Battery Truths
Thread Starter
Le Mans Master
Joined: Jan 2001
Posts: 6,429
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From: Maryville TN
St. Jude Donor '06-13,'16-'17, '19
Battery Truths
Is it true that once a battery goes below 12 volts the battery is junk?
It's been my experience that once a battery will no longer start a car it is a goner no matter the age of the battery. I've never been able to get a battery to hold a charge once it goes bellow 12 volts.
That being said, my 2 year old DieHard just died. Sears tested it and said that it was fine! Pumped a quick charge into it and sent me home.
I don't trust this battery anymore. Should I?
Tom
It's been my experience that once a battery will no longer start a car it is a goner no matter the age of the battery. I've never been able to get a battery to hold a charge once it goes bellow 12 volts.
That being said, my 2 year old DieHard just died. Sears tested it and said that it was fine! Pumped a quick charge into it and sent me home.
I don't trust this battery anymore. Should I?
Tom
Last edited by TCW; Dec 23, 2011 at 05:25 PM.
Race Director
Joined: Aug 2005
Posts: 13,592
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From: Hudson WI
NCM Sinkhole Donor
We make over 100M car batteries a year. I can't talk about cam spec's but batteries I know.
The average flooded battery in a car is not made to take deep discharging. 12 volts is OK, but if you get below 10 you start to damage it. A battery is fully charged at about 13 volts. Unless the battery was discharged for a long period of time at low voltage, I would not worry about it.
The average flooded battery in a car is not made to take deep discharging. 12 volts is OK, but if you get below 10 you start to damage it. A battery is fully charged at about 13 volts. Unless the battery was discharged for a long period of time at low voltage, I would not worry about it.
Advanced
Joined: Jan 2004
Posts: 83
Likes: 3
From: Aiken SC
I purchase non-working riding mowers and fix them up as a hobby. Many times I've picked up a mower with a battery indicating less than 12 volts. An over-night charge on the old trickle-charger brought them back to life. Of course, that's not true all of the time.
I would think a two year old Die Hard would be just fine after a good charging.
I would think a two year old Die Hard would be just fine after a good charging.
Racer
Joined: Oct 2011
Posts: 475
Likes: 3
From: Jacksonville TX
I always try to do a trickle charge on a low or dead battery. I try to stay away from a quick charge. A battery sides that are expanded is normally not a good sign. I have had them last a few years once expanded.
Drifting
Joined: Apr 2006
Posts: 1,276
Likes: 5
From: Ambler Pa.
Is it true that once a battery goes below 12 volts the battery is junk?
It's been my experience that once a battery will no longer start a car it is a goner no matter the age of the battery. I've never been able to get a battery to hold a charge once it goes bellow 12 volts.
That being said, my 2 year old DieHard just died. Sears tested it and said that it was fine! Pumped a quick charge into it and sent me home.
I don't trust this battery anymore. Should I?
Tom
It's been my experience that once a battery will no longer start a car it is a goner no matter the age of the battery. I've never been able to get a battery to hold a charge once it goes bellow 12 volts.
That being said, my 2 year old DieHard just died. Sears tested it and said that it was fine! Pumped a quick charge into it and sent me home.
I don't trust this battery anymore. Should I?
Tom
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,717
From: Springfield MO
To me, convenience is a major factor in my decisions. Finding your battery dead is inconvenient, especially if you are in a motel parking lot on a Sunday morning hundreds of miles from home(even worse if the wife is with you).
For $120, get a new Duralast Gold from AutoZone and then put it out of your mind.
For $120, get a new Duralast Gold from AutoZone and then put it out of your mind.
Pro
Joined: Nov 2001
Posts: 567
Likes: 23
From: Venice Florida
Conventional 12 volt batteries are 2.1 volts per cell when up,( 12.6 volts is charged,12 volts indicates a discharged battery). I agree with the slow charge method with this exception: a battery that is deeply discharged may need a high rate of charge for the 1st hour to overcome the internal resistance, after first hour cut back to 10 amps or less rate of charge.
Thread Starter
Le Mans Master
Joined: Jan 2001
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From: Maryville TN
St. Jude Donor '06-13,'16-'17, '19
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Team Owner
Joined: Sep 1999
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From: Springfield MO
I have one in my supercharged Mercedes(half the price of a M-B battery) and it's been doing great for the past 4 years. I also have them in my 56 and 64 vettes which very seldom get driven(kept on a float charger all the time). They have both been in for around 6 years with no problem. I let the OE Delco batttery die on my 09 Z06(forgot to plug in the float charger after I unplugged it to plug in the air compressor to air tires(my bad)). It charged up, but I'm going to replace it with the Duralast Gold in the Spring, to ward off any potential problems, if it is weakened.
Team Owner
Joined: Sep 1999
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From: Springfield MO
There must be a good reason GM didn't feel that the cheap way to reduce 15 lbs was not cost effective.
Safety Car
Joined: Sep 2006
Posts: 4,759
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From: L.A. aka TooDamnManyPeopleville Ca.
To me, convenience is a major factor in my decisions. Finding your battery dead is inconvenient, especially if you are in a motel parking lot on a Sunday morning hundreds of miles from home(even worse if the wife is with you).
For $120, get a new Duralast Gold from AutoZone and then put it out of your mind.
For $120, get a new Duralast Gold from AutoZone and then put it out of your mind.
Good man! I just installed one of these on Thursday! 
The original was installed in August of '07. I drove it on Sunday and when I came out on Monday it was dead. At first I thought it was the fob battery, because it let me in the car and I was getting a 'no fob' message on the DIC.
The next day I replaced the fob battery and it wouldn't let me in.
So I bought a new battery the next day and it started right up! Turns out that there was a powdery build up on the negative cable that I never saw because of the plastic cover on it. I'll be more vigilant from now on.
Melting Slicks
Joined: Mar 2007
Posts: 2,391
Likes: 23
From: Santa Barbara CA
Is it true that once a battery goes below 12 volts the battery is junk?
It's been my experience that once a battery will no longer start a car it is a goner no matter the age of the battery. I've never been able to get a battery to hold a charge once it goes bellow 12 volts.
That being said, my 2 year old DieHard just died. Sears tested it and said that it was fine! Pumped a quick charge into it and sent me home.
I don't trust this battery anymore. Should I?
Tom
It's been my experience that once a battery will no longer start a car it is a goner no matter the age of the battery. I've never been able to get a battery to hold a charge once it goes bellow 12 volts.
That being said, my 2 year old DieHard just died. Sears tested it and said that it was fine! Pumped a quick charge into it and sent me home.
I don't trust this battery anymore. Should I?
Tom
I guess the real question is "why did it die"? Probably an underlying reason for it, at least based on my experience as a Technician. Sometimes batteries do have a cell fail, and in that case they will only hold about 10.5 volts.
But yes, when a battery gets below 12.0 volts, it has been proven to reduce it's life span and cause early failure. This has been a big issue and some of the OEMs have been putting extra effort into making sure batteries are properly maintained in new cars that are in dealer inventory. Voltage should be kept at 12.5 volts or higher for the best battery life.
For what it's worth, here's a chart of voltage vs. charge % :
12.65 V = 100%
12.45 V = 75%
12.24 V = 50%
12.06 V = 25%
11.89 V = Discharged
My experience and opinion is that once a battery is discharged, it's never 100% again. I'd replace it if I were you, even if that means buying a new one yourself. Then I'd do some amperage draw testing to see if you have something abnormal going on that is causing the battery to drain. If everything checks out normal, get a battery tender to help protect the new battery and maintain proper voltage.
My opinion at least
Safety Car
Joined: May 2011
Posts: 3,582
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From: va
With all the money GM spent to reduce the weight on the Z06(and the extra money the consumer has to spend to purchase a new Z06 over the heavier base/GS C6), and all they had to do is spend another $25 and save 15 lbs using a deka battery, they would have done it in a heartbeat.
There must be a good reason GM didn't feel that the cheap way to reduce 15 lbs was not cost effective.
There must be a good reason GM didn't feel that the cheap way to reduce 15 lbs was not cost effective.
Thread Starter
Le Mans Master
Joined: Jan 2001
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From: Maryville TN
St. Jude Donor '06-13,'16-'17, '19
Tech Contributor
Joined: Oct 1999
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From: Charlotte, NC (formerly Endicott, NY)
Just because it has been completely discharged doesn't mean it is bad. Have had many batteries that I accidentally discharged to the point the horn wouldn't blow and the lights wouldn't light and was able to charge them and use them for years after the discharge. In the old days before we had automatic warning of the headlights being on it was a lot easier to leave the head lights on all day and run a battery completely down.
Bill
Bill
