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  #1  
Old 05-06-2009, 08:25 AM
bordelond bordelond is offline
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Can a dead alternator drain a brand-new battery with a day or two?

Long story short -- new battery installed in wife's car Monday evening. Car's been started 7 or 8 times since, started up like a champ each time. This morning, I'm at work and my wife claims car won't start and "battery light is beeping". She held her phone up to the instrument panel, and something is/was beeping. It's absolutely confirmed that no lights, radio, etc. were left on overnight -- nothing like that is the issue.

Father-in-law passed by my house and looked at wife's car's battery, declared it to be dead and blamed the alternator as the likely culprit. I have not talked to my FIL, getting this second hand from my wife.

FWIW, it's a 2003 Ford Taurus. Anybody ever run into a similar issue? TIA for any advice.
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  #2  
Old 05-06-2009, 08:26 AM
Philster Philster is offline
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Yes.

Common.

The battery is still ok. If you get the alternator replaced (the most likely culprit) and charge the battery, you should be good to go. Again, this is common, but not always the issue. Gotta start with the likely things first. A decent shop should be able to check the alternator and confirm.

Last edited by Philster; 05-06-2009 at 08:28 AM..
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  #3  
Old 05-06-2009, 08:33 AM
Rick Rick is offline
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Your FIL is correct the alternator is the most likely culprit. Not the only one mind you, but the most likely.
You can either:
  1. Throw parts at it
  2. Pay someone to check it out and throw the right part at it the first time
  3. Check it out yourself (assuming you have a voltmeter) and throw the correct part at it.
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  #4  
Old 05-06-2009, 09:33 AM
muldoonthief muldoonthief is offline
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And just to expand on things -

The alternator is basically a generator which converts the mechanical energy of the engine into electrical energy. This electrical energy is used for lots of things in the car - powering the spark plugs, keeping the various lights lit, powering the radio, and charging the battery. When the alternator is running correctly, the battery is doing nothing to power the car, and can in fact be disconnected without the car dying. In this normal domain of operation, the battery is only needed for starting the car - the electrical energy of the battery is used to start the mechanical parts of the engine moving, and to power the spark plugs. Once the engine starts running, the alternator takes over again.

If the alternator is dead, but the battery is fully charged, the car can and does use the electrical energy provided by the battery to run all the electrical requirements of the car. However, the battery is now being drained the entire time the car is running, and there's nothing going to recharge it. You can often notice this happening because the lights begin to dim in the car as the battery discharges.

It can happen where the battery has enough power to continue running the car, but after it's been turned off for a while, it doesn't have enough power to start the car again. This happens for 2 reasons - the power required to start the car is much higher than what's required to keep it running, since you're using electrical energy to get big pieces of metal in motion, and there's usually a small current flow even when the car is turned off for things like the radio memory, remote key fob receiver, alarm systems, etc.
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  #5  
Old 05-06-2009, 09:45 AM
Gary T Gary T is offline
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Quote:
Originally Posted by muldoonthief View Post
When the alternator is running correctly, the battery is doing nothing to power the car, and [the battery] can in fact be disconnected without the car dying.
True, and it can ruin the alternator or certain electronic devices to do so. It's not 1960 anymore, and we don't have DC generators on cars (that's when it was safe to do this). Do yourself a favor, everyone, and DO NOT run the engine with the battery disconnected.

Last edited by Gary T; 05-06-2009 at 09:46 AM..
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  #6  
Old 05-06-2009, 09:49 AM
muldoonthief muldoonthief is offline
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Quote:
Originally Posted by Gary T View Post
True, and it can ruin the alternator or certain electronic devices to do so. It's not 1960 anymore, and we don't have DC generators on cars (that's when it was safe to do this). Do yourself a favor, everyone, and DO NOT run the engine with the battery disconnected.
Whoops, sorry - I posted that as information, not advice.
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  #7  
Old 05-06-2009, 09:52 AM
bordelond bordelond is offline
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Thanks for the responses, all. You guys confirmed our suspicions. Off to the shop.
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  #8  
Old 05-06-2009, 09:53 AM
Gary T Gary T is offline
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The problem could be an alternator that's not charging, or it could be an electrical drain on the battery. And as Rick said, you can either have it diagnosed by testing, and have confidence that the indicated repair will fix it, or you can diagnose by parts replacement, where if your first guess is right it will save you money but if you guess wrong it can get very expensive.
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  #9  
Old 05-06-2009, 10:07 AM
bordelond bordelond is offline
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Quote:
Originally Posted by Gary T View Post
The problem could be an alternator that's not charging, or it could be an electrical drain on the battery.
The shop will test the charging system, but ... what kind of an electrical drain could conceivably kill a battery that quickly?
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  #10  
Old 05-06-2009, 10:21 AM
Philster Philster is offline
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Starting the engine....providing thousands and thousands of sparks once running...not to mention the electronics of the car.

Last edited by Philster; 05-06-2009 at 10:22 AM..
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  #11  
Old 05-06-2009, 10:49 AM
Gary T Gary T is offline
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Quote:
Originally Posted by bordelond View Post
... what kind of an electrical drain could conceivably kill a battery that quickly?
An internal short in the alternator or a stuck relay that allows a significant power consumer to stay on are the first two that come to mind.
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  #12  
Old 05-06-2009, 11:23 AM
bordelond bordelond is offline
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Quote:
Originally Posted by Philster View Post
Starting the engine....providing thousands and thousands of sparks once running...not to mention the electronics of the car.


Doesn't that equal "bad alternator"?

Put another way -- assuming a brand-new fully-functional alternator and a brand-new fully-charged battery (I understand some are sold undercharged when new). No lights left on, no electronics left on. The alternator and battery both pass diagnostics by three different super-reputable shops with flying colors.

Given all that ... is there something that could conceivably kill a battery in less than two days of light driving?

GaryT mentions a stuck relay, for instance.
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  #13  
Old 05-06-2009, 11:25 AM
Really Not All That Bright Really Not All That Bright is offline
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How does a light beep?
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  #14  
Old 05-06-2009, 11:30 AM
bordelond bordelond is offline
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Quote:
Originally Posted by Really Not All That Bright View Post
How does a light beep?


Dunno.
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  #15  
Old 05-06-2009, 12:33 PM
Harmonious Discord Harmonious Discord is offline
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Quote:
Originally Posted by Really Not All That Bright View Post
How does a light beep?
A driver with Synaesthesia.
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  #16  
Old 05-06-2009, 06:24 PM
Fubaya Fubaya is offline
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Quote:
Originally Posted by bordelond View Post
Put another way -- assuming a brand-new fully-functional alternator and a brand-new fully-charged battery (I understand some are sold undercharged when new). No lights left on, no electronics left on. The alternator and battery both pass diagnostics by three different super-reputable shops with flying colors.

Given all that ... is there something that could conceivably kill a battery in less than two days of light driving?
The alternator charges the battery, so if the alternator and battery are good, nothing will kill the battery*. If the alternator is bad, then everything electrical is running off the battery and it doesn't take much to drain it. Just starting the car a few times may do it.

Ok, some things can but I don't suppose your wife has a winch that draws 400 amps on her Taurus.
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  #17  
Old 05-06-2009, 08:47 PM
Gary T Gary T is offline
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Quote:
Originally Posted by Fubaya View Post
The alternator charges the battery, so if the alternator and battery are good, nothing will kill the battery*.... Ok, some things can but I don't suppose your wife has a winch that draws 400 amps on her Taurus.
No, but it has headlights that draw 10 amps, and they can drain the battery enough to cause a no start in a matter of hours. There are a number of things that could cause a drain big enough to cause a no start from sitting overnight.
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  #18  
Old 05-06-2009, 08:56 PM
Fubaya Fubaya is offline
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Originally Posted by Gary T View Post
No, but it has headlights that draw 10 amps, and they can drain the battery enough to cause a no start in a matter of hours. There are a number of things that could cause a drain big enough to cause a no start from sitting overnight.
But he said "brand-new fully-functional alternator and a brand-new fully-charged battery (I understand some are sold undercharged when new). No lights left on, no electronics left on."
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  #19  
Old 05-06-2009, 09:52 PM
Rick Rick is offline
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A sticking relay, a computer that does not shut down, a trunk light that stay on can all drain a battery overnight.
I once had a car that would drain the battery night after night. I tested for a draw every way I knew how. NO draw, but the next morning the battery was dead.
After a hour or two of exhausting every possibility I was standing next to the car looking at the parking place outside where it had gone dead the night before, and I asked myself the question "What is different out there, than in the shop here?"
I came up with:
  1. One is outside, one is inside
  2. windows rolled up
  3. door locked
I eliminated #1 out of hand. I rolled up the windows to test #2, nothing.
Then I locked the car, and found the lock relay was sticking causing a 10 amp draw.
The bottom line is this:
Either the battery is in fact bad, the alternator is in fact bad, or there is a draw. There is no fourth choice.
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  #20  
Old 05-06-2009, 10:11 PM
Fubaya Fubaya is offline
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I guess I misread it as "the electrical system is perfect, can it still go dead?"
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  #21  
Old 05-06-2009, 11:46 PM
Gary T Gary T is offline
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Quote:
Originally Posted by Fubaya View Post
[But he said...] "No lights left on, no electronics left on."
...That he knows about. Left on (accidentally not shut off by the operator) is one thing. Stuck on (through no fault of the operator, and often not detectable by the operator) is quite another. He was sure that nothing was left on, and I'll grant that. But unless he tested the drain on the battery with an ammeter, he cannot be sure that nothing was stuck on.

There are several possible malfunctions that can cause a significant drain on a battery, to the point of rendering it unable to crank the starter after one or two overnights. And some of those malfunctions are not evident and give no clue that they even exist until the battery is found dead, and it cannot be determined whether or not they exist without measuring battery drain with an ammeter.

One example: a body control module that draws, say, 350 milliamps until it goes into "sleep" mode, which it should do an hour after the ignition is shut off. In sleep mode it might draw 10 mA. Other parasitic drains (computer memories, radio memory, etc.) add up to maybe 25 mA. So normal parasitic drain is 35 mA, but if that module fails to go to sleep then the drain is 375 mA, over ten times normal. I don't know of any way to tell whether the module has gone to sleep or not, or whether the drain is 35 mA or is 375 mA, other than measuring with an ammeter. The first (and only) clue the driver would get is a dead battery.

I'm not saying this type of problem is likely, just that it is possible, and has indeed been known to occur.

Last edited by Gary T; 05-06-2009 at 11:51 PM..
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  #22  
Old 05-06-2009, 11:59 PM
elfkin477 elfkin477 is offline
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Maybe this is a dumb question, but did you check to make sure the battery's connections are tight enough? The last time I bought a brand new battery my car wouldn't start on day 3, and it turned out that a too-loose connection was joustled even looser, so there wasn't enough contact. I fixed the issue by tightening the bolt on the clamp with a ratchet and had no more problems.

Last edited by elfkin477; 05-06-2009 at 11:59 PM..
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  #23  
Old 05-07-2009, 08:45 AM
bordelond bordelond is offline
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Quote:
Originally Posted by Rick View Post
Either the battery is in fact bad, the alternator is in fact bad, or there is a draw. There is no fourth choice.
Update:

AFAIK, it turned out that the battery was, in fact, bad. It only tested out at 258 cold-cranking amps (CCA) ... was supposed to be 650 CCA when new. Alternator was tested and checked out fine.

However ... after reading the later replies to this thread, it appears that some kind of "phantom" electrical draw can't be ruled out. Might take the car back to the shop after work and ask for a quick battery test (the battery I bought Monday night was replaced with another new one, not recharged) to see if the new-new battery's CCA look unusually low. If the CCAs are low, then I guess it'll be time to break out the ammeter.

...

Slight digression -- I bought the Monday-night battery from a big-box auto supply store. After my shop tested their battery and found it to be nearly dead, I went to Big Box to get a full refund. Big Box tested the battery also, found it nearly dead (I was standing right in front of the tester and saw the REPLACE BATTERY message on the little green screen). Big Box tested the battery twice more, and got the same result twice more.

Since my shop installed another new battery yesterday afternoon, I wanted a refund on the apparently bad battery Big Box sold me on Monday. Big Box refused -- instead of a refund, they offered to either recharge the bad battery or replace it with another new one. Does that sound like business as usual? I am taking it to Bix Box corporate above the individual-store level ... just didn't expect to get any resistance at all (yes, I have all receipts).

Thanks for all the advice and knowledge shared in this thread
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  #24  
Old 05-07-2009, 04:41 PM
Rick Rick is offline
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The testers used now a days give a direct reading of available CCA independent of the state of charge (assuming that the battery is above about 6V)
So if a 650 CCA battery reads 258 it is bad, not discharged.
If it makes you feel any better the last big box auto parts store battery I bought was DOA also. It had been sitting on the shelf too long and was dead.
Recharging a battery that reads replace is an exercise in not knowing what the fuck you are doing. It is the automotive equivalent of taking a cart with a dead horse hitched to it and hitching up another dead horse for greater speed. Needless to say a cart with two dead horses attached is no faster than a cart with one dead horse.

You approach with the big box boys should be something along the lines of
Because you sold me a defective battery I had to take my car to the shop and pay for an electrical system diagnosis. This would not have been necessary if your battery was not defective. The diagnosis turned up no other issues with the electrical system, just your defective battery. Since I needed to get home and since I no longer trusted your merchandise, I purchased a good battery from the shop. This is why I want a refund on your defective battery. I should also ask for the diagnostic fees I paid, but I won't.

Good luck, let us know how it turns out.
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  #25  
Old 05-08-2009, 04:01 PM
bordelond bordelond is offline
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Quote:
Originally Posted by Rick View Post
If it makes you feel any better the last big box auto parts store battery I bought was DOA also. It had been sitting on the shelf too long and was dead.
I've since been told that this is not uncommon.

Quote:
Recharging a battery that reads replace is an exercise in not knowing what the fuck you are doing. It is the automotive equivalent of taking a cart with a dead horse hitched to it and hitching up another dead horse for greater speed. Needless to say a cart with two dead horses attached is no faster than a cart with one dead horse.


I'm a little smarter today, thanks.

Quote:
You approach with the big box boys should be something along the lines of
Because you sold me a defective battery I had to take my car to the shop and pay for an electrical system diagnosis. This would not have been necessary if your battery was not defective. The diagnosis turned up no other issues with the electrical system, just your defective battery. Since I needed to get home and since I no longer trusted your merchandise, I purchased a good battery from the shop. This is why I want a refund on your defective battery. I should also ask for the diagnostic fees I paid, but I won't.

Good luck, let us know how it turns out.
I called Big Box Customer Relations line (which was harder to find online than you'd expect, but find it I did). They took some information from me about the transaction and recommended that I return to the local Big Box to speak with the day manager. The day manager granted my refund nearly summarily, though he did mention something about how the battery manufacturer wouldn't reimburse the store for faulty merchandise. So in the end of it all, I got satisfaction.

Thanks for the advice, everyone.
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  #26  
Old 05-08-2009, 06:08 PM
Spectre of Pithecanthropus Spectre of Pithecanthropus is offline
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This very thing happened to me. I assume my experience is typical: the godawfully vague "Check Engine Soon" light came on, and a couple of hours later all the lights blinked before the battery dropped dead. Of course, the owners manual says you must hie yourself to the dealer when this happens. Of course they would. I'm honestly not too good with cars, but the tech from the Auto Club confirmed my suspicion that it was just the alternator, which of course it turned out to be and not a bad repair bill at all, compared with what's possible.
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