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What went right?
Passed all regulations *Reliable
Didn’t break down or anything
It worked
Note: Reliable as in not breaking down after put into the car or being a source of failure. * asterisk is added because the BMS was not very reliable, and we ought to take some responsibility for not completing earlier so Electrical could have done more testing
What could have been better?
DFA
Pack assembly into enclosure was difficult due to interference
Baffles being mounted into the enclosure was difficult due to interference
Module holders being epoxied into the enclosure floor introduced misalignment
Serviceability/Quality-of-Life
Module series-to-series connection was difficult to do and undo
Modules were difficult to install and remove
Hardware mounting on top of batteries made the boards difficult to access for troubleshooting
Quality Control
2 modules had We had an issue with a lot of modules having up to 0.5V -1V imbalance imbalances between parallel groupings and ~6 had 0.2V imbalance between parallel groupings, likely because groups. In the end, we did not test for capacity. At the end, we had maybe 1 module that was suitable to be a back-up replacement, which is a lot of money spent on cells that didn’t go anywhere because we didn’t have the time to make new modules in the endhave enough modules for a pack free of quality issues, which lowered our total pack energy and costed us a lot of time and headache in trying to make replacement modules (which we did not end up having enough time to do).
More rigorous testing & analysis + Reliability
Due to falling behind on timeline and also some general cluelessness from inexperience, we rushed into manufacturing without having a lot of useful test data. Examples: didn’t have any data or calculations on how cooling will go, didn’t do sims on enclosure mounting into chassis, didn’t have data on actual battery pack capacity going into race, didn’t have any data on if vibrations will be an issue given lack of potting or any significant design considerations there (other than battery box sitting on pool noodles). Fortunately things went okay, but this shouldn’t happen again.
Falling behind on timeline also resulted in us not having enough time to properly test our BMS system for reliability.
MS16 Battery Design Constraints & Requirements Overview
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