There's no such thing as a "capacitor-based battery". These are two different concepts. Batteries hold a lot of energy, but have slow charging rates. Capacitors charge quickly, but have a lot of current leakage, so they can't hold a charge very long. Some newly proposed capacitors hold more energy, but they're still just capacitors. The thinking I've read about is that cars is that a combination of super-capacitors and batteries could possibly solve the quick-charge problem, but capacitors are also less volume efficient (they're bigger for a given charge capacity). And capacitors have the advantage of not wearing out with successive charges like lithium ion batteries do, so I've read some thinking over the years that capacitors could be the "buffer" that allows batteries to become just an optimally managed pool of watt/hours, and capacitors soak up the transient stuff, like regenerative braking, but I've read nothing lately on recent product plans.
