Eos Battery Bracket Manufacturing
Posted on March 10, 2015 by Toni Carlstrom.
This year, the team is using 18650B type battery cells. The batteries will be held together with ABS plastic brackets. The team chose to manufacture the brackets by milling them out using the CNC machine in the University of Minnesota mechanical engineering student shop. This involved using featureCAM to create tool paths and G-code to run the machine.
A jig was also created so that the blanks could be bolted to a plate and then milled out, four at a time. Despite streamlining the process by creating a fixture, the parts will take the team over two weeks to fully machine because the student shop is only open during business hours, and most team members are full-time students.
Battery brackets on the CNC bed. They are held down with 4 bolts each.
A FeatureCAM screenshot of the program to cut four brackets simultaneously
The battery pack will be assembled by welding nickel shim onto each of the batteries through the bracket. The nickel is highly conductive and easy to weld. Soldering the batteries could damage the cells if they got too hot. The team built a spot-welder which was used on Daedalus and will be used again on Eos. Below is an image of the cutting of the nickel pieces, donated by Diamond Metal Products in Ham Lake. There were some difficulties in cutting out the nickel with the laser, but they were overcome by using a backing material when cutting out the fragile pieces.
Nickel Shim is laser cut at Diamond Metal Products.
A closer image of a completed bracket.