12 volt power source?

On 12/23/2007 4:16 PM Charles Davis spake thus:


Gawd, I hope not!

Hah. Mine's an '87 Toyota van, and even if it did have anything that would drain the battery it doesn't matter since I disconnect the battery as an anti-theft measure.
12 volt batteries don't get up to 13.8 volts, sorry.
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David Nebenzahl wrote:

Ah, but they do. My '87 Ford F250, while running down the road, will 'float out' at 14 or 14.5 After siting for a while 10 or 20 minutes, the 'voltmeter' reads close to 14 before the starter kicks in.
Of course that's an OEM automotive dashboard gauge. Which I wouldn't guarantee the accuracy of.
Chuck D.
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On 12/23/2007 5:50 PM Charles Davis spake thus:

I'd be curious to see what a decent multimeter makes of the actual voltage of that battery. And by "sitting", you mean engine turned off, right?
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David Nebenzahl wrote:

Probably with the engine running and the battery being charged.
--
Venlig hilsen
Erik Olsen
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Erik Olsen DK wrote:

Nope! "Sitting" = Engine off, no accessories in use, only drain on battery --- 'chemical "self discharge" (What drains a 'charged battery' over long periods of time.)
Chuck D.
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David Nebenzahl wrote:

Yup!!
In the past, when I have been using a 'decent' multimeter on the electrical system, I haven't noticed any great (or even consistent 'minor' differences. Just the difference you would expect comparing readings on a 'multimeter' with a 90deg full range for 15 volts scale, with a dashboard 10 degree for 16 volt scale.)
Chuck D.
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On Sun, 23 Dec 2007 20:50:08 -0500, I said, "Pick a card, any card"

Impossible. Just not true.

LOL. -- Ray
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Ray Haddad wrote:

The steady state voltage of a charged battery is that produced by the electrochemical activities in the individual cells, which create a stable voltage (for a given temperature). That stable voltage per cell is of the order of 2.1 volts, giving 12.6 volts for 6 cells in series - which is why one measures about 12.6V by applying a meter across the terminals without other loads.
It isn't 12 volts or 13.8 volts, it is what the laws of physics and chemistry require it to be.
However when the system is NOT steady state, a range of outcomes is observable. The wikipedia article at http://en.wikipedia.org/wiki/Lead-acid_battery covers some of these situations apparently fairly accurately.
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On Mon, 24 Dec 2007 16:55:59 +1100, Eddie Oliver wrote:

Yeah, well, how do you know what it's doing when you're not looking?
--
Erwins Felix

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On 12/23/2007 11:59 PM Steve Caple spake thus:

... like that goddamned light in the refrigerator: how do you *know* it goes out when you close the door? (That's my poor man's explanation of the Schrdinger paradox).
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David Nebenzahl wrote:

But it is possible to observe if the light in the refrigerator does not go out, allthough indirectly.
We recently had one with a defect door so that the door contact was not activated, hence the light was on all time. This caused the temperature around the lamp to raise enough to make some food items go bad too early, whereas the overall temperature was still kept by the thermostatic control.
--
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Erik Olsen
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On Mon, 24 Dec 2007 00:27:45 -0800, David Nebenzahl wrote:

You mean it's forbidden to just push in the door switch plunger? Or slip oin one of those mini-camera cables SWAT outfits use?
--
Steve

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On 12/24/2007 12:35 PM Steve Caple spake thus:

No, of course not, but you know about the Heisenberg Uncertainty Principle, right? The one that says that any attempt at measurement interferes with the phenomonon being measured? (At least that's my dumb-ass layman's take on it.) So how can you ever *really* be sure that the light is out when the door is closed?
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On Mon, 24 Dec 2007 13:47:57 -0800, David Nebenzahl wrote:

Faith, me lad, sure an begorra, just believe!
--
Steve

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Greg Procter skriver:

http://sealake.manufacturer.globalsources.com/si/6008802449598/pdtl/Sealed-lead-acid/8816217775/12V100Ah-Nominal-Capacity-Rechargeable-Sealed-Lead-Acid-Battery.htm
http://www.electronicsforu.com/efylinux/circuit/feb2003/sept99_chargemonitor.pdf
Both links shows that at constant charger should not be higher than 13,8 volts. None of your links is showing the actual voltage of the battery without a charger.
Klaus
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Modelbane Europas hjemmeside: http://www.modelbaneeuropa.hadsten.dk
Modeltog, internet, gratis spambekmpelse, elektronik og andet:
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"Klaus D. Mikkelsen" wrote:

http://sealake.manufacturer.globalsources.com/si/6008802449598/pdtl/Sealed-lead-acid/8816217775/12V100Ah-Nominal-Capacity-Rechargeable-Sealed-Lead-Acid-Battery.htm
Quote from first reference: "Control voltage: constant voltage 14.5V to 14.9V (per 12V cell 25 degrees Celsius) Float: control voltage: 13.6 to 13.8V (per 12V cell 25 degrees Celsius)"

If one charges a battery to 13.8 volts it will be at 13.8 volts.
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On Mon, 24 Dec 2007 08:18:11 +1300, I said, "Pick a card, any card"

Never. -- Ray
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Ray Haddad wrote:

How precise/pedantic are we being?
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On 12/23/2007 12:41 PM Greg Procter spake thus:

Greg, do us a favor: go out right now (well, assuming it's light outside) and measure your car's battery voltage. Measure a couple if you have more than one. Report your findings back here.
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David Nebenzahl wrote:

David, read the line which I have requoted below:
"If one charges a battery to 13.8 volts it will be at 13.8 volts."
Now before you start with the ifs and buts, think about it. Yes, 24 hours later it will have dropped in voltage to something like 12.5 volts, depending on a whole list of factors; temperature, acid level, ... but it will, if charged to 13.8 volts, stand at 13.8 volts for some time. THAT is the voltage any electrical equipment attached to the battery must be able to withstand.
If you take _your_ battery from your car and power your model railway with it, the voltage available will start at 12.5 volts - not 12 volts - and slowly drop to about 10.5 volts as your train goes round and round. You should have stopped it at 10.8 volts to avoid damaging your battery. 12.5 + 10.5 / 2 = 11.5 volts. You really should get a new stick on label printed for your battery "Exide 11.5 volt battery" rather than the only correct for an instant "Exide 12 volt Battery". (or a whole series of labels with different voltages so you can strip them off one after the other to match the 'Truth in Advertising' requirements)
The safe operating range of a 12 volt car battery is 13.8 - 10.8 volts and the circuit in the car should hold it in a range close at or near to or below 13.8 volts.
It's fun arguing with Ray because he seems to have it in for me, but I'd rather real people like you kept the context in mind when getting involved.
Regards, Greg.P.
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