Why do so many products use serial arrays of 1.5volt batteries instead?
It seems kind of weird, I mean the 9v is smaller a D cell, and of about the same overall volume as a C cell. It is easier to stack up and pack into a tight container, so why are they not used more?
I also heard that 9volts are really just 2 AAAA’s shoved together. Can anybody confirm or deny this? I don’t have the guts to rip a 9v apart myself to find out. . . . (and how the hell are 2 AAAA’s getting to 9v?)
Actually, if you rip open a 9v (it’s not difficult), you’ll find 6 small cells. Each one is a volt and a half, so they add up to 9. It actually makes 9v’s the only type that actually qualifies as a ‘battery’ (in the sense of ‘a collection of cells’).
The fact that these are really small cells is the reason that 9v’s aren’t used more often. They can’t get the current needed by a lot of devices. Only those that don’t draw much power can use one.
9V batteries have a lower current capacity than 1.5V batteries (like AA). Thus, they are good for use in devices that have high voltage requirements, but very low current consumption. Such as old “transistor radios”, which had discrete transistor components instead of integrated circuits. Now, with the prevalence of IC’s, which can operate on a much lower voltage, it makes more sense to use a couple AA’s, which will last longer than a 9V.
There are still some applications for the 9V battery. A good example is my LED bathroom scale. As the scale is used for mere seconds a month, it uses very little current. But due to it having LEDs, it requires a higher voltage. So a 9V battery works perfectly, and is easier to change than 4 or 6 AA’s.
I actually had to buy a 9V battery a couple months ago at a gas station, and the young girl behind the counter gave me a strange look and asked “what the heck are you going to use that for?” Yeah, I guess they’re really not used that often anymore.
9 volt batteries are only really useful in situations where you have low current draw, but need a relatively high voltage in a small space. Smoke detectors and battery backups of digital answeing machines and alarm clocks are prime examples; you need at least 5V to drive the electronics, but the devices draw nearly nil current if there’s no smoke, or if the clock is plugged in.
Other electronics draw a lot more current, but don’t require a very high voltage (3V in the case of my Handspring Visor). A 9V battery would easily drive the device, but would run out before you could say “alkaline”. So, it makes more sense to use a cheaper and smaller pair of AAA cells.
I think it is the current draw, yes.
But I’m not sure about the lower voltage/current draw of newer devices with IC’s. With all the bells and whistles, they seem to go through batteries pretty quick. I have an older transistorized radio that uses 9 “D” cells, which sounds like a lot, but the current draw is less than 50mah, so the batteries last years.
also lantern 6v batteries which are actually made of 4 “b” cells, not to mention many rechargable batts like car, emergency lights, ect…
Back to the OP
I use lots of 9v in telephone testing equipment. I would much rather use all AA’s due to the volume I go through and the price.
I have a guitar tuner that takes a 9V. It has a meter in it. How much current does the meter movement draw? It has a couple LED’s, too and a little light to illuminate the meter face. Sort of an old one - these days a lot of them have LCD displays rather than an actual meter.
Cool thank you for all the replies. 
I was wondering what ever happened to B cells. . . or just A cells for that matter!
Kind of werid though, I can remember 10 years ago having a ton of devices that used 9v, yesterday I was unable to find a single one!
Needed plugs for it, heh. The resulting epoxy combinationt had I had to use instead isn’t pretty.
(hehe, defintly not going to be able to change those batteries. )
Cecil Adams on How come you never see any B batteries?
Why did some models catch on while others did not? Was it the form factors, or was it that there was not a big enough difference between, say, A and C batteries for companies to differanciate. Obviously it is cheaper to maintain everything if a company only has to maintain the equipment needed for a smaller number of possible combination of parts, but what was the deciding factor between the different form factors?
Here’s a picture (doctored) illustrating the size of the “b” cell in the sense we’re talking about: http://exn.ca/Stories/1998/06/16/51.asp
If you’ll notice, that article ends with “Next week: B-batteries and old time radios”. If you dig into this subject, you find that, confusingly, early radio equiptment referred to “A battery” and “B battery” to designate batteries used for specific purposes - IIRC, they had separate batteries to supply the filament current for the tubes, and the actual plate voltage.
And here’s a blurb on the “A”, “B” and “C” batteries in old radios:
http://www.bartbeck.com/page21.html
The “B” battery was plate voltage, 45, 90 or 135 volts. Apparently there was also a third “C” battery to supply grid current.
That’s correct, the B+ designation for certain circuits voltage is still called that because of the old "A’ and “B” batteries.
Very early radios required a “C” section battery as well. I have a couple tube ‘portables’ (among the first ‘boom boxes’ I guess) that require separate batteries, 9 volt, high current “A” voltage for the filaments of the tubes, and 90 volt low current “B” voltage for the plate volatage. While 10 9 volt batteries in series would suffice, I opted for 60 “AA” batteries in series because of the increased operating life compared with 9 volt batteries. (About 400 hours or so with modern alkalines)