I reckon you have made some incorrect and possibly damaging or dangerous statements above.

“C -How fast a battery can be charged or discharged. A battery with a discharge rating of 2C would mean you could discharge it at a rate 2 times more than the capacity of the pack, a 3C pack = 3 times more, a 20C pack = 20 times more, and so on.”

The C rating is how fast the battery can DIScharge, not be charged. Charging is usually 1 (1 hour charging time),2…. maybe 5C. There m ay be better, but to say the C rate (discharge) is the charge rate is dodgy.

“The higher the C value the higher the cost usually. What this means to an EV though is how much power you can effectively use. If the C rating is low, you are going to have to use more cells to increase the voltage so that you use less amperage.”

If the C rating is low, then the _last_ thing you want to do is increase the volts “to use less amperage”:
–In fact increasing the voltage will _increase_ the amperage (which is actually what you want through the motor to make it faster). While power is a product of volts and amps, increasing volts also increases amps over a given load. You get less amps from more volts and the same power only if the load draws less current at the new volts. Only if things are balanced in that regard, then you would have the same power at less amps.
– The C rate of batteries is not just about what they can provide the load, due to internal resistance. If you have a C rate of say 20, then that battery will only tolerate a discharge rate of 20 * its AH capacity. It will suffer and maybe burn if you extract much more. LiPos are notorious for this, although now much better protected. That is what would happen if you added more batteries (Volts) without altering the load, to a point where the C rating of the battery was exceeded. This is still caused by internal resistance, which is creating heat in the battery as current flows.
–If you want to increase the current from batteries that have insufficient discharge rate, you need to leave the volts as they are. The paralleled batteries will share the current, not get hot, and provide easier current to the load. This results in more power for the same load.

Nick

I think I found my next Project!