When you are replacing batteries make sure you are stacking them correctly. There is a + marking inside the AvBat both replacement batteries + side should be towards the + on the AvBat.

How to Change the Batteries

How to Remove the Original Foam

Installing new Foam

Changing the foam in the case with the metal band is the same as the fully plastic one. There is a piece of metal under the foam in the case with the metal band, that should be removed to ensure the new foam adheres properly.