Here's my first thought: Put both supercapacitors and batteries in an electric car. The supercapacitors can help greatly in a couple of ways. When doing a fast charge, the supercapacitor bank can absorb the energy super fast, much faster than a bank of batteries could. Then a microcontroller could control the transfer of that power more gradually over to the battery. (Unfortunately, super capacitors, when I last read something about it, could only hold their charge for 4 days or so, so they couldn't replace batteries themselves.) Perhaps this could be the key to the 5 minute recharge for cars?
Second, supercapacitors could also save some wear and tear on the batteries during rapid acceleration and regenerative charging.
Second, supercapacitors could also save some wear and tear on the batteries during rapid acceleration and regenerative charging.