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Typical Battery Life?

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Hi there,

I have a 2003 Boxster S (986) and it's coming up to the 5 year mark. It's a daily driver for me so it has about 50,000 miles on it (80,000 km). In the recent months, I have been driving the car significanlty less and sometimes about once a week, and only for short distances (maybe 10 miles each trip).

It's been dealer serviced since day one until the warranty expired about a year ago. Anyway, this morning, when I tried to start the car, I hear a solenoid click when I turned the ignition key but the starter did not crank. After a few more tries, I hear the starter slow-crank a couple of times but still no luck (so starter motor should be OK).

I consulted my Bentley's Boxster manual and did an open-circuit voltage check to find the voltage to be about 9.5 volts, which suggested a drained battery, which led me to come up with 3 possible scenarios: drained battery, faulty battery, or bad alternator. I bought a battery charger and it is charging the battery as I type. Hopefully, this can get my car started.

However, I wonder if there is any easy way to test for a bad alternator without any sophisticated tools? My worst fear is that I drive my car out and it gets stranded outside. Is 5 years a pretty normal time to replace the battery? Does the make of the battery matter that much qas long as the specs are matched?

I recently did some minor servicing on the car myself: oil & filter change, pollen filter replacement and air filter replacement (disengaged the soft top and opened the top engine compartment). Would this have anything to do with this problem by any chance?

Any help and pointers will be greatly appreciated!

Edited by primate
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Batteries for year-round daily drivers typically lasts longer than 5 years. I just replaced the original battery on my 1999 Boxster after 9 years (105k miles) and this battery life has been approximately the same for my last 5 cars.

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I'm with Loren on this one

I've owned probably 25 vehicles over my life and 5 years is a long time for a battery to last. My 2002 Acura has had its battery replaced. My 2001 Boxster likewise.

I'll grant daily use is better for the battery, but a prophylactic replacement at about 4 years just before the next winter is not an unwise thing IMHO.

I wouldn't even bother further testing, I'd just replace the battery based on the voltage reading.

You can do it yourself and don't have to use the dealer's overpriced replacement batteries.

A list of batteries known to fit is at the beginning of this link.

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Thanks Loren and everyone's replies. I appreciate it!

Well, the good part of the story is that I managed to get the car cranking and running after an hour's worth of trickle charging. That one hour charge brought the battery up to about 12.4V open circuit and about 14.0V with the engine running, which is within the general range of 13.5-14.5V for a working alternator. So the good news is that the alternator need not be replaced ... yet.

As for the battery, I think I will heed everyone's advice and pick up a new one. The one I have now is the original Porsche-branded Moll battery. Is there any specific brand recommendation for a replacement?

Thanks again!

The following is Porsche's test spec for the vehicle battery (from TSB 4/02 2706 Battery - Maintenance Checklist -- dated 3-7-03)


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  • Moderators

Look here first. http://www.renntech.org/forums/index.php?showtopic=2950

Your S probably has the 80 amp hour Moll, so then look here. http://www.renntech.org/forums/index.php?s...amp;#entry88098

If you want to test your 5 year old Moll then put it on a real charger, like a 10 amp charger, not a trickle charger. Then bring it down to a parts place for a load test after it is fully charged.

But a 5 year old Moll is living on borrowed time. And sometimes the Moll goes boom....


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Mike's guide is excellent. One thing that I would add is that if you're in the store and you see a battery that has the exact right model number but it has an "R" on it, don't get it. "R" means that the battery terminals are reversed. That means the battery cables won't reach the proper sides.

(Note that with the Optima battery, unlike with the other brands, you are supposed to get the "R" model, not the non-"R" model)

Edited by Stefan
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