Well, that's not exactly true. The Super-caps are super because of their energy density. They pack a lot of capacitance into a much smaller package than previously possible.
However, charging of these capacitors is limited by their internal resistance (very small) and the source resistance of the charger. In the limit, sure, they'll charge "instantly", but only if the charger can deliver almost infinite current. That means big diameter wires, and breakers that don't trip. The governing relationship is I= C*dv/dt. If you want to charge a large capacitor (Big C) rapidly, dv/dt will also be large. So, the two large numbers multiplying each other mean you need a huge short-term charging current availability.
I won't reveal too much of my background, but I have stayed at Holiday Inns in the past.
Well, do they charge a lot faster than a lead acid battery?
In the limit, sure, they'll charge "instantly", but only if the charger can deliver almost infinite current. That means big diameter wires, and breakers that don't trip.
And that would be something like 2.0 gauge cable coming back from the vehicle's motor/alternator?
And what about the concept of using some combination of storage cell, super caps and probably some big-@$$ diodes?
Wouldn’t that perform better than a conventional deep-discharge battery?