9 Volt Battery End of Life Voltage

[mediatechnology]

Q: What is the typical end-of-life voltage for a 9V battery?

A: My smoke detector thinks it's ~7.3 volts open-circuit.

At what voltage do wireless mics and stomp boxes typically begin to fail?

[Bill Wilson]

The wireless systems I use for video production, use rechargable Lion's not alkaline based. That said fully charged 8.2-8.4 volts; minimum operating voltage 7 volts. They are rated 600mah's & run the receiver that draws 76 ma. for a good 8 1/2 hours.

[mediatechnology]

Thanks Bill. So about 7V on that system.

I did discharge testing on Alkaline AA's for two different products using the ISD Chipcorders years ago and I found that on them - with those two relatively low current products - that the EOL was around 1.25 volts per cell.
One of them was an intermittent duty verbal circuit identifier and I had to log it for months to see how long it would go. That one felt like the Energizer bunny.
The other one I was able to plot a discharge curve on since it ran down in 4-5 days.
The output impedance at that point began to rise significantly right before they fell of the cliff.
My wife's pager works down to about 1 V before it alarms.

7 - 7.3 volts we see works out to be about 1.2 V/cell in an alkaline 9V.

The reason why I'm asking is to determine how much battery headroom exists running ICs designed for 30V operation on either 9 or 18V.
Unfortunately a THAT1510/1512 needs 18V with its 10V minimum but a 124X or 1646 can run below 8V. There's not much headroom though.

[mediatechnology]

Thread from the past.

I'll add to the dataset that 7.6V is the end-of-life voltage for a Zircon water leak detector.
It reached end of life around 12:30 AM this morning and began beeping.
I have about eight in the house - two in the kitchen. This one was behind a snap-on kick panel underneath the sink.
What a fun way to wake up.

Why is it that smoke detectors always reach end of life during the night hours?

Will confirm that most of my weather instruments signal end of life for AA and AAA batteries around 1.35V/cell.

[JR.]

Thread from the past.

I'll add to the dataset that 7.6V is the end-of-life voltage for a Zircon water leak detector.
It reached end of life around 12:30 AM this morning and began beeping.
I have about eight in the house - two in the kitchen. This one was behind a snap-on kick panel underneath the sink.
What a fun way to wake up.

Why is it that smoke detectors always reach end of life during the night hours?

perhaps because of cooler indoor temperature late at night, early morning.

JR

Will confirm that most of my weather instruments signal end of life for AA and AAA batteries around 1.35V/cell.