On May 7, 1:12 pm, "Toller" wrote:
"Frank" wrote in message

ps.com...



On May 7, 12:30 pm, " wrote:
On May 7, 12:29?pm, "Robert11" wrote:

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

I doubt thats it, under load the voltage drops fast,

Have you blown the fire alarms out with compressed air....

They might be overheating

Don't believe voltage changes with load. Amperage is number to
deteriorate.

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?

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.

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.

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