On Tue, 03 Jan 2012 14:42:32 +0000, Dave Plowman (News) wrote:
Nope. The ecu senses when the engine has surplus power and uses this to
charge battery. That is why the Mk 3 Prius gets 72.4 mpg.

And when the battery is fully charged, what happens to this 'surplus
power'? Because either it is 'surplus' or it is needed.

It gets dumped back into the grid, via a very long extension cable. And a
supercap.