This customizable and extendable model allows you to define the container (shell) size and battery size and it will generate a model to your specifications.  I expanded on the original file to make it easier to add new and custom battery sizes and to make the code easier to read for those new to OpenSCAD.  I also added some error correction code that will prevent issues where the battery is too big for the shell.  I used a sharpie marker to color the names, but I'm sure there are other ways to add contrast there without multi-filament.   I have included the files of the models I printed here, but it is flexible to create whatever sizes you need.