Content Comparison

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4.9486    4.8426    4.7182    4.5744    4.4103    4.2254    4.0192

So it seems like the 50S configuration would save 5.3W of power at most under Scenario 1 compared to P45B. 5.3W is like 1.5X a Noctua IPPC 3000 fan at max power….

However, this is all armchair analysis without actual testing done. Ideally, we would have tested a P45B module and a 50S module in a wind tunnel, but I’m not too sure we have the luxury of time to do that now.

To be honest, I think it’s fair to think about the P45B as costing 5.3W of extra power consumption, but providing a much higher thermal performance ceiling for the pack. Does the pack need that extra ceiling? Probably not. But it doesn’t seem like a huge cost to pay for greatly improved thermal benefits (half the temperature rise, 10C higher max charge temp), and a P45B pack can likely still allow us to reduce overall battery system weight from MS15 and won’t massively increase our volume and testing + manufacturing + assembly time like an 18650 pack likely will (since that would massively increase cell count).

Based on what was said above, I think going with a P45B pack is most in line with our MS16 goals of reliability and thermal safety. I wouldn’t be surprised if we eventually learn from doing full testing that a 50S pack would have worked perfectly fine, but P45B gives us a lot more assurance with thermals at a fairly small price (probably 3-4kg extra total added weight). Significantly squeezing weight for the sake of efficiency seems out of scope for this car and is something we can probably aim to do in the future when we have more time and know-how.

I don’t think I specified this above, but a 36S9P pack shouldn’t make a huge change to the volume (so space constraint should be fine) and shouldn’t present any issues with the CG.

And based on the cell selection sheet, the pack should cost $1600, so that is also perfectly within our budget.