My lazy diy battery pack.
The goal here was to make a printed cell holder so that I don’t have to do all this gluing insulating fish paper boring bullshit.
before someone states the obvious . . .YES . . . i know i can buy one and its probably cheaper. however wanted one a particular size and shape and in future i might want to add my own geometry onto this part. im done with waiting for parts during the pandemic.
Design It:
The main thing that makes CAD for this super easy was an idea i had to abuse my Fusion360 Battery Pack Script
First step is to generate the cells. I used 18650 so used 18.6mm diameter and 19.4mm as the spacing (same as standard cell holders)
Next we made another pack where the cells are a few mm narrower but also a few mm longer. this will be the space needed to weld the ends of the tabs.
Then i make a 3rd pack which will be the actual cell holder. The width is the cell width + the desired wall thickness, in my case i used a width of 20.2mm. (20.2 - 18.6/2) = 0.8m wall thickness which is 2 passes of my 0.4mm nosle. height is the desired height of the cell holder, i went 10mm.
i then move the black group down a fraction so that i get a lip on the bottom to hold the batterys in place. I used 0.4mm so that its 2 layers when i print.
Finally i use a combine on the black part to remove all the other cylinders
leaving me with a finished holder. it could be printed as is but i added some fillets for fun.
For the other side i just mirrored this part
Print It
I made 12s6p cause that what cells i had but you should be able to fit up to 12s10p on the Ender 3 print bed.
I printed using PETG for a slightly better temperature resistance and used a brim to make sure things stayed down during printing.
Clean up is not super critical as it wont really be seen inside the pack.
Once you have done both parts (careful cause they are not the same) you can fill it with your cells. I used some recycled E-bike cells i had laying around.
Weld It
To make this super easy im using 25mm nickel and my bodgy malectrics setup.
Nickel seems to push down and make contact well enough. I probably went overboard with the welds but why not.
On the other side I let the positive and negative nickels overhang so that i can solder larger cables onto these tabs.
Im planning to print a case for this but it think a pack using this construction would easily fit in a peli case or similar.