Stackable, snapable 18650 battery case. Super easy DIY variable-voltage 18650 battery packs without pesky cell soldering, and allowing for simple cell replacement. (useful if using reclaimed 18650 cells from...say...laptop battery packs)
Now includes 2, 5, and 6 cell versions. Haven't tried printing those, but should work just as well.
tinkercad link: https://www.tinkercad.com/things/4mitzZL41nM-18650x4-snap-case-12ga-wire-v81
v8.1 (see the pix of the grey case)
increased hole size to accommodate 12ga wire
moved wire holes up by 2mm so wire would contact battery ends closer to on-center
put cut-outs beneath batteries to make it easier to pop the buggers out
added negative wire blocks...made out of a cut medicine bottle. :-) (for a 3d printed one, see the remix)
see the most-excellent remix @ http://www.thingiverse.com/thing:2280467 for a top-snapable lid!
I wanted to build a high-voltage battery pack from laptop-reclaimed 18650 cells. DIY solutions either required:
soldering to the cells (heat can be bad for the cells, no good way to swap out bad cells)
spot welding (spot welders for this application are $$, also no way to swap out cells that go bad)
building (somewhat) elaborate enclosures that allowed for battery replacement. (I didn't have all the machining tools necessary)
All these solutions also required sanding/grinding off all the nasty little bits of nickel strip that remained after separating the batteries from their laptop bodies.
Inspired by and building on enif's excellent 18650 battery case with built-in-spring ( http://www.thingiverse.com/thing:456900 ) , I did some tweaking. My solution allows for individual cell replacement while avoiding both heating the cell and the need to grind off the little residual bumpies! As a bonus, it’s extendable (adding/reducing voltage is trivial) and reasonably cheap. (assuming you can source a 3d printer)
Given the number of hours I spent revising, I wouldn’t say it qualified as a non-elaborate solution. For you however ... some 12ga stranded wire, 8mm m3 grub screws and (optionally) 10mm pan head m3 screws and you too can have a tower of power.
Model is for a 4 cell stack. However, it’d be easy enough to slice up the STL and splice in more cell slots in Tinkercad (which is what I used to begin with)
I printed mine @ 0.3mm resolution using PLA. Depending on your printer’s calibration (and mine...) you may need to scale the STL up or down 1-2%
The interconnect wire is 12ga stranded. It’s insulation is sliced (carefully) to expose 1/2 of the wire, for the length of the battery case. (picture is worth 1000 words) Battery modules have holes @ each end for the 12ga wire. Stranded gives the best connection if you’re lazy as I am and don’t bother to smooth the battery ends.
m3 grub screws hold the batteries tight and squish the wire against the battery terminals.
The current model’s wire holes are too small for 12ga wire. I drilled them out to fit.
Battery modules stack front-to-back to allow wire to loop from the + end of one set to the - of another. If they don’t snap together firmly enough for you, there are aligned holes for m3 pan-head screws to snug things together. This isn’t the optimum power-to-volume ratio, but it’ll work well enough for me to have the stack secreted away in paniers or in a bag mounted to a rear rack.
I haven’t actually used them in their intended application, as I realized that:
I wanted 10ah minimum of range
My recycled laptop cells averaged around 2000mah
My recycled laptop cells generally aren’t rated for the load an ebike will put on them.
I was out of season to ride the ebike, as fall had set in and I was driving kiddos to school every morning.
As a solution I’m thinking to build another stack to attach in parallel to the first. This should both double my range, and halve the amp draw on each set.
Jig to make cutting the insulation off the wire easier
Some sort of flap to spread the load from the single grub screw point across the entire wire. Come to think of it, that’d also eliminate the need for fiddly wire 1/2 insulation stripping
Snap on fan mounts to allow adding cooling fans. (hot days, sudden acceleration are both good reasons for this)
OR...make said improvements yourself!
UPDATED LINK for v8.1