I'm not sure what 75Ah cells he refers to ... The closest cells I found on the Dow Kokam web site are:
2C Max Charge Rate
5C max continuous Discharge rate
10C max peak pulse discharge rate
between 1.87 kg and 2.03 kg each
5.8 mm ( +/- 0.3 ) x 455 mm ( +/-2.0 ) x 325 mm ( +/- 2.0 )
Bewteen ~0.802978 Liters to ~0.9115779 Liters each
Between ~138.5 Wh / kg and ~127.5 Wh / kg
Between ~322.5 wh / L and ~284.1 Wh / L
Wayne listed 258 cells in a 3P86S format.
between 1,152 lbs and 1,061 lbs just for batteries + Connections + box + etc.
~208 Liters to ~236 Liters + connections + Box + etc.
If just the batteries were all in one tight mass it could be as small as ~60cm x ~60cm x ~60cm ... or
~23.6 Inches x ~23.6 Inches x ~23.6 Inches.
He listed 318V, 225 ah, 71.5 kWh ...
but the cells spec sheets I could find look more like it would be 318.2V , 210 Ah , ~66.8 kwh.
At 80% DoD ( ~53.4 kwh usable ) that means he needs to average about ~6.5 miles per kwh to make the 350 mile trip in one charge... that will be hard at 55+ MPH highway speeds , including the extra several hundred pounds of weight he is adding to the vehicle.
If he does have 75 Ah cells at 80% DoD that gives him ~57.2 kwh usable of the 71.5 ... which would still need more than ~6.1 miles per kwh at those 55+ MPH highway speeds including the extra several hundered pounds of weight he is adding.
Sounds tight / a close call to me... may or may not make it... will be interesting to see what is average speed ends up being and how much energy he does end up using.
They will eat allot of space ... but if he plans it out carefully , he might be able to make it look nearly OEM and still have 2 full seats and the area above the rear flat OEM IMA cover... from the outside it might not look that different from an OEM Gen-1 Insight.
With the Rear IMA area gutted , spare tire removed, and rear cargo area ... all combined there might just be enough space to make it still look near OEM from the top with the rear IMA hatch cover down ... I would expect him to split up the battery pack though ... putting some in the front, not only for space but to distribute the weight.
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Considering the goal of ~350 Miles ... I think his desire to use 10C discharge rated cells is an error better suited for the drag strip and less so for this specific application.
We won't be able to use that much discharge rate ... and he could have done better than ~138 wh / kg with other types of cells... even if they don't have the 10C discharge rate.
At 100 kw he won't even be pulling 2C ... and even 200 kw won't be over 3C for a 70+ kwh pack.
A Tesla-ish style pack with modern 18650 cells each over 200 wh / kg would have given him significantly more energy ( ~100 kwh ) in the same weight ... or shaved off a chunk of weight for the same capacity.
But I still look forward to see how it comes out... he has done nice work in the past.