Battery Crates for Blister Packs

I’ve been printing these Beer Crate Battery Storage boxes for a while to deal with my battery hoarding issues, and for the last few months there has been a pack of LR626 cells that I knew would not fit any of the designed crates (the cells are way too small). It annoyed me enough that I modified one of the designs to hold them in their blister packs.

The Original Crates

The starting point was Beer Crate Battery Storage by YK42, a set of little stackable beer crates, each one labelled and with holes sized for a particular battery. There’s a crate for pretty much everything: AA, AAA, C, D, 9V, 18650s, 21700s and a whole run of coin and button cells from CR2477 down to LR41. They print in PLA without supports or a raft. Here’s some of my hoard, already sorted into them.

Stacks of 3D printed beer crates in black, white, grey and red on a wooden shelf, each labelled with a battery size (2016, AAA, 18650, 2025, 2032, D, 9V, C, LR44 and A23) and filled with that type of battery — Most of the batteries in the house, sorted by size

YK42’s version is a remix of the original beer crate by Marzochi, with the stacking features from TontoTraveler, plus labels and a lot more battery sizes. Handily, there are also empty crates in three heights, 35mm, 43mm and 51mm, to build your own from¹.

The Problem with Tiny Batteries

The batteries I wanted to store are AG4/LR626 button cells, which come on a sheet that’s easy to cut into sections, so there are two to a card.

A green PoundMax blister card holding two small silver AG4/LR626 button cells, lying on a wooden desk — Two LR626 cells, cut from the sheet

The crates that take loose batteries were no good for these. The smallest crate in the set is for LR41s, at 7.9mm across, and an LR626 is smaller still at 6.8mm across and 2.6mm thick.

Measuring Up

Yeah right, I eyeballed it. As you will see later, measuring would have been helpful, but I got close on the first attempt.

The Design

The plan was to take the 35mm empty crate (about 68 x 54 x 40mm) into FreeCAD and add a row of ribs across the inside, making slots for the cards to stand up in.

Nothing fancy here. The empty crate went in as a mesh, then I sketched a single rib, padded it out and used a linear pattern to repeat it across the crate. Finally I cut a cylinder out of the middle of the ribs, to match the existing crates.

A FreeCAD screenshot of the crate model, with the model tree showing the imported empty crate mesh and a body made of a padded sketch, a linear pattern and a cylinder cut, and the 3D view showing the crate with a row of ribs inside and a curved dip cut across their middle — The whole model: the empty crate, one rib, a linear pattern and a cylinder cut

One thing the new crate doesn’t have is a label on the side like the originals, because text is currently a bit of a pain in FreeCAD².

The First Attempt - Mind the Gap

The first print looked alright from a distance, but up close the ribs didn’t quite reach the side of the crate, leaving a little gap at the end of each one. I had lined them up by eye in the normal view, when I should have switched to wireframe mode to see where the ribs actually met the wall.

A black 3D printed crate seen from above, with a row of thin ribs running across the inside and a hand-drawn white arrow pointing at the end of the ribs, where they stop short of the crate wall — Mind the gap: the ribs stop just short of the wall

The first attempt in 3D, gaps and all. You might be able to see the gap in the wireframe view, the one I should have checked

It wasn’t the only problem either³. The ribs were a bit too close together and a bit too thin. The cards did fit, but only because the ribs flexed out of the way to let them in.

A quick round back through FreeCAD to thicken the ribs and make sure they intersect the walls of the crate, and we were sorted.

The Finished Crates

The final prints came out nice, though a bit of stringing means my filament was probably a bit damp, despite my new filament storage.

Looking down into a black 3D printed crate with four green blister cards of button cells standing upright in its slots, with a few fine wisps of stringing on the crate and other filled battery crates behind it — Four cards, all standing up on their own, stringing and all

download .3mf

The finished crate in 3D

The 3MF file is available here if you want to print your own⁴.

Final Thoughts

If you’re using the crates already you might as well try this one. I’ll think about adding the text to them once the new version of FreeCAD is out, but chances are, as this works as is for me right now, I will never get to it.

The crates are licensed CC BY-NC-SA, so any remix, including this one, has to be shared under the same licence. ↩︎
I’m looking forward to the 1.2/26.3 release, which has much better text support, so labels may turn up in a later version. ↩︎
Annoyingly, it’s hard to see in the 3D view that the ribs don’t connect to the wall, so the photo above shows it much better. ↩︎
I’d be surprised if you can spot the differences from the model you saw earlier. ↩︎