This video demonstrates the effect discovered by Thane C. Heins of Potentail Difference Inc.
When a conventional electric motor/generator is loaded it will slow down, due to the counteracting (on the rotor) magnetic field generated in the generator coil windings. The peculiar effect which Thane Heins discovered is that in a special configuration, consisting of a high inductance coil (R=240, L=24) and relatively high frequency(~400 Hz), the back EMF is delayed and the magnetic field reversed, so that instead of counteracting the rotor when the coil is under load, it actually pushes the rotor, leading to a higher RPM and a drop in input power.
This principle seems to have been adopted in electrical bikes by using the back EMF for charging the batteries while driving, thereby extending the range of the battery.
Replication by Jean-Louis Naudin.