Battery Voltage Being Too High ?

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Hello:
Have been buying a bunch of those standard 9V batteries (a few different brands) over the past few months, and have noticed that instead of 9V they have been measuring out, with a VOM, at around 10.0 to 10.25. This is under no load.
Anyone else notice this ?
Was wondering if this might be the cause of all the problems I've been having with my fire alarms giving 3 to 4 chirps, around once a day ?
It's probably the same type of chirp signal that the unit gives when the batteries are low.
Thanks, Bob
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I doubt thats it, under load the voltage drops fast,
Have you blown the fire alarms out with compressed air....
They might be overheating
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Don't believe voltage changes with load. Amperage is number to deteriorate. Electromotive potential determines voltage. If you open up a standard 9 volt battery you will find 6 1.5 volt batteries in series. Battery's voltage will depend on materials it is made from. Alkaline batteries will vary from the standard 1.5 volts of old carbon/zinc batteries.
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wrote:

You're kidding right? Amperage goes up with load. Amperage IS load. Where capacity is limited, no load voltage will always be higher than loaded voltage. Amperage goes down with resistance; is that what you meant?

If you open up a battery you will find cells. That is the definition of a battery; a group of cells. I expect there are instances where you would find batteries in batteries, but that would be unusual.
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Capacity is always limited. Voltage only stays constant with load with voltage regulated supplies that are not loaded to capacity.
To "load" something means to increase the current flowing through it. Amperage does indeed go up with load (usually).
Put a volt meter across your 12V car battery. If it reads 12V, your battery is "dead" and probably won't start the engine. An open circuit car battery in good condition that hasn't been recently charged will have ~12.6 V. across the terminals.
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I was trying to address the battery chemistry itself. Available voltage depends on the cell potential, i.e. the redox chemistry of the chemical electrodes. The best you can do with chemicals is about 6 volts. This is why you need cells in series.
There is a concentration dependence which accounts for voltage drop with time. But amperage is dependent on the total concentration of ingredients. You look at it like water pressure through large and small pipes. At equal pressure, you're going to get a lot more water through the big pipe. That's amperage. If all you needed was voltage, then you could replace the big lead acid battery in your car with eight triple A rechargeable batteries.
That said, I put my VOM to a new 9 volt alkaline battery and it measured 9 volts. Did not leave it hooked up to see how long that would last. I did note that a lot of newer rechargeable batteries are less than the voltage of the batteries they replace. Most modern stuff will handle them.
Frank
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I agree with you in principle but I've come to accept the fact that definitions evolve and words mean what people want them to mean. Thus (and unfortunately) it has become acceptable to refer to a single power cell as a battery.
One would hope, however, that when the apparently indivisible (to a layperson) unit is indeed composed of several sub-units (and by this I mean car batteries, 9V batteries, etc.) we might at least in this instance continue to refer to the sub-units as cells and not batteries within batteries!
But it's an unwinnable war. Someday I fully expect the term "it's" to become fully acceptable in standard English in the possessive sense and then the barbarians will have won. In the meantime I wish web forum software would come with a plug-in that would, on displaying posted text, randomly convert "it's" into "it is". Correct users will still be correct if a bit stilted. Incorrect users will be made to look moronic.
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That was pretty much my point. I don't take issue with D-cells being called batteries.
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Steve Kraus wrote:

To each hi's own.
--
Postulate a God who\'s so smart He designed things we won\'t discover for the
next ten years, but who\'s so incredibly stupid He couldn\'t think up the
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That is not always true. For example:
It's come to my attention that. . .
In this case "It's" means "It has"
--
I don\'t understand why they make gourmet cat foods. I have
known many cats in my life and none of them were gourmets.
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Don't believe you've ever checked that with a voltmeter... or read Ohm's Law, either.

Incorrect -- voltage drops across a load. That's pretty basic circuit theory.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On 7 May 2007 09:54:11 -0700, Frank wrote:
Because a battery has an internal resistance, when placed in a circuit with a load, it's effective (which is what you will measure with a meter) voltage will drop.
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wrote:

Battery voltage is only "nominal" or approximate. An old type battery, a carbon/zinc was nominally rated at 1.5 volts but actually under no load put out 1.7 volts, other types will vary. A car lead/acid battery actually puts out 2.2 volts per cell. When cars used 6 volt batteries they used 3 cells which actually gave 6.6 volts or a nominal 6 volts. Today's car batteries out a nominal 12 volts which is actually 14.2 volts.
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Frank wrote: ...

Since the battery has resistance as the load increases the voltage will drop. If the battery had no resistance you would be correct.
My guess is the OP is using a digital meter and is finding he gets different results since the resistance of the meter is so much higher than the old analog meters. Of course part of the problem is likely to be as you correctly pointed out the measured voltage of different kinds of batteries varies.

--
Joseph Meehan

Dia \'s Muire duit
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That would be an IDEAL voltage source (and, of course, ideal things aren't).
A REAL voltage source behaves as an ideal voltage source in series with a resistor. This resistance (the cell resistance, not a separate component) is in series with the load. In this way, voltage at the battery terminals will vary with load. As the battery discharges, its internal resistance increases, causing a greater voltage drop when a load is applied.

Not "determines", "is". "Voltage" is a name for electromotive potential. This explains the use of the symbol 'E' for voltage.

True of fully charged cells with no load, although the numbers ARE approximate.
--
Mark Lloyd
http://notstupid.laughingsquid.com
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Not me, but I haven't been measuring lately. See further down.

Batteries themselves have internal resistance. I suppose, if you measure the amperage in the circuit, and you measure the difference in battery voltage with no current, and the battery voltage with that amperage, you can find the voltage drop and calculate the internal resistance. Although I'm not sure if it constant at all current levels.

Different chemical reactions create different voltages. There are chemical reactions at both poles of a cell, and the sum of the two voltages with carbon-zinc batteries is about 1.5. When they wanted to make other kinds of batteries, that would be the same size and work in the same devices that carbon-zinc batteries did, they tried to come up with pairs of reactions that would also total 1.5 or close.
I'm wondering if the batteries that Robert1 has might have been made with different from the normal chemicals, to save money I suppose, and that is why their voltage is so high. Sort of like some Chinese manufacturer put melamine in dog food to raise the apparent protein content. (Because melamine has some ingredient that increases some measurement on tests.)
R, you say a bunch of different brands. Does that include name brands? What brands? Lots of off brands are made by the same company. Even name brands can be forged, or some manager might do something to make extra for himself.
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Frank wrote:

Hmmm., Trying to reinvent Ohm's law?
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I've found that voltage reduces as load (amperage usage) increases.
--

Christopher A. Young
You can\'t shout down a troll.
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snipped-for-privacy@aol.com wrote:

OVERHEATING????? Geez from what hollerbutt?
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wrote:

A battery cell is a chemical cell. The voltage generated varies with the chemical concentrations and will decrease gradually from its peak voltage until it is near chemically exhausted at which time there will be a sharper drop. At exhaustion there will be chemical reaction products that cause corrosion. The devices you use should be able to operate at plus or minus 2 volts of the 9 volt nominal rating.
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