Question

Different devices require different type of cells. ​

Answer 1

Answer:

First off, battery sizes are standardized. So companies work with the standards.

Secondly, I don't know what you mean by “most things take two batteries”. Not in my neck of the woods. I see things using 2, 3, 4, and 6 batteries. Radios, remotes and flashlights make the bulk of it. Two's, three's and four's are common. The odd ducks are devices that use one or eight batteries.

Consumer items generally use the standard alkaline sizes but specialty very high power devices like robotics high power flashlights and such use the new standards in lithium rechargables like the 18650. Those are single cell high output. They haven't gone mainstream yet perhaps due to fire fears from the Samsung debacle and skittish consumers.

Those two extreme cover very low power and very high power devices. Everything else is in the middle