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
Electrical engineer here, there are many reasons for this:
1. While many devices need 3.3v (usual voltage from two 3.3v cells), many more need 5v, 12v, 9v, or some other voltage; rather than having to make a large number of batteries in different voltages, it’s easier to simply standardize the batteries and use more or less of them
2. Some devices need a positive, negative, and neutral voltage to work properly. Having two or four alkaline cells with a tap in the middle is an easy way to accomplish this
3. Multiple smaller cells gives you a bit more flexibility in allocating space and weight for power storage — having a giant brick that can’t be broken up into smaller bits is gonna make life a lot harder during board design.
4. The options for raising the voltage coming out of a battery are to combine a bunch of small cells (more expensive and reduces power capacity), add a switching DC-to-DC converter (more expensive, can add some nasty ripple voltages if you don’t cram in even more electronics, those extra electronics also reduce capacity, and disposing of the battery becomes much harder), use a chemistry that naturally ouputs a higher voltage (even more expensive, and you’re not gonna get that much more out of it), or use something that isn’t actually a battery such as a fuel cell or radioisotope generator (ridiculously, heart-stoppingly expensive, dangerous, hard to source, possibly illegal, and damn-near impossible to get safety certifications for). It makes more sense just to get multiple cells and do any voltage conversion onboard the device.
5. If a single cell turns out to be faulty, it’s cheap to replace; if a cell in a battery fails, it costs more to replace and it’s harder to diagnose
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