I decided im using ~5000 NiMH AA's for my battery. They have the highest energy density, and they are the cheapest per Watt*hr. They have a ton of surface area for cooling, and would be a light weight alternative to C, D, F cells. They are the most common battery, so I think the most research goes into maximizing their performance. I plan on building 50V 20Ah packs.
Each pack will be fan cooled, and have an array of 20 x 40 cells. 20 cells in parallel should keep the pack balanced, if a cell is dead, there will be 19 others to share the load. If a battery charges sooner, the current will increase to the ones that can still take a charge.
Here is a decision matrix I made.
I plan on using that rotoflex coupling to connect my motor to my transmission.
Cleaned out my engine compartment this weekend. Making good progress!