You're right, I would only need such discharge times very occasionally: basically only when accelerating from 0-300 in 8.9 seconds, which is a fairly narrow use case. Would it be possible for me to use some sort of capacitor bank that I only charge up then to fulfill peak needs? ... Based on very preliminary calculations and a poor knowledge of how capacitors actually work, I would need a 700 volt, 36 farad capacitor bank.

When you are calculating how much energy you get out of the capacitors, what voltages are you using? Obviously you start at 700 volts, but what voltage do they discharge to?

For instance, if you could completely discharge the capacitors then the energy released would be

E = 1/2*V**2*C

= 1/2*700*700*36

= 8.8 MJ (= 2.4 kWh)

or about 1 MW for 8.8 seconds.

But that's not what is going to happen.

In reality the voltage will only drop as much as the battery voltage drops. If that's 10%, or 70 volts (to 630 V), then the energy released is

E = E

1-E

2
= 1/2*(V

1**2 - V

2**2)*C

= 1.7 MW (= 0.5 kWh)

or about 188 kW for 8.9 seconds

This all assumes that my basic physics is correct and the energy stored in a capacitor is equal to one-half of the product of the voltage squared and the capacitance. But I haven't had my coffee yet today.