Those are battery holders with integrated wire connectors for AA and AAA batteries. It is partly a derivative of http://www.thingiverse.com/thing:9805 .
The electricity from a battery is conducted to wires through M3 countersunk screws and M3 embedded nuts. Wires are fixed between holder connectors and embedded nuts. A battery holder can be mounted using two M3 countersunk screws.
There are several holder models published both for AA and AAA batteries. Their filenames start with a battery type followed by an amount of batteries in a holder.
- Print it (AA_1_Battery_Holder.stl for a single AA battery, AAA_1_Battery_Holder.stl for a single AAA battery). If you are printing from ABS plastic and have a cooling fan (e.g. http://www.thingiverse.com/thing:32465 ) make sure that the fan is turned off. I have printed it using ABS plastic with 0.3mm layer height.
- Clean the wire holes (which lead from bottom to nut holes) with a 2mm drill bit. You may use the following technique for cleaning holes: http://vimeo.com/14492980 (starting from 00:58 of the video).
- Prepare 2 M3 nuts, 2 M3 countersunk screws, and 2 wires (per battery, see Details.jpg).
- Put the M3 countersunk screws into battery connector holes (from battery side).
- Insert stripped wires into 2mm connector holes and make sure that wires are visible in nut hole. It is shown on ConnectingWires.jpg.
- Embed nuts and gently tighten screws to make a reliable connection, but do not over tighten them because the plastic part of a battery holder may crack.
- Use another two M3 countersunk screws (not shown on Details.jpg) to attach the battery holder to a thing which needs it. For example, I have used it for boosting several toys which mistakenly believed that 1.5V alkalines are better to use than 1.2V NiMHs (UseCase.jpg). :-)