The Denali TorkAtak is the world's first production electric trials bike. It can perform and climb obstacles with power levels similar to a 250cc two-stroke, but it has none of the usage limitations. The TorkAtak will perform fairly rigorous trials manuvers for 20 to 45 minutes on a charge. The supplied charger will restore a charge in about 45 minutes. A generator can power the charger for remote use.
Some generators can recharge the bike directly, with no charger needed.
With a 2 kW generator, charge times can be reduced to as little as 10 minutes, with no battery damage. The small wheels are easily swallowed by the tiniest pothole, and knocked askew by the smallest road bump. While I'm sure that good suspension can do a lot to minimize these problems, I'd still rather start out with a large diameter wheel. The Scoot'Elec is an appropriate answer tot he needs of city dwellers who expect mobility, ease of parking, and clean cities. It performs with complete safety in city traffic.