This is a customizable storage box for cylindrical batteries. It has presets for:

• AAAA
• AAA
• AA
• A
• 18650
• C
• D

The included .stl file is for 6 x 2 D-cell batteries which is the largest the Ender 3 can print (well, maybe if you turn it at an angle you might get more).

The tolerance is a buffer around each battery in both X and Y because there is a slight variation in the size of the batteries. I measured several ones (if I had different types of batteries) and chose the largest as the default.

The uploaded .stl was created with the following parameters:
battery_type = 33.3; //[8.3:AAAA, 10.5:AAA, 14.5:AA, 17:A, 18:18650, 25.33:C, 33.3:D]
battery_height = 60.7;
height_percentage = 50;
number_of_rows = 6 ;
number_of_columns = 2;
inner_wall_thickness = 1;
outer_wall_thickness = 2;
bottom_thickness = 2;

// Distance around battery. Increase if too tight. Decrease if too loose.
tolerance = 0.5;