For many people integrating batteries into their projects, this is true and you can simply take most off-the-shelf cells with the right voltage profile and put

For many people integrating batteries into their projects, this is true and you can simply take most off-the-shelf cells with the right voltage profile and put them into some series/parallel config. At least with lithium-ion technologies, for larger applications, this ignores a lot of the degradation phenomena and electrochemistry of the battery.