This is a remix of @BlackBird7171's Expandable Battery Dispenser (https://www.thingiverse.com/thing:399744/#comments), scaled according to @mc2lagrange's suggestion in the comments. Fits AAA batteries perfectly.

Print with fan to avoid sloppy corners, but no support should be necessary. In the picture, the left one is accidentally done without fan, the right one with a proper fan duct.

The extension has been repaired by running it through netfabb and now prints correctly.