Battery dies after sitting for only 10-12 hours - Subaru Outback - Subaru Outback Forums
 
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post #1 of 9 (permalink) Old 07-07-2009, 10:26 AM Thread Starter
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Battery dies after sitting for only 10-14 hours

New to the forum...I'm actually driving my mom's '00 Outback for the summer. Anyhow, I've searched the forum and it sounds like a parasitic drain is fairly common, however, all the posts I saw related to a dead battery after the car was left sitting for a week or more.

So, story is that the car has been driving fine for a month and when I went to leave work a few days ago the car wouldn't start (after sitting from 8am til 5pm). Jumped it off and drove home fine then it wouldn't start the next morning. Took it to Napa to check the battery and it had 12.09 volts when turned off. Dropped it off at the mechanic near work in the morning for them to charge it up (my mistake was not checking the voltage after they charged it). Car was fine when I left to go home from work that afternoon, but was dead the next morning. I was getting 13-14 volts at idle so I figured it was the battery. Purchased a new battery yesterday morning and it was fine the whole day then...yep...it was dead this morning. Any thoughts?

I've had alternator problems on cars before, but the symptom of that was that the car died while driving...this time the car runs fine while driving. As a note, yesterday before I bought the new battery, the ABS light was on / off intermittently after jumping the car and on the way to work after buying the battery. But it has stayed off since I parked it at work yesterday, so I chalked it up to the car just needing to sort itself out after getting a new battery.

TIA for any help! Art
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post #2 of 9 (permalink) Old 07-07-2009, 06:03 PM
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Welcome to the forum.

A new, fully charged battery draining overnight -- that's quite a drain. Are you sure the Parking Light switch (the one on top of the steering column) is OFF? The parking lights themselves can drain several Amps.

A typical car battery might have a 50 Ah capacity. Disregarding some of the more intricate technicalities of these specs, if the battery drains down in 10 hours, that means there's a continuous load of about 5 Amps when the car is parked. The normal "parasitic" drain should be in the range of 0.15 Amps.

If it's not the parking light switch, you might want to make have the charging system tested. While in the car, with a fully charged battery, the alternator should be running at 14-14.8 Volts at 1500 rpm. It's possible that even though you measured 13-14 Volts at idle, the alternator is not actually putting out sufficient current to maintain the charge on the the battery. So at the end of the day, the battery is already significantly discharged.

Other possibilities are corroded connectors at the battery or alternator preventing the battery from being charged.
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post #3 of 9 (permalink) Old 07-07-2009, 07:15 PM
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Sounds like the virgin switch is on (parking light switch as mentioned above).


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post #4 of 9 (permalink) Old 07-07-2009, 08:10 PM
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Could also be a slipping alternator drive belt.

Just noticed that in another thread, ( 04 Outback with A/C problem ) you report that the A/C belt on this car appears to be slipping. Perhaps the same is happening with the belt for the alternator.
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post #5 of 9 (permalink) Old 07-07-2009, 08:13 PM
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Quote:
Originally posted by plain OM
While in the car, with a fully charged battery, the alternator should be running at 14-14.8 Volts at 1500 rpm. It's possible that even though you measured 13-14 Volts at idle, the alternator is not actually putting out sufficient current to maintain the charge on the the battery.
another thing to check would be the output voltage of the alternator with all the accessories on (radio, blower fan, high beams... etc)


... i've seen alternators pass the test unloaded but fail once you turn a couple things on.

make sure its not something simple like the light under the hood sticking on.

Mike
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post #6 of 9 (permalink) Old 07-08-2009, 03:41 PM Thread Starter
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Thanks for the replies. The virgin light was off, checked that. The outcome was an alternator going down hill...under load it wasn't keeping up like two of you mentioned. When I jumped the car off yesterday to go to get the system checked I didn't get a mile down the road before the car began to try and shut off, first time that'd happend (on this car, I've been through 4 alternators on past cars). Since the car had never tried to shut off on me while driving, I didn't think the alternator was the problem...turns out I just had to be patient. Also, Plain OM, I replaced the AC belt while everything was apart so hopefully that will fix the AC problem at highway speed...the other drive belt looked fine.
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post #7 of 9 (permalink) Old 07-08-2009, 03:48 PM
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Quote:
Originally posted by poontz13
Thanks for the replies. The virgin light was off, checked that. The outcome was an alternator going down hill...under load it wasn't keeping up like two of you mentioned. When I jumped the car off yesterday to go to get the system checked I didn't get a mile down the road before the car began to try and shut off, first time that'd happend (on this car, I've been through 4 alternators on past cars). Since the car had never tried to shut off on me while driving, I didn't think the alternator was the problem...turns out I just had to be patient. Also, Plain OM, I replaced the AC belt while everything was apart so hopefully that will fix the AC problem at highway speed...the other drive belt looked fine.
Have any of those ALt's been from subaru. Blu went through 4 of them till he got one from subaru, and it solved the porblem. Aftermarket alts seem to be crap for these cars.

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post #8 of 9 (permalink) Old 07-08-2009, 03:55 PM
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Check your connections. I've had problems with a bad connection draining a battery somehow.

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post #9 of 9 (permalink) Old 07-09-2009, 09:34 AM Thread Starter
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Originally posted by nipper


Have any of those ALt's been from subaru. Blu went through 4 of them till he got one from subaru, and it solved the porblem. Aftermarket alts seem to be crap for these cars.

nipper
Those weren't on a subaru, three were on a Nissan and one on an Audi. By the third one on that nissan I could replace the alt in 30 minutes...
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