Overview
The 2025/2026 FSAE car was designed for coldplates that liquid cool the segments in our tractive battery pack as well as our inverters. I joined this project slightly after the trade decisions between air cooling and water cooling, so I was primarily involved in bringing the design to life. The design of this part was quite simple, but the manufacturing challenges it brought up were much more challenging.
At the competition in Michigan, Northwestern was the only singular team running a water-cooled tractive battery pack. Part of the reason is likely due to the difficulty we found in sealing these plates. Here's some stats from my testing/manufacturing/research:
Hours on a CNC Mill: 120
Bits Broken: 1
Plates Machined: 43
Adhesives Tested: 6
Design Constraints and Challenges
These coldplates needed to be able to hold pressure, survive contact with water, and survive temperatures up to 70 degrees C.
The interior channel design was determined through CFD simulation to find the pressure needed to push the coolant through at the desired speed.
I initially wanted to weld these plates closed, but th ability of our welder combined with the porosity of aluminum welds and the significant warping seen during welding proved this method to not be feasible.
We quickly transitioned to trying different adhesives, and cycled through quite a few including:
DP460
Marine Epoxy
A 2-part RTV product
JB Weld Thermal Epoxy
Outcomes
Using a combination of JB Weld Thermal Epoxy and countersunk bolts to reduce shear peel of the adhesive we were able to produce a set of segment coldplates that could sustain the temperature required at the required pressure. This occurred about 2 hours before we packed the truck for our competition, and I cured the epoxy inside my person oven as a sacrifice.
At the competition, the pack was cooled sufficiently to complete the endurance section for the first time in ten years, and for the first time ever in Formula Racing Electric!
Top: final design of machined coldplate, no top
Bottom: Initial welded and annealed attempt, warping caused chatted on mill that broke through the welded lid