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
Batteries are modular. If you wire them in series, their voltage “stacks”. If you wire them in parallel, their capacity stacks. Because alkaline batteries produce around 1.5V per cell, you can design your device to work with any multiple of 1.5V, then just wire up alkaline batteries (of any size) in series and get the voltage you need.
However, as you’ve noticed, not many devices rely on only 1.5V. Most work with 3.0V or more. Alkaline battery chemistry only produces 1.5V per “cell” though, and a single alkaline battery typically only contains a single cell. Packaging more than one cell together increases cost, so it’s cheaper to simply require two separate batteries.
There is one type of alkaline battery that combines more than one cell though; the 9V battery. Many 9V batteries are actually six AAAA — yes, four-A, which isn’t a size you see often — batteries packaged up as a brick. More modern 9V batteries use something called pancake cells stacked up like sandwiches though. They made the switch because you can get more capacity in a single 9V battery this way, because it uses up more of the space. Since consumers prefer batteries with more capacity, this pushed the industry to move away from the 6 AAAA battery packaging.
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