"Dave Plowman (News)" wrote in message
...
In article ,
funkyoldcortina wrote:
The battery can charge while the petrol engine is running - the engine
will run at an RPM suitable for maximum efficiency, not just enough RPM
to drive the wheels. "Spare" power at this RPM goes into recharging the
battery

There is no such thing as 'spare power' under these circumstances. The
only truly free energy in this context is that recovered instead of using
brakes.

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.