How would you initiate the alternator turning on when the battery has dropped too low?
Let me know what you use for a voltage converter since it sounds like an interesting idea. I'd probably need something capable of 300 watts.
Here's a spreadsheet I started putting together a while back. The last tab titled "Cap Calculator" is handy for estimating what a supercap bank alone can do. If you input the farad rating of the caps, it calculates the total series capacitance and if you input the parasitic drain of your vehicle, it can estimate how many hours/days the vehicle can sit before it drains too much to start the vehicle. Just an interesting thought experiment. The spreadsheet can be modified if you download it to your computer.
https://docs.google.com/spreadsheets...it?usp=sharing