Great project - I look forward to following your progress. Since you're using the Tesla drivetrain, why not use Tesla cells too? They are easy to find on EBay, and relatively cheap. They can be reconfigured to double their voltage (so 48v per module instead of 24), allowing you achieve input voltage with only half the modules. It would still cost more than the Volt cells, but would probably double your range. They're also much lighter than the Volt's, giving you better acceleration.