ELI5. Why do most devices requiring AA or AAA batteries need at least two. Why not create a standard battery that is the equivalent of two or have common circuitry that only relies on one battery of a similar low profile?
In: Engineering
Because then you will have just added an additional type of battery making things more complicated, but also lost some of the efficiency of scale that allows AA and AAA batteries to be so cheap by splitting their market into at least 2 (if not more if you have to account for the different space configurations and alignment that 2 batteries can take up)
The batteries only produce 1.5V so putting two in series makes it 3V. There isn’t anything stopping the creation of a 3V battery and you can often find specialty ones. But with the same chemistry and size, it won’t last as long as
Creating new standards is hard and probably not worth it. Some devices need 1 battery, some need 2 or 3 or 4. So having separate special formats is unlikely to make sense.
As a side note, most(all?) 9 volt batteries are just 6 AAAA batteries in a trenchcoat.
Most devices need something like 1.8-3.3V to power microcontrollers and LEDs. One AA/AAA battery does 1.5V, inherent from their chemistry. There are devices that work fine off 1.5V, either by having a small internal voltage doubler circuit or just by having ultra low voltage components.
There *is* a 3V AA-like format using lithium like coin cells do. It’s called CR14505 and it’s like 5$ a pop. It has similar energy capacity to the much cheaper 1.5V batteries.
There have been many attempts to replace two AA or AAA batteries with one battery package but they never gain traction against the established standard. AA and AAA are not compatible though so you can’t replace both with a single standard.
Form factor most likely, decades of products made to fit individual cylinders producing 1.5 volts would mean your new shape would possibly not fit them, plus many devices now using lithium ion batteries.
There is also the wiring not being the same, if they are in parallel then it is only using 1.5 volts but if they are in series then it’s a multiple of that.
Technically, though only really worth it in an emergency, since AA and AAA (and C & D) produce the same output, you only need AAA batteries and can pad the caps with foil so they work in the device. The lifespan of those batteries will be less but sometimes it’s all you need.
The voltage of a battery is based on its chemistry. The power comes from a chemical reaction and each reaction has a certain voltage. Adding more material increases the current it can produce, and the overall power, but not the voltage. The only way to increase the voltage is to have multiple cells in a sequence, i.e. two 1.5v batteries wires from end to end are 3v (which is why they are often installed in opposite directions)
1.5v is what regular non rechargeable batteries use. Nickel metal hydride is 1.2v which allows substitution with alkaline batteries but sometimes stuff doesn’t work as well on the lower voltage. Lithium ion is around 4v.
So if you wanted to have a 3v battery standard, you’d need to either find a chemical reaction that produces 3v or you’d need to just stack two smaller 1.5v batteries in the same casing. Which adds cost and complexity to the manufacturing and doesn’t really buy you anything – if the device was big enough for multiple cells to fit, you would just use multiple cells to get the desired voltage. And there’s enough stuff out there that works with one alkaline battery or two or three that making a standard that’s, say, 3v, means you would still need to have 1.5v batteries on hand for devices that only need one cell or that need three cells (4.5v)
IMHO a much more valid complaint is devices that use AAA batteries despite having room for much larger batteries. AAs have a lot more capacity and I have a couple things around my house that are heckin chonkers that use AAA and need to be replaced far more often. The worst offender is my smart scale which is 12″ x 12″, but I also have some really big mini split remotes with screens. Low key annoyed every time I have something that clearly could have fit AAs or even larger in it and they designed it to run off AAAs
Your standard 9v battery is 6 little batteries inside it. Maybe AAAA sized? So yeah it totally could be done if it had been done early enough in battery history. Too late now tho for the reasons others have mentioned.
There are, for example vapes and flashlights using 18650 and other cylinder cells at 3.7
But much like the micro USB, the cheapo electronics import industry hasn’t caught up and it’s much cheaper to buy a AA housing vs a cylinder one
Plus your average dad’s never heard of em
Because with two batteries you can have different configurations, even if the arrangement looks the same. If you wire two 1.5v, 300mAh batteries in series, you get a single 3v, 300mAh power source. If you wire them in parallel, you get a single 1.5v, 600mAh power source.
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