Came across this post by random chance and though I'd chime in. I oversaw the design of the team's battery and co-designed the BMS that year. I'm really glad people found it interesting!
It's been a while, but I can try to answer a few of the questions:
The electrical isolation material used was commercially available Sil-Pad (thermally conductive electrical insulator). I don't remember the brand or model # in particular, but I believe it had a conductivity of around 3 W/(m-K).
We designed and tested our own fusible link geometry so we could integrate them into the collector plates. The design we settled on was basically a necked down section of material with a "D" shaped tab on the end for welding to the cell. These tabs were pushed down through an insulation plate to make contact with the cell terminal.
We validated the fuses by paralleling a few low voltage high current power supplies together and running current profiles through the links in-situ on a mock-up cold plate to simulate the pack conditions as closely as possible.
One of our concerns was a failure mode where a link could pass enough current to hover near melting point without fusing. This could potentially melt through the sil-pad insulator and break isolation between the pack and cooling plate. The quick and cheap solution we settled on was adding an aluminum heat spreader on top of each collector plate. We tested this and found that it spread the heat evenly enough to not overheat the insulator.
Crapload of wires is right. Almost all of them are going to temperature sensors glued between sets of three cells. The reason for such excessive numbers is that we wanted every sensor location to be double redundant. We knew it'd be an hugeundertaking to attempt maintenance after welding collector plates, and didn't want to risk disqualification if one failed in the future. Only one sensor in each of the 44 sites is actively monitored by the BMS. The wiring took days, but the data was satisfying.
Our pack voltage was directly determined by a motor we already had and a donated charger we could have never afforded on our own (thanks Magna Power http://www.magna-power.com/blog/2016/ba ... ybrid-team
). Having a lower voltage but higher p-count was also nice in terms of single cell failure redundency, even with the hit to efficiency.
suecy's solution is definitely cleaner! Our centralized BMB approach and space limitations made it very difficult to locate sensors at the ends of the cells. If we had more space, it would have been nice to run sensors to the bottoms of each cell (opposite the cooling plate) to monitor the hottest point and increase cell packing density.
coleasterling: Well that's a little harsh, but you are correct. Like many FH teams, we didn't pass tech (though the design of our battery was not the culprit there as far as I know). At least in my time, our team was often guilty of focusing more on fun engineering projects than the challenge of getting a car finished in time with the resources and budget at our disposal
.That was my last year with the team, but the current group of students are working on some really awesome stuff - I'll try to get them to update the blog more than once every 1.5 years.
Sorry for the long post, hope that filled in some of the gaps!