There are odd cells out there but for the most common ones they all seem to be around 1.2 to 1.5 volts. Lead-acid puts out 2 volts and lithium cells are 3.7volts. Is this just due to the valances of the various elements in the reactions?
It’s an intrisic property of their chemistry, just like melting point or density.
Another one is the 0.7 volt drop in silicon semiconductors.
Historically, carbon-zinc-acid batteries were the standard for flashlights and stuff. They are 1.5V. As noted that was just the way the chemistry came out. Since so many devices were based on these replacements needed to be around that voltage. E.g., alkaline batteries are a little over 1.4V. Rechargeable NiCd batteries are 1.2V which makes them unsuitable for some devices.
Some batteries are actually, well, batteries- having several cells in them. E.g., 9 volt alkaline batteries have 6 small button cells inside. Some types are a “stacked” sequence of layers of cells. This results in a times 6 (for example) multiplication of the base voltage so the range can be from 7+ to 9.6 volts.
Depending on how new the cell is and manufacturing variations, even a 1.5V cell can vary a lot. So devices used to be able to handle the variation. But with newer digital devices not so much. E.g., a digital camera might not turn on with batteries that are still at 1.3V.
No way! Well, now I need to cut one open. How much damage to my person can I expect?
Just don’t cut yourself on the metal case.
I just love home science experiments.
Great article, thanks. 
Do any of the other 9 volt brands use button batts like ftg said?
Some 9v used a stack of rectangular cells. I haven’t cut one open in years, so I’m not sure if any are still made that way.
I would think the volumetric efficiency of a stack would be higher than using six cylindrical cells. If so, you would think all manufacturers would use a stack, since it gives an advantage over competitors in terms of lower source resistance and/or longer life.
If I’m bored today I’ll cut one open.
If you cut open a lithium cell, you won’t be bored for a few hours. Depending on wait times at emergency medical centers near you, that is.
(For the uninitiated: this is supposed to be funny. Lithium cells are pretty dangerous to cut into as the lithium part is likely to burst into flames.)
I’ve only ever seen the 6x AAAA configuration
None, but last time I unwrapped a 9V battery I got six AAAA cells, not button cells.
I did it as an 8 year old for curiosity and again later in High School for an electronics class. Not much danger at all.
The old Lantern Battery (6v) are also made up of cells. Typically 4 to get to 6v. The cells are a bit bigger than a ‘D’ cell, I think they were classed as ‘F’ cells.
Correct. Way back when you could buy F cells, but they faded out long ago. For a long time about the only place you could find F cells was inside lantern batteries. These days, many lantern batteries contain four D cells with spacers to make up for the difference in height between D and F cells.
Here is an image showing an F cell vs. a D cell. The F cell pictured is what you typically used to find inside lantern batteries.
I personally have never seen button cells. I have seen stacks of rectangular batteries like @beowulff mentioned and I have seen six AAAA cells though. The ones I have personally seen looked like the left stack in this image, and the I have also seen the cylindrical cells like the bottom image.
All the higher voltage batteries have multiple cells. Those big square 6 volt lantern batteries have 4 big cells, probably C or D. Same with cordless tool batteries of any voltage. You can rebuild your Dewalt 18v battery pack by taking it apart and inserting new cells that are available. You do need to spot weld the connections. We used X cells in the microgravity experiments at NASA. They are lead acid and larger then a D cell and have 2 volts per cell. They could survive vacuum, low G and high deceleration quite well.
I wonder about the old 90 volt radio batteries. They make kits today to build one out of 10 9-volt batteries but I wonder if that was the way the originals were constructed.
Usually D or F, as mentioned upthread. It wouldn’t surprise me if some el-cheapo ones had C batteries plus spacers but I’ve never seen one like that.
I always assumed that they were built more like the way car batteries are built today, i.e. banks of plates like so:
An older lead-acid battery:
I’ve never taken an old radio battery apart though, so this is just a guess. It’s been decades since I’ve even seen one.
That reminds me that I have a 1970s Sanyo NL-5100 aviator’s flashlight (the rectangular ones with clear and red lenses). I thought about replacing the cells, but last time I looked at it (maybe 15 years ago) I didn’t see how to open it.
Honestly, any old flashlight or lantern like that isn’t worth putting fresh batteries into. LED is such a superior technology to the old incandescent.
One of my many jobs on the ship, was going around and testing and changing out as needed the pair of 6 volt batteries for the emergency lighting.
I was thinking how long would the equivalent lumen LED bulb last on a pair of 6 volt batteries? I’m pretty sure they were good for up to 4 hours back in the 80s. I’m seeing something that says in 2016 the lights were lasting 30 hours and were smaller, but I’m not finding any details.
Looks like the 30 hours is correct and that they’re mostly using rechargeable battery now:
If you ever do find a trove of old radio (higher voltage) batteries, some used quite a bit of silver content so check before trashing.