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12-18-2010, 07:02 PM
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CC Member
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Join Date: Apr 2007
Cobra Make, Engine: # 757 ERA 427 SC , 482 Al. big block
Posts: 897
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Not Ranked
Charles ... when I was traveling heavily , I used to leave my truck in the garage for a week or two at a time without starting it ( had a company car ) and never had any battery problems . Then I started having some cranking problems and finally a dead battery . Started leaving it on a Battery Tender when I was gone , but had to replace it after a little over 2 years . Long story short .... the new cars today always have a small drain due to all the computer/electronic circuits etc ( theft alarms etc ) to let them keep their presets etc, according to the tech at the Ford dealer . Could that be what is happening and it becomes more of a factor in colder weather as your battery ages ?
As a battery ages , the plates sulfate up some . When it isn`t being kept full charge , that means the plates will sulfate that more quickly and then the battery won`t take a charge like it used to do and it goes downhill even quicker . I have a battery in my Galaxie that is a replica of an old tar top and has been kept on a Battery Tender its whole life and it`s almost 7 years old now ..... hope I didn`t just jinx myself . Why you didn`t have a problem with the 5 year old one , I don`t know .
Bob
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12-18-2010, 07:12 PM
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CC Member
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Join Date: Sep 2002
Cobra Make, Engine: SPF#0760
Posts: 3,409
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Not Ranked
at 80 Degrees F
A fully charged battery (100%) will show 12.68V
12.24V at 50% charge
12.06V at 25% charge
Adgust these V #s by 0.04V for every 10 degrees colder temp
At 30 degrees a fully charged battery should show 12.588V
14.6 or 14.7 is fine for the charging system...
Have the battery checked with a load tester...
Blas
__________________
Wiring Diagrams: SPF MKII, MKIII, GT40, CSX7000, CSX8000, Corvette Grand Sport, and Shelby Sebring, Bondurant & Cinema Tribute Cars.
Owner’s Manuals: SPF MKII, CSX7000, CSX8000, Sebring, Bondurant, Cinema Tribute Cars $ GT40’s..
Large, easy to read and trace schematics with part numbers, wire colors, wire gauge, fuses, and electrical upgrade information. Trouble-shooting and replacement part numbers for those roadside repair adventures.
SPFWiringDiagrams@Comcast.net
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12-22-2010, 09:20 AM
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CC Member
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Join Date: Oct 2003
Posts: 4,078
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Quote:
Originally Posted by Blas
at 80 Degrees F
A fully charged battery (100%) will show 12.68V
12.24V at 50% charge
12.06V at 25% charge
Adgust these V #s by 0.04V for every 10 degrees colder temp
At 30 degrees a fully charged battery should show 12.588V
14.6 or 14.7 is fine for the charging system...
Have the battery checked with a load tester...
Blas
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Blas,
I must be missing something:
Using the figures above and your formula, I get 12.48V at 30 deg F.
.04 x 5 (50 degrees colder than the 80 degree value)= .2V.
12.68V (the 80 degree full charge value) - .2V= 12.48V
How do you get 12.588V for the 30 degree value?
__________________
Chas.
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12-22-2010, 03:54 PM
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CC Member
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Join Date: Sep 2002
Cobra Make, Engine: SPF#0760
Posts: 3,409
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Opps...a typo
~0.01v per 10 degrees...approximately...
All numbers taken from a battery/charging service article…
__________________
Wiring Diagrams: SPF MKII, MKIII, GT40, CSX7000, CSX8000, Corvette Grand Sport, and Shelby Sebring, Bondurant & Cinema Tribute Cars.
Owner’s Manuals: SPF MKII, CSX7000, CSX8000, Sebring, Bondurant, Cinema Tribute Cars $ GT40’s..
Large, easy to read and trace schematics with part numbers, wire colors, wire gauge, fuses, and electrical upgrade information. Trouble-shooting and replacement part numbers for those roadside repair adventures.
SPFWiringDiagrams@Comcast.net
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12-22-2010, 05:22 PM
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CC Member
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Join Date: Oct 2003
Posts: 4,078
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Quote:
Originally Posted by Blas
Opps...a typo
~0.01v per 10 degrees...approximately...
All numbers taken from a battery/charging service article…
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Blas, thanks for the correction-makes more sense now.
__________________
Chas.
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12-22-2010, 03:55 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,025
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Not Ranked
Quote:
Originally Posted by ERA Chas
How do you get 12.588V for the 30 degree value?
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Chas & Blas, I don't think that's right. A lower temperature will increase battery voltage. Full-charge voltage on a 12-volt battery is 0.9 volts higher at 32°F than at 70°F.
Source: https://azsolarutility.com/Battery_Information.html |
12-22-2010, 04:08 PM
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CC Member
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Join Date: Sep 2002
Cobra Make, Engine: SPF#0760
Posts: 3,409
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"...A lower temperature will increase battery voltage..."
Not on the planet I live on... 
__________________
Wiring Diagrams: SPF MKII, MKIII, GT40, CSX7000, CSX8000, Corvette Grand Sport, and Shelby Sebring, Bondurant & Cinema Tribute Cars.
Owner’s Manuals: SPF MKII, CSX7000, CSX8000, Sebring, Bondurant, Cinema Tribute Cars $ GT40’s..
Large, easy to read and trace schematics with part numbers, wire colors, wire gauge, fuses, and electrical upgrade information. Trouble-shooting and replacement part numbers for those roadside repair adventures.
SPFWiringDiagrams@Comcast.net
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12-22-2010, 04:12 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,025
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Quote:
Originally Posted by Blas
"...A lower temperature will increase battery voltage..."
Not on the planet I live on...
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The voltage increases as the temp goes down, but the capacity decreases. Here's another chart that shows the fully charged voltage ratings for 12v batteries at various temperatures. It increases as the temperature declines. http://www.powerstream.com/SLA.htm |
12-22-2010, 04:56 PM
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CC Member
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Join Date: Feb 2008
Location: Jacksonville,
FL
Cobra Make, Engine: Kirkham #570 w Shelby FE
Posts: 1,009
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Unless your running EFI or have a stereo you should have only a couple circuits not cut off by the ignition. The "keep alive" memory for a computer (EFI) or the stereo will typically be less than 1ma (1/1000A). (leaking ign. switch is possible)
As stated, a leak at the alternator or regulator, starter solenoid, lights. While monitoring the battery voltage, pull fuses and disconnect the alt big lead. You should notice a couple tenths of a volt jump when you interrupt the leaking circuit.
Most DMM's have a 200ma current scale and usually a 10A scale, start with the 10A and work your way down. (placed in series with battery cable)
The big thing about batteries is the Amp/hours rating (not the CCA rating which is marketing BS for the most part). Typical car battery is in the 85 ~ 100 A/hr range: (1 amp for 100 hrs, 10A for 10 hrs, 100A for 1 hr.... You get the idea).
You'll probably find a leak of .5~2A from what your describing.
Worst thing they ever did was move from ampmeters to voltmeters on cars. (but hey, 12ft of 10ga copper wire is darn near $5!!) 
Last edited by Ronbo; 12-22-2010 at 05:03 PM..
Reason: afterthought
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12-22-2010, 05:18 PM
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CC Member
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Join Date: Feb 2008
Location: Jacksonville,
FL
Cobra Make, Engine: Kirkham #570 w Shelby FE
Posts: 1,009
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Quote:
Originally Posted by patrickt
The voltage increases as the temp goes down, but the capacity decreases. Here's another chart that shows the fully charged voltage ratings for 12v batteries at various temperatures. It increases as the temperature declines. http://www.powerstream.com/SLA.htm |
Patrick those are charging voltages, not battery idle voltages (which will drop with temp.).
Both voltage and current will drop with temp (capacity in A/hrs). Or power if you will (IxE=P) If E (voltage) went up this would negate the decrease in current (I).
I'm sure we're all aware what effect that first freezing night has on that 5yr old battery we were going to change out. |
12-22-2010, 05:26 PM
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CC Member
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Join Date: Oct 2003
Posts: 4,078
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Quote:
Originally Posted by patrickt
The voltage increases as the temp goes down, but the capacity decreases. Here's another chart that shows the fully charged voltage ratings for 12v batteries at various temperatures. It increases as the temperature declines. http://www.powerstream.com/SLA.htm |
Copied from your link:
While charging, a lower temperature will increase battery voltage. Full-charge voltage on a 12-volt battery is 0.9 volts higher at 32°F than at 70°F. While discharging, a higher temperature will increase battery voltage.
Emphasis is mine. As Ronbo says also, those are while charging and discharging.
But thanks to all for clarifying.
__________________
Chas.
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