You are, what, 25 years late? What you describe is the ancient, classic hybrid vehicle, with no plug-in charging. It works and it has always worked due to the fact that internal combustion engine runs at colossally bad efficiency in city traffic conditions (accelerations, idling, etc.), so running the ICE smoothly in optimum conditions, charging batteries with it, and then use that charge to drive an electric motor has better efficiency - plus you can harvest braking energy, too.
These classic hybrids are only useful in city traffic (and occasional longer trips do not hurt too much). Although, I don't see a lot of point in such a 1990's retro thing in 2011+11+1, plug-in hybrids have been available for ages already and even pure EVs are really getting practical.
(I did not check what "Nissan E-Power" is, just replied based to your description.)