Print your own AA battery packs!
Want to power your projects but don’t want to buy dual AA battery packs for $2.29 apiece? Well then we’ve got something in common.
At Iridescent’s NYC studio, we make our own using our MakerBot Thing-O-Matic, and if you’ve got access to a 3D printer you can make your own durable and functional battery packs! You’ll save the trip to the store…plus, our battery packs end up costing ~25¢ in materials each, so you’ll save some money, too.[picky person footnote]
1) Gather your materials
You’ll need a few simple parts which you should be able to pick up at a local hardware store, if you don’t already have them lying around:
- 2 machine screws
- thin uncoated metal wire (about 24 gauge is what we use, but a little thicker is ok too, so long as you can bend it)
- screwdriver for the screws
- pliers for the wire
The finished product should end up looking something like this: (though it may not be quite as vibrantly coral red as ours!)
We use 8-32 machine screws; the ones pictured here are 1/2″ in length (McMaster-Carr part number 90272A194 if you want to get them online). The wire at the other end is 24 gauge steel wire, though an uncoated paper clip would work, too.
2) Print the battery pack file
Here’s a screenshot from OpenSCAD of the file we print from:
The source files, both .stl and .scad, can be found over at The Thingiverse. This is Thing 145714.
We print these in PLA, on a raft, using a 15% infill, on our (now vintage) Thing-O-Matic. You may want to try a few different settings until the print comes out to your satisfaction on your own particular hardware/software. Please also note that the OpenSCAD file is provided so you can tweak any settings you might want to. (The script includes support for printing different battery sizes as well as different numbers of batteries per pack. Thanks to the previous coder, Juan Gonzalez-Gomez, and original author, Nikolaus Gradwohl, for open-sourcing the code on which our iteration is built.)
3) Add the electrical contacts
To make your battery pack into a 3V source, you’ll connect the batteries in series like shown at the top of the page: screw terminals on one side, and a wire connecting the other battery sides.
Start by screwing your screws in. (They may need a little convincing.)
Sometimes you’ll have a spare bit of plastic from the print in the way of the end of the screw. If that happens, back out the screw until it’s not in the way, and cut off the extra plastic:
Wrap the wire around the end opposite the screws. What matters most is that the wire will touch both of the battery terminals, so don’t worry about it looking pretty, just worry about it touching the batteries.
We flatten the wires out with the flat part of a pair of pliers, so the wires will lie more flat on the ends of the packs:
Look from the side to confirm that there aren’t any gaps between the contacts and the ends of the battery—tighten the screws a bit if you see a gap so it’s gapless like this:
4) Pop in your batteries, tighten them in place, and test it out
Put your batteries in head to tail, tighten them in place (don’t overtighten, you’ll dent the thin cap on the battery), and test the battery pack out by attaching it to a small motor, LED, or something else that will run on 3V. Or just test it using a battery tester or multimeter.
With practice you can assemble one of these in around a minute. So get practicing!
4a) Troubleshooting/redesign
If you finished assembling the pack but it’s not working, here are some parts to check:
- Are the batteries charged?
- Are the batteries oriented the right way? They should be head to tail, not head to head
- Are the screws and the wires touching the batteries? Look from the side and make sure there are no gaps—even a tiny gap will open the circuit and stop the flow of electricity. Try tightening the screws a bit if the batteries are loose.
- If you’re testing with an LED, is it facing the right way? Remember, LEDs are diodes, so they’ll only light up when their longer leg is positive and the shorter is negative. Try flipping the LED the other way around.
5) Do something neat!
What will you power with your battery pack? Maybe a motor, an LED, an Arduino project, a door-opener, an octopus arm, a homework-solver, a microscope light, a tiny helicopter, a speaker, a mechanical theater…
Send [email protected] some pictures of what you made and we’ll put them up here!
Footnote: Ok, I didn’t figure in the cost of buying and maintaining your 3D printer. To be fair, the ~25¢ figure is the approximate marginal cost of the plastic of the printed part and the hardware needed to assemble one of these battery packs. So for the econ students out there: I’m considering the printer, computer, etc., as sunk costs. Now that that’s settled, go make a battery pack!