We learn about different battery sizes when we're kids, which is when I learned it took six D batteries to play cassettes on my boombox for about four hours- and that D batteries were heavy and cost a bundle.
But we're always left with one unanswered question- what happened to the "B" batteries?
To find out we have to go back to the 1920s, when battery cell sizes were standardized by the government agencies, War Industries Board and American battery manufacturers working to create a uniform product:
In 1924, industry and government representatives met again to figure out a naming system for all those cells and batteries they had just standardized. They decided to base it around the alphabet, dubbing the smallest cells and single-cell batteries “A” and went from there to B, C and D. There was also a "No. 6" battery that was larger than the others and pretty commonly used, so it was grandfathered in without a name change.
As battery technology changed and improved and new sizes of batteries were made, they were added to the naming system. When smaller batteries came along, they were designated AA and AAA. These newer batteries were the right size for the growing consumer electronics industry, so they caught on. C and D batteries also found a niche in medium- and high-drain applications. The mid-size A and B batteries simply didn’t have a market and more or less disappeared in the U.S..
While you typically won’t see either A or B batteries on American store shelves, they’re still out there in the wild. A batteries were used in early-model laptop battery packs and some hobby battery packs. B batteries are still sometimes used in Europe for lanterns and bicycle lamps. According to Energizer, though, their popularity is dwindling there, too, and they might be completely discontinued.
-Via mental_floss
The famed Global Village is a junkyard of nonstandard anything.
I hope C batteries go away soon. Half the capacity of D cells, yet the same price. Just use 2xAAs instead of 1 C. AAAs are similarly less than half the capacity of AAs while being no cheaper, and sadly used where AAs would work fine. I do try very hard to avoid almost anything that takes Cs or AAAs (flashlights, radios, etc).
I'd like to see 9V go away, too. Expensive for the very little power they provide, and no longer needed now that very cheap and efficient voltage booster circuits are available. A couple AAs will fit in the same space and do the job, no problem.
D batteries were the size of the original EverReady flashlight batteries. They were "LeLanche" cells, which were improved to form "Heavy Duty" batteries, hence the confusing title, which makes no sense today. On the plus side they don't leak, unlike alkaline batteries.
E batteries exist, too. Longer than Ds, they typical put 4xE batteries inside an (alkaline-) lantern battery pack. Although it's not unusual to see numerous AA cells in there, instead, if they happen to be cheaper/more available at the time.
Why just alkaline? Because "Heavy Duty" batteries are more amenable to different shapes, so they have soft (paper wrapped), square cells inside of those.
The difference between cylindrical and rectangular cells gives "Heavy Duty" batteries a real advantage in 6V Lantern, and 9V batteries. They're only about 25% lower capacity than their alkaline counterparts, while being dramatically less expressive (50c for 9v at dollar stores and $2 for 6V lantern batteries at Harbor Freight and others).
When you need to replace the 9V batteries in your smoke alarm, you're best served taking a trip to Dollar Tree, alkaline batteries are wasted on such a low-drain task. Low-self-discharge NiMH rechargeable will be cheaper in the long-run, but it'll take over a decade to pay them off. Smoke alarms might not use 9V batteries by then. Some states already require them to have permanent 10yr batteries included (smoke alarms are supposed to be replaced every 10yrs, anyhow).
AAAA batteries are a thing, too. They're the size of the 6 cells squeezed into alkaline 9V batteries, and that's the cheapest way to get them if you've got an old hearing-aide, pen-light, camera, or other device that still needs them.
I don't expect cell phone manufactures to standardize any time soon. That would mean lower capacities or wasted space. I'd be happy if they'd agree on pin-outs. I can take the battery from one Samsung phone and stick it into another, because they're pin-compatible and the connector is in roughly the same place. You might need to shim around it, and may be too big to put the back cover on, but it offers a level of compatibility in emergencies, for maintenance, etc. Sadly, the battle right now is whether batteries are user-removable at all, which is a further step removed, still.