Watch Video Demonstration here:

http://www.youtube.com/watch?v=hiWwXp95doY

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At this point you can see what happens when I start to pedal the bike powered generator.  The green line goes to a positive value because it is no longer consuming current,  it is now providing current to the system.  The blue line which used to be positive, is no turning negative, which means that the 12V lead acid car battery is actually charging!  

This happened because the voltage at the battery shown by the red and white lines jumped up to about 13Volts DC.  The battery proceeds to charge for about 2 minutes.   You can see that the battery is now providing  50 to 120 watts of power.