying battery sit in your Boxster. My friend's S had a bad one and it caused all sorts of problems. If the ECU gets cleared due to a low battery, you will be up against a week and a half of trying to get the car running right again.
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Old 08-04-2008, 04:57 PM   #13
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Do you replace your battery at x age, say four years, just to not be annoyed? Or do you wait until it is going kaput?
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Old 08-04-2008, 06:20 PM   #14
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Well for me, anytime my battery is 3.5 yrs. old or older, at the 1st sign of trouble, I start looking for battery sales and replace it as soon as I can. A bad battery is just an annoyance for me, and one which is easy to avoid.
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Old 08-04-2008, 06:54 PM   #15
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Rock on LB, 3.5-4.0 years and I'm looking for a battery also.
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Old 08-05-2008, 08:12 AM   #16
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Quote:
Originally Posted by tolum
Forget it, I'm on my way for a new OEM battery. I have an electronic volt meter & an amp reader that I normally use for AC. Is there any way I can use my amp reader on the main positive wire that is plug on the battery to look if there is current drawned out of the battery by something in the car? If not, is there another way to see it?

Tks!
Ordinarily the way to check for a drain on the battery is to make sure everything in the car is turned off, disconnect the negative wire clamp from the battery, and put a tester between the clamp and the negative battery post. If there's no draw on the battery, no current will show up.

BUT... make sure you have your Radio Code (if your radio has one). Also, it takes awhile for the Boxster to turn everything off and I'm not as familiar as others in this forum with that element of this test.

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