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Old 09-01-2010, 02:27 PM   #1
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Another Dead Battery Thread

I realize that there are numerous dead battery threads here, but my situation is slightly different.

I only drive my 07 Boxster S on the weekends, and sometimes not for 2-3 weeks at a time. I know that is hard on the battery. So when I couldn't get it to turn over a week or so ago (I did get a solenoid clicking and the instrument lights worked), I figured that the OEM battery was shot. Got the correct Interstate replacement battery, installed it and everything worked great, or so I thought. The car started right up, and I drove it about 60 miles that day without a hitch. The following weekend, I went to start the car and it was dead as a hammer. No solenoid click, no radio, no instrument lights, nothing. I couldn't even extract the key from the ignition.

I got jumper cables to open the hood, and a battery charger to recharge the battery. The battery took about 12 hours to charge on the 6 amp setting, which seems about right. When I connect the battery the alarm goes off and everything seems to work, but I still am concerned.

What could have made the replacement battery go COMPLETELY dead so quickly? I am afraid something is putting a big drain on the battery while it is parked, even though I lock it to shut everything down. Could the battery be defective? If it was the alternator, wouldn't I get an indication on the dash? Any thoughts or previous experiences would be appreciated.
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Old 09-01-2010, 10:47 PM   #2
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Bad batteries will cause the alternator to fail. Using the car as you describe can kill a battery and the alternator.

There are so many ways a battery can go bad, any battery 3-5 yrs. old is suspect, regardless how little you may have used it. Even the shock and vibration a battery experiences is detrimental and can kill it.

Plus, a battery has only about 5 - 7 discharges in it before it's done for. Each time a battery discharges, it loses it's ability to hold a charge, according to the SAE, by 15%, and the effect is cumulative.

I'm guessing you need an alternator and a starter (ignition) switch from what you describe. The new battery was not being replenished by the alternator. Chalk up 1 discharge.

These cars do have a constant energy drain from the alarm, radio, DME, etc., and this drain is significant, 2-3 weeks can drain the battery. Best thing to do is have a maintainer (not a charger) which you can plug into the lighter socket to maintain the battery health between use.

Cheers!
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Old 09-02-2010, 04:58 AM   #3
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What could have happened

You don't use the car much and there is a constant drain even while parked and everything off (you don't have any aftermarket additions, chargers, etc that could be drawing extra power do you?). The draw shouldn't be enough to prevent starting based on my experience but then I have a good fresh battery, a tested charging circuit and I always drive 12+ miles when I take mine out for a run...usually 50 miles one way. Mine has been sitting for 2-3 weeks and starts immediately. It was not on a battery maintainer.

Check the fluid level in the battery. Most sealed batteries evaporate over time.

So the next thing to do is get the battery charged and check the voltage. Bad, go get a new battery. Then, if fully charged and right voltage, get it load tested and the output voltage of the alternator checked. If those all check out, then you go chasing what is causing the current draw by testing all the circuits by pulling a fuse at a time and noting the change with an amp-meter in the circuit between the battery and the car. A table of expected circuit draw is located here .
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Old 09-02-2010, 07:18 AM   #4
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Quote:
Originally Posted by mikefocke
You don't use the car much and there is a constant drain even while parked and everything off (you don't have any aftermarket additions, chargers, etc that could be drawing extra power do you?). The draw shouldn't be enough to prevent starting based on my experience but then I have a good fresh battery, a tested charging circuit and I always drive 12+ miles when I take mine out for a run...usually 50 miles one way. Mine has been sitting for 2-3 weeks and starts immediately. It was not on a battery maintainer.

Check the fluid level in the battery. Most sealed batteries evaporate over time.

So the next thing to do is get the battery charged and check the voltage. Bad, go get a new battery. Then, if fully charged and right voltage, get it load tested and the output voltage of the alternator checked. If those all check out, then you go chasing what is causing the current draw by testing all the circuits by pulling a fuse at a time and noting the change with an amp-meter in the circuit between the battery and the car. A table of expected circuit draw is located here .
Mike--Thanks for the response and the great link. However, I didn't see any table with expected current draws there. Is there another link?

Last night I reconnected the battery after charging it and letting it sit for 24 hours. I measured the voltage across the terminals at about 13V after I connected it. After starting the car, the voltage jumped up to slightly over 14V, so it appears as if the alternator is working. My next step is a load test? Do I have to go to the dealership to get that done, or should any battery shop be able to do that?
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Old 09-02-2010, 07:20 AM   #5
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Originally Posted by Lil bastard
Bad batteries will cause the alternator to fail. Using the car as you describe can kill a battery and the alternator.
Can you be more specific? What did I do that could kill the battery and the alternator? I realize that complete discharges are hard on the battery, but what should I have done differently?

Last edited by socalsharky; 09-02-2010 at 10:17 AM.
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Old 09-02-2010, 10:42 AM   #6
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Quote:
Originally Posted by socalsharky
Can you be more specific? What did I do that could kill the battery and the alternator? I realize that complete discharges are hard on the battery, but what should I have done differently?
Yes I can. The alternator is designed to come on and off. In the off mode, it essentially freewheels and stays nice and cool because it's not generating any heat to produce electric current. If you look carefully at the alternator, you'll see it has it's own fan built-in to provide cooling, keeping the bearings and the circuitry (diode pac) nice and cool. Believe it or not, these things can produce a lot of heat. So much so, that there are currently several cars on the market which use water-cooled alternators.

If the battery is significantly drained, even though it's not discharged, it makes the alternator work longer just to replace the current in the battery. Add to this that even a partially drained battery can upset it's internal chemistry so much that sulphate crystals (from the electrolyte) can form on the lead plates. This lessens the amount of surface area for the necessary reaction to take place. So, in addition to being low on current, it now has a lessened ability to 'make' that current, meaning the alternator has to work even longer. Then, with a weakened battery, it's ability to absorb electrical fluctuations (or act as a buffer) is also reduced, placing the diode pac in the alternator under greater stress, making them die prematurely.

One problem many people have is that they view the battery and alternator as separate components instead of equal and mutually dependent partners in the charging system. Most people believe that a bad alternator killed their battery, when more often, it's the exact opposite - a bad (or less than optimal) battery is what killed the alternator.

I know it will seem like overkill to many people, but if leaving the car for more than even 48 Hrs., the battery should be either disconnected (which people are reticent to do for fear of losing the radio pre-sets and DME adaptive memory) or plugged into a maintainer, which many feel is cumbersome. This is why the type which plugs into the lighter socket is a good idea, it's convenient.

After 48hrs. the battery is still usually capable of starting the car and this is most people's gauge of their battery's health. But they are ignorant of what it may be doing to the alternator over time by making it work 'longer'. And even their car's range (MPG) can suffer, because an alternator when 'energized' (working) has a parasitic draw of between 3 and 8 HP crank HP which could have been used to drive the rear wheels. So, the shorter the alternator's operating time, the more fuel can be used to actually propel the car. This may only result in 5-10 more miles/ tankful, but it is measurable.

Cheers!
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Old 09-02-2010, 11:11 AM   #7
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Originally Posted by Lil bastard
Using the car as you describe can kill a battery and the alternator.
Thanks for the detailed reply. I just take small issue with your statement about "using the car as you describe...."

I am an engineer (though not an EE) so I totally understand the electrical circuitry of the car. My point was that I operated the car for the first three years of its life exactly as was intended by the manufacturer (other than not driving it everyday, which I'll grant you could be significant). When I realized that the battery was dead, I did not attempt to jump it, but rather bought a new battery. When that battery discharged, again I did not jump it, but hooked it up to a charger, in order to save the wear and tear on the alternator. So other than using a battery tender since the car was new, or driving it a lot more frequently, there was really nothing better that I could have done, right?

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Old 09-02-2010, 12:05 PM   #8
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Quote:
Originally Posted by socalsharky
Thanks for the detailed reply. I just take small issue with your statement about "using the car as you describe...."

I am an engineer (though not an EE) so I totally understand the electrical circuitry of the car. My point was that I operated the car for the first three years of its life exactly as was intended by the manufacturer (other than not driving it everyday, which I'll grant you could be significant). When I realized that the battery was dead, I did not attempt to jump it, but rather bought a new battery. When that battery discharged, again I did not jump it, but hooked it up to a charger, in order to save the wear and tear on the alternator. So other than using a battery tender since the car was new, or driving it a lot more frequently, there was really nothing better that I could have done, right?
You are doing all the right things... especially avoiding a jump start.

I learned the hard way with my 2000 S that I can't leave the key in the ignition. Doing so - even in the off position- apparently keeps a bunch of electronics active and fully drains the battery in a matter of days. Now, after putting in an Optima battery, I always take the key out and have not had another drained battery issue. Even if the car wasn't run for 3 or 4 weeks. Your year may be different, but are you taking the key out of the ignition when you finish driving?
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Old 09-02-2010, 01:41 PM   #9
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Quote:
Originally Posted by socalsharky
Thanks for the detailed reply. I just take small issue with your statement about "using the car as you describe...."

I am an engineer (though not an EE) so I totally understand the electrical circuitry of the car. My point was that I operated the car for the first three years of its life exactly as was intended by the manufacturer (other than not driving it everyday, which I'll grant you could be significant). When I realized that the battery was dead, I did not attempt to jump it, but rather bought a new battery. When that battery discharged, again I did not jump it, but hooked it up to a charger, in order to save the wear and tear on the alternator. So other than using a battery tender since the car was new, or driving it a lot more frequently, there was really nothing better that I could have done, right?
Well, that's right. I'm not slamming you at all, but have to say that these habits (infrequent driving, no maintainer) are less than ideal. Just explaining how your habits could contribute to the issue.

Again though, you are describing a battery which is drained because it would not start the car and discounting the cumulative effect (3+ yrs. in your case) of operating a battery which was at arbitrarily say, 60-70% (or whatever) a good portion of the time.

Both the battery and the alternator, each separately and together, suffer from this for the reasons I described. Realize that batteries are fairly precise - a healthy cell in a 6 cell automotive wet cell battery will produce between 2.1 and 2.2 VDC. This means a healthy battery will output between 12.6-13.2 VDC on a DMM (ign. off, key out) - this battery is 100% charged. If you measure only 12.45 VDC, the battery is only 75% charged. At 12.06 VDC, the battery is only 25% charged, yet most people think that this battery is OK because it's putting out 12 volts.

To measure the alternator, use a DMM set to VDC and read across the battery terminals engine running. The Bosch alternator spec is: 13.5-14.5 VDC.

3 Yrs. is the short side of a battery's life, though just beginning to enter the 'normal' reliable life expectancy zone. But, if it turns out your alternator is also kaput, 3 yrs. is definitely a premature death.

Something caused this. It could all be that the alternator was faulty to begin with and the battery too. Or that a sudden shock to the battery (pothole, speedbump, extreme environment, etc.) degraded it contributing to alt. failure. But, these are unusual. If the car were driven 3 times a week, 15+ miles/trip, these things would outweigh the possibility that a less than optimal battery was the culprit.

As an engineer, you are fully aware that machines in general tend to predominately fail at one of two points - their infancy or old age. The former because of a fault in material, design or manufacture, installation or application the latter because they simply wore out. If the failure occurs in-between, there is usually an external cause.

IIRC, the ign. off current drain is 60 mA after 10 min. (when the lights and such turn off). This is easily measured at the battery terminals w/ a DMM - disconnect one terminal and connect the DMM to the cable and the battery terminal. If the draw is higher than 60mA, suspect relays which are stuck on, other components like the radio (1 guy reported a 700mA current draw and it turned out to be his radio), even a bad diode in the alternator can cause ign. off current draw. To isolate the cause, start pulling fuses and relays one by one and notice any effect on the DMM value.

Again, using a DMM w/ AC capability, switch to AC and check voltage across the battery terminals with the car running. If you get any value other than zero, one or more of the diodes is bad and allowing current to reverse flow, even with the car off. Another check if you don't have an AC capable DMM is simply to measure the battery and then disconnect the negative terminal and leave it a day, then come back and take the measurement again. If it is the same, there is an issue with the car, if lower, the issue is with the battery.

Cheers!
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Last edited by Lil bastard; 09-02-2010 at 06:54 PM.
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Old 09-02-2010, 01:56 PM   #10
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battery tender

you may want to consider buying and hooking up a battery tender during the periods when you are not driving it.

secondly as previously indicated, there are a number of systems that remain active if you leave the key in the ignition. IIRC there was some info suggesting that its best to remove the key and lock the doors, thus allowing the systems to sleep, and reducing the battery drain.
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Old 09-03-2010, 09:43 AM   #11
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Definately put it on a battery tender if it won't be driven for more than a week.

Lil', your facts make sense, but if driving off on a flat battery kills the alternator, Boxsters have another fatal flaw! I've done just that on my '94 Integra ( and various other cars ) more times than I can count, with never a problem, and it has 200k miles on it, and the original Alternator. I do agree it's a bad thing to do on a regular basis. ( What can I say, it's a beater, and doesn't get the love it deserves! )
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Old 09-13-2010, 08:13 AM   #12
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I just wanted to update this thread with what I hope is the final solution:

After the battery continued to discharge itself at an abnormally high rate while sitting, I took the Box into Hergesheimer in Lake Forest, CA. I had not dealt with them before, but they really seemed to know what they were doing and treated me very well. They hooked up the car to the computer and got 3 or 4 pages of diagnostic errors! Later it turned out that most were due to the fact that I had disconnected the front trunk light when I was going through my diagnostic process. The fact that the light was disconnected completely confused the car's computer, which kept it using far more power than it should have been. Hergesheimer load tested the battery (the new Interstate) and tested the alternator, and both are fine. Nothing definitive could be found to be wrong with the car. They cleared all of the error codes. In the end it appears that when the first battery died, it created an error code in the computer that never cleared. The disconnected front light bulb created more computer confusion that increased the idle current draw. Additionally , the replacement battery may not have been fully charged when I got it.

I now have the car on a battery tender. It showed that it was charging the battery for about 24 hours and now it is in maintenance mode, so that looks good. Hopefully that is the end of the story.
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Old 04-17-2012, 05:52 AM   #13
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This is an old post, but i like to ask question from the experts.

First time i have a dead battery. Of course i freaked out. After figuring out how to open the trunk, then I charged the battery.

Got the car to start, now these are the issues i have now:

1- PSM failure - when away after driving around the block.
2- Heat seats are not working.
3- headlights washers are not working.

Anything I can do to avoid to go to the Porsche dealer?

thanks,
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Old 04-17-2012, 06:20 AM   #14
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Did you check the fuses? Maybe one blew and those items share the circuit.
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Old 04-17-2012, 06:50 AM   #15
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Possible causes:

*Blown fuses- replace

*Scrambled DME memory due to low voltage- Check and write down any OBDII Error codes. Disconnect battery for 5 minutes and reconnect

*Rodent damage to wiring harness causing short to ground.

Add in... Also possible failed ign switch.
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Old 04-17-2012, 11:27 AM   #16
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many with dead battery have hard time opening the front trunk. This has happen to me once. as a result of this experience, I made (I believe you can purchase fully built up unit) a connection into the cigarette lighter socket. Most cars have this socket active with or without the ignition switch.

Most likely, there's plenty of thread here and in other forums. This is what I did.
I have many useless cell phone car chargers. I took one apart, and removed the guts and soldered wires to the two contacts.
went to Radio shack and purchased male/female connector pair and soldered the battery tender wires to a connector.
On the cigarette lighter adapter side, soldered the mating connector to the wires.

This allowed me to "charge" overnight the battery without the need to open the trunk. My car is 01 so the trunk opens with a switch. I would had to dig behind the front wheel well for the emergency cable. but with the cigarette adapter, no need.

if the battery is dead to below some voltage, the battery tender would think that the battery is shorted and will not energize the wires.
in this case, I had an AC to DC adapter 2A at 12VDC and connected it to the lighter adapter for few hours and then switch to battery tender.

Since my car is my daily drive, the battery tender is connected to my other car sleeping in the garage for months at a time. That car starts up strong every time.

Tad.
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Old 04-26-2012, 12:09 PM   #17
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My Porsche mechanic told me to always pull the key and lock the car. He said just pulling the key still leaves a lot of stuff active, and can drain the battery quickly.
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