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by birdman3131 637 days ago
Because what is in a 9 volt is 6 AAAA batteries. They are smaller than even an AAA battery. Only thing I know that uses them is some of the surface drawing pens and the like.

That said if you need 9 volts ask a church. I know we would gladly hand you a box of half full ones as you have to pull them out of the wireless mics before they die. And older Shure mics are 9 volt.
2 comments
computator 637 days ago
> Because what is in a 9 volt is 6 AAAA

But then the question would shift to: Why wouldn’t a AAAA cell have the same energy density of a AA cell? Remember that the argument is about energy density, not total energy.

By the way, I think that fsh’s reply is a convincing answer: it’s the extra packaging that kills the density.

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DanTheManPR 637 days ago
The current collector also takes up relatively more volume, on top of the packaging (the wall thickness would be the same, and it's not a trivial part of the volume of small cell batteries).
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ssl-3 636 days ago
Perhaps interestingly, some 9V batteries (Varta comes to mind) have a stack of cells with rectangular cross section instead that of a cylinder (like AAAA), which suggests an improvement in energy density.
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