On 7 May 2007 09:54:11 -0700, Frank wrote:

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 ?

Not me, but I haven't been measuring lately. See further down.

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.

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.

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.

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.