Battery Module Rev 7 (Final)

Owned by Micah Black
Last updated: Jan 10, 2021
4 min read

This rev of the modules was to change a few of the parts to make it easier to assemble and manufacture.

Main Changes

  1. The adhesive-backed fish paper that was planned to be used was difficult to cut with the diode laser cutter and the university would not let us use the CO2 laser cutters because of valid concerns with vaporizing the adhesive releasing toxic gases. We switched to using a flexible potting compound for this layer instead. This will give even better protection of the spot welds as it fully encapsulates them. It also gives better adhesion between the cell holders and the cells. More details about potting compound can be found here: Potting Batteries. Check out the testing page as well Testing MG Chemicals 8800.
    This potting compound was not modeled in CAD, but goes in the same location as the fish paper was.

  2. Extra clearance was added for the screws that are covered by the gusset plates to ensure that the gusset plates would be able to sit flat against the surface.

  3. Chamfers were added to the edges of the cell holders as well as the positions that the cells will be inserted, making the assembly a lot easier. This was possible since Linamar offered to 3D print the cell holders for us (out of ABS) instead of our original plan to CNC machine them out of acetal. This saved us $800 in material costs and we also didn’t have to worry about making the parts ourselves, which would have been a bit difficult due to the limited access to the bay during COVID.

  4. All M3 bolts were changed to 10mm M3 instead of a mix between 8mm and 10mm. This allows quicker assembly and keeping fewer parts in stock. No design changes were required here.

  5. The Sigma Clad Busbar was modified to have square cutouts and more material removed from the end of it - it doesn’t need to go all the way to the last cell since the nickel will not overlap it out there. The square cutouts allow for more area to be spot welded to better placement of the nickel strips.

  6. The nickel strips finally got the weld projections added to them (not shown in CAD) and the 3D printed die was created to shape them properly. Many revisions of this part were required to get all the sizing correct but it worked great in the end! There is also a negative of this mold that I did not screenshot.

     

  7. A spot for the sponsor name was added to the PCB cover and the connector locations - the one that goes to the module and the one that goes to the AFE were added to the model. They were printed out in dual color like as seen in the screenshot.

     

  8. All of the extra tabs in the balance wire guides were removed since the crossing of wires and all the connectors and heat shrink too more room than anticipated.

     

  9. Fish paper cell separators - these were never added to the CAD (as of Jan 10, 2021), but these were placed in between the series cells within each module, in the locations shown below. This is to reduce the cells rubbing against each other in the event of a crash - the cells have to break this fish paper and both the PVC insulators on the cell cans before creating a short circuit. Also helps in case people drop tools or bolts in the pack and scratch through the insulation.

 

 

I think those were all the changes but I may have missed a few since I’m writing this after all the modules were already manufactured…