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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #1
Hi guys, postponing my rear brake issue for the time being…
Went out to my car last night and it was totally dead. Like no interior lights when I opened the door dead. Got nothing when I turned the key. It had been sitting for about two weeks. Voltmeter shows almost zero volts at the battery. Put my old trickle charger on a few minutes ago, fingers crossed. It's one of the those Battery Tender charger devices. Charger manual says it can't charge a battery with less than 3 volts. Will check in the morning.

1) If the trickle charger doesn't work, should I jump it, given that it's so depleted? Or should I just pull the battery out and replace it? It's a NAPA that should be free to replace under warranty.

2) RE: Possible causes: I don't think I left the door open or any light on. Haven't had any power problems recently, or lights that don't turn off etc. However, the car stereo shop did recently rewire some stuff to deal with a whizzing noise from the stereo. I noticed tonight that the bolt into the negative side terminal was somewhat stripped and perhaps loose, so there might have been a bad ground. Car stereo visit was 3.5 weeks ago. Drove fine about 2 weeks ago. Could the problem be as simple as a bad ground?

Thanks a lot,
Scott
 

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98 DeVille, 97 DeVille d'Elegance
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Battery tender not going to work with completely dead battery. Unhook and charge it. A few using high amp jump starters have ruined electronics.
Start with that bad bolt on battery.
If i leave my 98 sit for 3 weeks battery goes dead...
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #3
Thanks Rodnok. Kind of a rookie here. How should I charge the battery after unhooking it?
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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26,323 Posts
You need a dedicated 12V battery charger. Take it to a parts store. Have them charge and load test it.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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.......... and one reason that attempting to charge a completely dead battery with the car's alternator is a bad idea is because a dead battery "looks" like a total short circuit to ground for the voltage regulator. Bad things happen then.

If the battery is more than 5 years old it's on borrowed time anyway.
 

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'99 Seville STS; '96/7 ETC
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2,393 Posts
I can understand that a bad negative terminal connection might well make starting difficult - but not why it should cause the battery to drain! Am I missing something?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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A series of short drives, poor electrical connection = slowly depleted battery. Due to the constant 15-20 mA parasitic drain in these cars it would kill a marginal battery during that 2 week layup the OP mentioned.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #10
Thanks Sub, I was wondering that myself. Battery is only 8 months old. Still under warranty. Sounds like the smartest play is to just exchange it at NAPA.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Just for reference, a Battery Minder is NOT a "battery charger" in the true sense that one will wake up a dead battery. Battery Minders (Tenders, etc.) are designed to be connected to a good, charged battery in order to keep the battery at full charge without boiling off electrolyte while preventing plate sulfation. A Battery Minder always holds a battery at about 13.3 volts with an absolute minimal amperage rate - a few mA to equal the car's residual draw. A fully charged battery should read 12.6 volts, disconnected from anything and completely idle for at least a half hour.

Yes, some Battery Minders will output about 3A for a while, but that's only to "top off" a charged battery; then the minder ramps down voltage and amperage to the maintenance rates. You can leave one connected/plugged in indefinitely; you can NOT do that with an old style ferroresonant charger: It will kill the battery overnight - guaranteed. (and there's a world of difference between automotive everyday and "deep cycle" lead-acid batteries.)
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #12
Change of plan. Just dropped the dead battery off at a garage to charge. If it holds a charge and the car starts tomorrow...

1) How can I check the battery for damage due to total depletion? I only have a basic multimeter.
2) How do I confirm that the bad ground was the cause of the dead battery? Test the battery voltage across the terminals with alternator running (should be at around 13-14 volts, right?) and then test after sitting a few hours (should be close to 12.6 volts, right?)

Thanks!
Scott

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p.s. Should the garage be able to tell if the battery is damaged after charging? Don't know what basic equipment can do.
 

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98 DeVille, 97 DeVille d'Elegance
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After charging they should load test the battery, it will if battery is good. Cannot rely upon voltage only. Any decent shop has a load tester.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #14
Okay, thanks. If it checks out with the load test, how do I confirm I've solved the drain problem in the car?
 

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'99 Seville STS; '96/7 ETC
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Aaah, now I understand - I think. The poor connection causes poor charging, not directly an accelerated discharge rate - right?
 

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98 DeVille, 97 DeVille d'Elegance
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Aaah, now I understand - I think. The poor connection causes poor charging, not directly an accelerated discharge rate - right?
It can yes, it may charge just enough to keep warning lights away but not properly charge allowing a quick discharge, also the battery is a key component in the electrical system and a dead battery can cause running issues(doesn't make sense does it but it does).
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Think of an automotive "battery" as a system shock absorber - other than initial engine starting ability it does nothing but "cushion" electrical system surges and depletions due to load changes.
 

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1985 Eldorado Biarritz Convertible, Sable Black, HT4100
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Discussion Starter #19
Hi guys,
Took the dead battery to a garage, got it charged and load tested (so they said, anyway). Voltmeter showed more than 12V. So I put it back in, started the car and drove it for about 20 minutes. No problems, started right up. With the car running, battery showed 14.3v, with car off after drive, showed 12.9v. Seems good. Ran the car diagnostic test, got 52 code for "ECM Memory Reset Indicator," which I think is normal. Cleared it, didn't come back.

Should I just check the battery voltage periodically and see if it dips from high 12v? And if it doesn't dip, should I be good?

Thanks again.
Scott
 
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