Travel AA and AAA battery holder

When we travel we have a various number of AA and AAA batteries for various things.. they tend to get out of hand and mixed up in various bags. I figured I could design a simple friction fit case that could hold 2, 4, 3 batteries either in a linear or 2x2 array. The case has a top and a bottom and we use a simple heuristic: If the dimple is facing up the battery is charged.